From The History of Philosophy: A Short Survey


James Fieser


Revised 9/1/2017




A. Introduction

From Classical to Medieval

Four Issues for Medieval Philosophers

B. Augustine

Faith, Certainty, Divine Illumination


Evil, Free Will, Foreknowledge

Morality, Proper Desire, Two Cities

C. Pseudo-Dionysius and Boethius

Pseudo-Dionysius: Positive and Negative Religious Language

Boethius: Universals and Divine Foreknowledge

D. Anselm

Ontological Argument

Guanilo’s Criticism

E. Muslim and Jewish Philosophy

Averroes: Resolving Conflicts between Philosophy and Scripture

Maimonides: Interpreting Scripture Non-Literally

F. Aquinas

Twofold Truth and Proofs for God

Divine Simplicity and Religious Language

Morality and Natural Law

G. Scotus and Ockham

Scotus: Divine Illumination, Form-Matter, Divine Command Ethics

Ockham: The Razor and Nominalism

H. Conclusion

Reading 1: Augustine on Plato, the Forms and Divine Illumination

Reading 2: Aquinas on Faith and Reason

Study Questions





For around 1,000 years, the story of philosophy in Europe had been that of the Greek thinkers, beginning with the Presocratics on through those in Hellenistic times. However, as Christianity swept through the Roman Empire, by around 400 CE, the face of philosophy was dramatically changed along with every other cultural institution of the time. This new phase of philosophy also lasted for about 1,000 years, and is called medieval philosophy, named after the medieval period of European history.


From Classical to Medieval

The transition from Greek to medieval philosophy was a rough one, and it exhibits a love-hate relationship that Christian culture had with Greek civilization. On the one hand, Christianity brought with it a cultural and intellectual tradition from the land of Israel that was very much at odds with Greek ways of thinking. At the heart of the difference was the Bible and its central themes of a monotheistic God, life after death, and, perhaps most importantly, the idea of furthering the kingdom of God. As Christian emperors took the throne, they took decisive measures to curb the influence of cultural institutions that conflicted with the Christian message. Orders were given to destroy all pagan temples and shut down schools of philosophy that had been in operation since the days of Plato and Aristotle. On the other hand, however, the new breed of Christian philosophers was greatly influenced by Greek thought, especially the views of Aristotle and Plotinus. While Plato remained a towering figure in medieval times, it was largely in name only since for many centuries copies of his writings virtually vanished. In the absence of actual books by Plato, medieval philosophers looked to Plotinus for a summary of Plato’s views, unaware of how original Plotinus’s views were. Thus, many of the most important views that they attributed to Plato were those of Plotinus. What we find within medieval philosophy, then, is an interesting blend of Greek and Christian views to the degree that thinkers of this period were able to make them compatible.

            Historians mark off medieval civilization as starting with the downfall of the Roman Empire and ending with the founding of the Renaissance—roughly from the years 400-1500. This range of time itself falls into three distinct periods, each of which impacted developments within medieval philosophy. The first period is the early middle ages, from around 400-1000. Often called the “Dark Ages”, it is characterized by tough times in the aftermath of the Roman Empire’s collapse, including localized rule, decreased trade, mass migration, and feudalism. While this timeframe witnessed the Christianization of Europe, Islam was also rapidly enveloping the surrounding regions, and, as with Christianity, Muslims developed their own philosophical tradition that mixed Greek philosophy with their own faith. The next period is the high middle ages, from 1,000 to 1300, which experienced much better times. Population increased, countries and regions regained political cohesion, and intellectual thought was revitalized. Most important for philosophy, though, was the emergence of medieval universities which became centers of learning and gave birth to a distinct philosophical method called scholasticism, which systematically blended philosophy and theology. The final period is the late middle ages, lasting from 1300–1500. Times were again tough with economic stagnation, wars, and the Black Plague that killed around half of Europe’s population. The unity of the Catholic Church also came under fire, which helped bring the middle ages as a whole to a close.


Four Issues for Medieval Philosophers

Throughout the middle ages, four specific issues attracted the attention of its greatest philosophers from the Christian, Muslim and Jewish faith traditions. First is the relation between faith and reason, which involves whether important philosophical and religious beliefs are grounded in the authority of faith, or in reason, or in some combination of the two. One of the most extreme proponents of the faith-only position is the early Church theologian Tertullian (155–230 CE), whose views are encapsulated in two vivid statements that he makes. First, he asks the rhetorical question “What does Athens have to do with Jerusalem?” Athens here symbolizes reason and the tradition of Greek thinking; Jerusalem represents faith, and the doctrines of Christianity that are held by faith. So, what, then does reason have to do with faith? His implied answer is “nothing at all!” His second famous statement is “I believe because it is absurd,” which he wrote when discussing a Christian doctrine about the nature of Christ that went contrary to logic. His point is that reason obstructs our discovery of truth so much that we should expect truths of faith to run contrary to it. Thus, reason is not just a dead end in the pursuit of truth, but it is dangerously misleading. While Tertullian may have been content with the faith-only position, other Christian philosophers held that reason could be an important asset in demonstrating some religious truths that we also know through faith.

            A second issue of interest for medieval philosophers was proving the existence of God. Many medieval philosophers argued that, while we can certainly believe in God on the grounds of faith alone, there are rational proofs that we can also give to show God’s existence. Chief among these is a causal argument:  motion and change on earth trace back to a first cause, which is God. Several versions of this argument were put forward, some with a high level of sophistication. Other proofs for God’s existence where also forthcoming, which used entirely different strategies.

            Third was the problem of religious language. Even if we know that God exists, can we say anything meaningful about him with human words? We commonly describe God using words like “powerful” and “good”, but all of these seem tainted by our limited human experience. Should we give up describing God altogether? Should we reinterpret our descriptions of God in special ways? The solutions that philosophers offered to this problem were both varied and original.

            The fourth issue is the problem of universals, namely whether concepts such as “greenness” and “largeness” exist independently of human thought. The particular tree in front of me is green and large. But there are lots of other particular things that are also green or large, and thus in some sense share the more universal attribute of greenness or largeness. The question, then, is whether universals such as greenness and largeness exist independently of human thought in some external reality, or whether they are just products of the human mind. Medieval philosophers held every possible view on the subject, and in many ways the problem of universals represents medieval philosophy at its best.




The first major medieval philosopher was Augustine (354–430), who emphasized attaining knowledge through divine illumination and achieving moral goodness by loving God. The details of his life are openly laid out in his autobiography, titled Confessions, which even today is considered a classic of world literature. He was born in the North African region of Tagaste to a devout Christian mother and pagan father. For much of his youth, his middle-class parents' greatest concern was affording a university education for him. Once having attained this difficult goal, learning rhetoric at Carthage, Augustine's zeal for studying theology became his driving force. But first came a period of trying out life's alternatives. To his mother’s great displeasure, he became entrenched in a new Persian religion called Manichaeism and then joined a group of Neoplatonists. In both cases he sought to understand how evil could exist in a world that was created by a good God. The Manichaean explanation was that the material world is inherently evil, but through special knowledge from God we can rise above it. Neoplatonists argued that evil results from the physical world being so far removed from God, and thus absent from his goodness.

            For fifteen years he lived with a woman and fathered a son; but when his mother eventually convinced him to marry properly, he left his mistress. While awaiting his bride-to-be's coming of age, he took up with yet another woman and prayed his famous prayer, "Grant me chastity and continence, but not yet." But his marriage to either woman never transpired. While teaching rhetoric in the city of Milan, he attended sermons of the Bishop of that region, which gradually led to his Christian conversion. Returning to North Africa, he was drafted into the priesthood by the locals for his popular preaching, and later became their bishop, devoting the rest of his life to writing and preaching in that region. Augustine died at 75, even as invading barbarian armies were tearing down the city walls of Hippo. Augustine’s literary output was enormous, and he may be the most prolific writer of the ancient world. His most famous writings are his Confessions and The City of God. While only a couple of his shorter works are devoted exclusively to philosophy, most notably Against the Academics and On Free Choice, many of his compositions are interspersed with philosophical content, and from these a complex system emerges.


Faith, Certainty, Divine Illumination

The starting point for Augustine’s philosophy is his stance on the relation between faith and reason. We’ve seen that there are two ways of approaching the relation between faith and reason: first, Tertullian’s faith-only position, and, second, the view that reason by itself can go a long way in establishing religious truths independently of faith. Augustine struck a middle ground between the two, advocating a position that he called “faith seeking understanding.” His inspiration for this was a passage from the Old Testament book of Isaiah “Unless you believe, you will not understand.” On this view, reason by itself is not good enough to give us proper religious knowledge; instead, we have to begin with faith to set us in the right direction and, once we believe in God through faith, we can seek to understand the foundations of our belief through reason.

            A running theme throughout Augustine’s writings is that knowledge is indeed attainable, and we should reject the efforts of philosophical skeptics. By the time Augustine came on the scene, different Greek schools of skepticism were well established, and for centuries had been producing arguments to show that we can no nothing at all for certain. Every belief I have can be brought into question; even my belief that the tree in front of me exists is uncertain since I might just be having a hallucination. In opposition to the skeptics, Augustine argues that there are four main areas in which we have genuine knowledge that even the skeptics cannot question. Right off, each of us has indisputable knowledge of our own existence. He writes,


On none of these points do I fear the arguments of the skeptics of the Academy who say: what if you are deceived? For if I am deceived, I am. For he who does not exist cannot be deceived. And if I am deceived, by this same token I am. [City of God, 11:26]


His point here is simple: no matter how deceived I am—such as through hallucinations or flawed sensory perception—I still have to exist in order to be deceived. This knowledge is so obvious and self-evident that it enables me to go one step further and say that I know that I know. Knowledge is thus an indisputable fact.

            In addition to knowledge of one’s own existence, we also have certainty in three key areas: math, logic and immediate sense experience. Mathematical truths, such as “three times three is nine,” are so compelling that it is impossible to doubt them. So too with logical truths:


I have learned through dialectic [logic] that many other things are true. Count, if you can, how many there are: If there are four elements in the world, there are not five; if there is one sun, there are not two; one and the same soul cannot die and still be immortal; man cannot at the same time be happy and unhappy; if the sun is shining here, it cannot be night; we are now either awake or asleep; either there is a body which I seem to see or there is not a body. [Against the Academics, 3:13]


While Augustine recognizes that sense perceptions themselves are not always trustworthy, he nonetheless maintains that reports of immediate experiences are indisputable, such as “the snow appears white to me.” Even if in reality the snow happens to be a different color, what remains true is that I perceive it as white. He writes:


I do not know how the [skeptical] Academician can refute him who says “I know that this appears white to me, I know that my hearing is delighted with this, I know that this has an agreeable odor, I know that this tastes sweet to me, I know that this feels cold to me.” [Ibid 3:11]


            These areas of knowledge, then, seem to be completely indisputable because of the self-evident nature of their specific truths. There are other areas of knowledge, though, that lack this self-evidence and may indeed be fallible, such as the truths themselves of what our senses report, and also the knowledge that we gain through the testimony of other people. Nevertheless, he argues, in view of how much important information they provide us, we can have reasonable confidence in them as reliable sources of knowledge. Regarding our senses, he argues, “Far be it from us to doubt the truth of what we have learned by the bodily senses, since by them we have learned to know the heaven and the earth, and those things in them which are known to us.” So too with the knowledge that we gain through the testimony of other people. While the reports of some people cannot be trusted, testimony is nonetheless an indispensable source of knowledge. He writes, “Far be it from us too to deny that we know what we have learned by the testimony of others: otherwise we would not know that there is an ocean, or that the lands and cities exist which numerous report mention to us” (On the Trinity, 15).

            Granted, then, according to Augustine we can know many things indisputably and other things with at least a high degree of certainty. But there is still a problem: with our minds being finite, how can we grasp eternal truths which are far beyond our limited natural capacity? His answer is that grasping such truths requires special help from God: God illuminates our minds to enable us to see these truths. Augustine succinctly describes this theory of divine illumination here: “The mind needs to be enlightened by light from outside itself, so that it can participate in truth, because it is not itself the nature of truth. You will light my lamp, Lord” (Confessions, 4:15:25). Truths regarding virtuous living and religious faithfulness are cases in point: “Among the objects of the intellect, there are some that are seen in the soul itself, for example, virtues which will endure, such as piety, or virtues that are useful for this life and not destined to remain in the next, as faith” (Commentary on Genesis, 31:59). For us to grasp these truths, God illuminates our soul, which triggers a special intellectual vision by which we can see them. While Augustine is quite clear that humans stand in need of divine illumination, he is less clear about how this process takes place. Does divine intuition unleash a flood of specific innate ideas in our minds? Is it more like a capacity that allows us to detect and zoom in on the truth? One recent interpretation is that we first develop beliefs on our own, and then God illuminates our minds so that we can see if they are true or false; God provides the justification for our beliefs.



Augustine is one of the first philosophers to have speculated about the nature of time. Time, he says, is something that everyone experiences and is intimately familiar with. We feel the passage of time throughout the day, we note the lengths of time that it takes for things to happen, we can distinguish between short and long amounts of time. However, once we try to explain exactly what time is, we are at a loss. “What then is time? If no one asks me, I know. If I wish to explain it to someone that asks, I do not know” (Confessions 11:14). There are two main ways that we can view the nature of time. First, we might think that it is objective, and part of the external nature of the world itself. Past, present and future are realities. Second, we might think of time as merely subjective, existing only as a product of our minds. While it is tempting to go with the first interpretation, Augustine goes with the second: time has no meaning apart from our minds. The reason is that the past no longer exists, and the future is not yet here. He writes,


These two times then, past and future, how can they exist since the past is gone and the future is not yet here? But if the present stayed present, and never passed into time past, then, truly, it would not be time, but eternity. Suppose that time present (if it is to be time) only comes into existence because it passes into time-past. How, then, can we say that it exists, since its existence is caused by the fact that it will not exist? We can’t truly say that time is, then, except because it tends towards non-being. [Ibid]


It is as though everything that occurs will instantly evaporate with the passing of the present moment.

            The extent to which the past and future are real at all, they must be embedded in the present moment—since the present is all that really exists:


It is now plain and evident that neither future nor past things exist. Nor can we properly say, “there are three times: past, present, and future”. Instead, it we might properly say “there are three times: a present-of-things-past, a present-of-things-present, and a present-of-things-future.” [Ibid 11:20]


When we speak about the past, present and future, we need to connect them all to the present moment. The past involves only memories that we have in the present, and, thus, we should call this the present-of-things-past. The future involves only mental anticipations of what might come, and we should call this the present-of-things-future.


Evil, Free Will, Foreknowledge

Medieval philosophers developed precise notions of God and the attributes that he has, many of which are even now well-known among believers. For example, God is all-powerful (i.e., omnipotent), all-knowing (i.e., omniscient), and all-good (i.e., omni-benevolent). Other commonly discussed attributes of God are that he is eternal, that he is present everywhere (i.e., omnipresent) and that he has foreknowledge of future events. While these traditional attributes of God offer a clear picture of the kind of being that he is, many of them present special conceptual problems, particularly when we try to make them compatible with potentially conflicting facts about the world.

            One of these is the famous problem of evil: how are we to understand God’s goodness in the face of all the suffering that we experience?  It’s clear that suffering is abundant throughout the world, and such suffering is a type of evil. It’s also clear for religious philosophers that God is in control of things, which seems to imply that God is the source of that suffering and evil. But if God is good, then it seems that he cannot be the source of evil. Thus, there is a conflict between God’s power and goodness on the one hand, and the presence of suffering on the other. How can we resolve this conflict? The first step, for Augustine, is to recognize that God has only an indirect role in the cause of some suffering, as he explains here:


[You ask whether God is the cause of evil. In response,] if you know or believe that God is good (and it is not right to believe otherwise) then he does no evil. Further, if we recognize that God is just (and it is impious to deny it) then he rewards the good and punishes the wicked. Such punishments are indeed evils for those who suffer them. Therefore, if no one is punished unjustly (this we must believe since we believe that this universe is governed by divine providence) it follows that God is a cause of the suffering of some evil, but in no way causes the doing of evil. [On Free Choice: 1:1]


For Augustine, God’s goodness means that he does no evil. Yet, God’s justness means that he rewards good and punishes evil. Thus, God indeed causes some suffering through punishment, but he is not the cause of evil actions themselves.

The cause of evil itself, according to Augustine, is the human will, and thus all blame for it rests on our shoulders, not on Gods. We willfully turn our souls away from God when we perform evil deeds:  “look for the source of this movement and be sure that it does not come from God” (On Free Choice, 2:20). Even the punishment that God imposes on us for our evil is something that we brought on ourselves, since “punishment is used in such a way that it places natures in their right order” (On Free Choice, 3:9). Thus, a first solution that Augustine offers to the problem of evil is that human will is the cause of evil and reason for divine punishment. A second and related solution is that the evil we willfully create within our souls is only a deprivation of goodness. Think of God’s goodness like a bright white light; the evil that we humans create is like an act of dimming that light, or shielding ourselves from it to create an area of darkness. It is not like we have created a competing light source of our own, such as a bright red light that we shine around to combat God’s bright white light. Accordingly, the evil that we create through our wills is the absence of good, and not a substantive evil in itself. Augustine writes, “That movement of the soul’s turning away, which we admitted was sinful, is a defective movement, and every defect arises from non-being” (On Free Choice, 2:20). Drawing from Plotinus, “non-being” is Augustine’s term for the complete absence of God.

Yet a third solution to the problem of evil is Augustine’s suggestion that the apparent imperfection of any part of creation disappears in light of the perfection of the whole. To explain, Augustine considers a common objection that God seems to be the source of suffering when our young children die with no clear purpose. His response is this:


In view of the encompassing network of the universe and the whole creation (a network that is perfectly ordered in time and place, where not even one leaf of a tree is superfluous) it is not possible to create a superfluous person. . . . Moreover, who knows what faith is practiced or what pity is tested when these children’s sufferings break down the hardness of parents? We do not know what reward God reserves in the secret places of his judgment for these children . . . . [On Free Choice, 3.27]


Augustine is saying here that troubling events such as the suffering of children are part of a larger system of things in the world, and even these events have a place in contributing to the good of the whole. If we were capable of grasping the entirety of the creation, we would then see the role that each thing plays in the greater scheme of things, contributing to its total perfection.

            The tension between God and evil is just one of the problems surrounding God’s attributes. Another that Augustine considers is the possible conflict between God’s foreknowledge and human free will. If God knows ahead of time what I will do at midnight tonight, then when the time comes I must do that, and thus have no free choice. The problem can be laid out more precisely as follows:


1. If God foreknows all events, then all events happen according to a fixed, causal order.

2. If all events happen according to a fixed, causal order, then nothing depends on us and there is no such thing as free will.

3. God foreknows all events, hence there is no such thing as free will.


Augustine’s solution is to distinguish between two distinct things about my future decisions that God might focus on. On the one hand, God might focus on and foresee my actions, in which case it looks as though my actions are already causally fixed on the timeline. On the other hand, however, God might focus on and foresee what my choice will be, what mental decision I make. By foreseeing my choice, God is focusing on a free will decision that will be left to me in the future. Thus, God's foreknowledge of my actions is dependent upon what my choice will be, and not on my action itself. He explains this here:


Since God foreknows our will, the very will that he foreknows will be what comes about. Therefore, it will be a will, since it is a will that he foreknows. And it could not be a will unless it were in our power. Therefore, he also foreknows this power. It follows, then, that his foreknowledge does not take away my power; in fact, it is all the more certain that I will have that power, since he whose foreknowledge never errs foreknows that I will have it. [On Free Choice, 3:3]


For Augustine, the issue comes down to this. Suppose that I somehow foreknew what choice you would make tomorrow at noontime. Would that necessitate you doing it? Clearly not. Thus, God’s foreknowledge of your choice does not interfere with your freedom any more than my foreknowledge of your choice would.


Morality, Proper Desire, Two Cities

Augustine’s moral philosophy rests on a single theme: desiring all things in their appropriate manner, and reserving our most supreme desire for God. Humans have the capacity to desire things with a wide range of intensity, from very low to very high. According to Augustine, our human psyches are designed in such a way that the highest intensity of desire should be our ultimate love for God. The intensity of our desires for other things—wealth, fame, material goods—should be far less. Our principal moral task is to make sure that all of our desires are properly ordered, that we desire things in the right way. When we fail to do this, our desires become disordered; that is, we desire a lowly thing such as a coat with the intensity that we should otherwise devote to something much higher, even God himself. It is this disordered desire that motivates us to do evil: He writes,


When the miser prefers his gold to justice, it is through no fault of the gold, but of the man; and so with every created thing. For though it is good, it may be loved with an evil as well as with a good love: it is loved rightly when it is loved with proper order; evilly, when disordered. [City of God, 15:22]


            Not only is properly ordered desire central to morality and virtuous conduct, but it is also the cornerstone to a good and just society. Augustine’s political views are mapped out in his book The City of God, which he initially wrote against Roman pagans who blamed the 410 fall of Rome on the domination of Christianity within society and their abolition of polytheistic worship. According to Augustine, we need to see society as consisting of two “cities” or cultures: an earthly one and a heavenly one. The defining difference between the two is that citizens of the earthly city are motivated by disordered desire, while those of the heavenly city have properly ordered desires. He writes,


Two cities have been formed by two loves: the earthly by the love of self, even to the contempt of God; the heavenly by the love of God, even to the contempt of self. The former, in a word, glories in itself, the latter in the Lord. For the one seeks glory from men; but the greatest glory of the other is God, the witness of conscience. The one lifts up its head in its own glory; the other says to its God, “You are my glory, and you lift up my head.” In the one, the princes and the nations it subdues are ruled by the love of ruling; in the other, the princes and the subjects serve one another in love, the latter obeying, while the former take thought for all. The one delights in its own strength, represented in the persons of its rulers; the other says to its God, “I will love you, Lord, my strength.” [City of God, 14:28]


The Roman Empire itself, he argues, is a perfect example of an earthly city that overindulged in disordered desires. This led to immorality, vice, crime, and its ultimate downfall. Citizens of the heavenly city, who have properly ordered desires, realize that the only eternal good is found in God. They live by faith and “look for those eternal blessings which are promised” (City of God, 19:17)

            People of the heavenly city are obviously forced to live here on earth among rival members of the earthly city. However, they consider themselves as resident aliens and follow the laws and customs of the society in which they dwell, but do not settle down to enjoy them. He writes, “So long as the heavenly city lives like a captive and a stranger in the earthly city . . . it does not hesitate to obey the laws of the earthly city, whereby the things necessary for the maintenance of this mortal life are governed” (ibid).  The earthly city at its best seeks peace in this life, a necessary condition for happiness. Accordingly, “the earthly city, which does not live by faith, seeks an earthly peace, and the end it proposes. . . is the combination of men’s wills to attain the things which are helpful to this life” (ibid). The heavenly city makes use of this peace only because it must.




While Augustine was the dominant philosopher of the early middle ages, two others were influential on some specific philosophical issues, namely, Pseudo-Dionysius and Boethius.


Pseudo-Dionysius: Positive and Negative Religious Language

We do not know the real name of the philosopher that today we call “Pseudo-Dionysius.” He was a Christian mystical philosopher living in the fifth century who was influenced by Plotinus view that we should describe God through negative attributes. In his writings he goes by the name “Dionysius the Areopagite,” the Christian convert mentioned in the New Testament book of Acts, who was a member of the Athenian high court. Medieval writers assumed that this was his true identity, scholars now know that this was just a pseudonym, and thus we refer to him as Pseudo-Dionysius. The cornerstone of his religious mysticism is his view that a direct experience of God is so blinding and overpowering that it leaves us in what he calls both an “unapproachable light” and a “dazzling darkness.” The experience is “darkness” insofar as we are incapable of describing anything concrete about it; it is ineffable, meaning that it is unspeakable. Similar to Plotinus, Dionysius maintains that we must describe God by way of negation.

            In his short work titled Mystical Theology, he discusses the limits of religious language and presents a two-step process that we must take when describing God. First, we begin with positive descriptions by which we attempt to say what God is, such as by saying that God is powerful. Second, realizing the inadequacy of our positive descriptions, we then proceed negatively by denying the positive ascriptions that we made; for example, we deny that God is powerful as humans understand the term “power.” Thus, the more we deny our positive descriptions of God, the closer we get to an understanding of God.

            Regarding our positive descriptions of God, Pseudo-Dionysius says that there are three types of descriptions that we can make. First, there are what we can call theological attributes of God, where, as scriptures indicate, we can refer to God as father, son, and holy spirit. These descriptions are profound and seem to point at the very essence of God. However, they are also obscure notions that offer us little detail about God’s nature. Next, there are what we can call philosophical attributes, such as that God is powerful, wise, and good. These are slightly less profound descriptions of God, but at least they give us a bit more detail about God’s nature. Finally, there are blatant human metaphors that we use to describe God, such as with scriptural passages that refer to God as sleeping, angry, grieved, or vengeful. These are the least profound descriptions; they’re trivial and often superfluous. On the other hand, they offer us the greatest amount of detail that we can grasp with our normal human mental capacity.

            So much for our positive descriptions of God. The next step is to recognize that all three groups of these descriptions are flawed and offer distorted views of God. As Plotinus suggested, God himself is incapable of direct description because of his pure and simple perfection, and the best we can do is describe God negatively—by saying what he is not. Pseudo-Dionysius agrees, and suggests that we begin by denying the blatant human metaphors that we use to describe God: he has no emotions as humans understand them. Thus, we must recognize that he is not “a body, nor has he form or shape, or quality or quantity or mass; he is not localized or visible or tangible; he is neither sensitive nor sensible; he is subject to no disorder or disturbance arising from material passion” (Mystical Theology, 4). By denying these particular features of God, a more accurate image of him emerges. It is much like how a sculptor begins by chipping away at a block of stone, removing the parts that aren’t quite right, and eventually produces a clear image of a statue. Next we deny the philosophical attributes: he is not power, knowledge, or goodness as humans understand the terms. Finally, we deny theological attributes: he is not father, son, or holy spirit as humans understand the terms.

            Through these successive steps of first affirming then denying God’s attributes, Pseudo-Dionysius  argues that we climb ever higher towards an understanding of God that rests on a mystical experience of the divine as we approach him. God himself, though, can never be adequately described: “for the perfect and sole cause of all is above all affirmation, and that which transcends all is above all subtraction, absolutely separate, and beyond all that is” (Mystical Theology, 5).


Boethius: Universals and Divine Foreknowledge

Boethius (480-524) is best remembered for his theory of universals which set the conceptual framework for discussion on that topic throughout the middle ages. He was born in Rome to a wealthy Christian family, but soon after orphaned, he was raised by his adopting family with a great appreciation for Greek and Roman culture, at a time when Rome was ruled by barbarian kings. He was well acquainted with classical philosophy, particularly Plato, Aristotle and Neoplatonism, and his extensive knowledge made him a valuable asset to the royal government. Quickly moving up the ranks in administrative posts, his career came to an abrupt end when he was accused of treason and executed. While in prison he wrote his most influential work, The Consolation of Philosophy.

            Boetheus has the honor of being the first medieval philosopher to systematically explore the problem of universals, that is, the question of whether abstract notions such as “greenness” exist somewhere in reality or only in our minds. He got his inspiration from a brief comment about universals made by the Neoplatonist philosopher Porphyry:


I shall avoid investigating (a) whether genera and species [i.e., universals] are real or are exist merely in thoughts, (b) if real, whether they are material or immaterial, and (c) whether they exist separately from sensible things or have their reality in connection with them. Such business is profound, and requires another, greater investigation.  [Introduction to Aristotle’s Categories]


In the above passage Porphyry questions different ways in which universals might exist, and Boethius responds by suggesting three possible positions on the subject. The first position is that universals such as “greenness” exist outside of our minds and even separately from physical bodies such as a green tree. This is the classic position taken by Plato who held that abstract notions such as “greenness” exist in the non-physical realm of the Forms. The term for this option is “universals ante rem”, Latin for “before the thing.” Position two is that universals are intrinsic—or built into—physical things. For example, the universal “greenness” is found in all green individual objects, such as trees and grass. This is the view taken by Aristotle, and the term for this position is “universals in re", Latin for “in the thing.” The third position is that universals exist only as concepts in the human mind, and not in any real way in the external world. We abstract them from particular things, such as when after viewing several green trees I form the mental abstraction of “greenness”. The official term for this is “universals post rem”, Latin for “following the thing.” These three positions on universals, as laid out by Boethius, became the definitive options of further discussion on the subject by later medieval philosophers as they defended one of these positions against the others. So, which of these three views did Boethius think is right? It’s not clear. He criticizes them all on various grounds, and seems to endorse aspects of each. In one of his writings he endorses a combination of Aristotle’s view and the mental abstraction view: universals exist within individual objects, but also exist in our minds as abstractions when we think of those individual things. In another work, though he holds Plato’s view that universals exist in a non-physical world, apart from individual objects and our minds.

            Boethius was influential on one other major philosophical issue, that of the conflict between divine foreknowledge and free will. Again, the problem here is that if God knows what I will do before hand, then that event must happen, and I have no free will to do otherwise. Boethius has an ingenious solution to this problem: God stands outside of time and thus knows what I will do by viewing the whole timeline at once; this does not constrain our free choices. This solution rests on a unique conception of God’s attribute of eternality. Consider these two conceptions of what it means to be eternal: (1) endless existence on the timeline, and (2) existence completely outside of time. To say that God is eternal in the first sense means simply that at any point that you pick in the timeline, God existed or will exist. God moves through time along with me and everything else in the world. The second notion of eternality places God completely outside of the timeline and suggests that the phenomenon of time does not even apply to God. Boethius goes with this second notion of God’s eternality: “eternity is the possession of endless life, whole and perfect at a single moment” (Consolation of Philosophy, 5:6).

            Once we adopt this second view of God’s eternality, according to Boethius, the conflict between foreknowledge and free will disappears. God does not foresee my future actions by peeking down the timeline with a special telescope. Rather, he inspects the entire timeline at once, which includes my free will choices at the moments that I make them.


Since God stands forever in an eternal present, his knowledge, also transcending all movement of time, dwells in the simplicity of its own changeless present. It embraces the whole infinite sweep of the past and of the future, contemplates all that falls within its simple cognition as if it were now taking place. And therefore, if you will carefully consider that immediate presentment whereby it discriminates all things, you will more rightly conclude that it is not foreknowledge as of something future, but knowledge of a moment that never passes. . . . Thus, the divine anticipation does not change the natures and properties of things, and it beholds things present before it, just as they will hereafter come to pass in time. [Ibid]


For Boethius, then, it is misleading to even call this divine “foreknowledge” since this wrongly implies that God is looking into the future. Instead, it is an “outlook” that “embraces all things as from some lofty height” (ibid).




Anselm (1033–1109) made his mark in the history of philosophy for developing what is now called the ontological argument for God’s existence. He was born to a noble family, owners of considerable property in the city of Aosta in the Italian Alps. His virtuous mother faithfully provided young Anselm with religious training and inspired in him a love of learning. In contrast, his father was a harsh man with a violent temper. At 14 years of age Anselm sought admission to a monastery, but the abbot, fearing trouble from his father, refused him without paternal permission. The boy was so desperate, he prayed for an illness, hoping the monks would pity him and change their minds. He got half his wish. He became ill, but was still not accepted. This, and the death of his mother, resulted in Anselm leaving his studies for a more carefree life. By age 23, he could take his father’s abuse no longer and left, wandering for three years through the region. He then entered the Benedictine abbey at Bec, Normandy, as a novice, and in a few short years became its Prior. He was later enthroned as archbishop of Canterbury. However, when the King refused to free the church from royal control, Anselm went into exile in protest. When the King died, the subsequent ruler called Anselm back, but the terms were no different, and so Anselm remained in exile. Throughout this time he wrote many short works. At the time these did not receive their deserved appreciation, but are now considered great achievements. Anselm’s writings are in the form of dialogues and meditations, the most important of which are his Monologium and Proslogium.

            Anselm followed Augustine’s view of the relation between faith and reason: faith seeking understanding. Thus, Anselm writes “I hold it to be a failure in duty if after we have become steadfast in our faith we do not strive to understand what we believe." In his effort to understand his faith, he was consumed with the idea of proving God’s existence, and, in his first effort to do so, he offers a proof from absolute goodness. He presents the basic intuition behind this argument here:


Since there are goods so innumerable, whose great diversity we experience by the bodily senses, and discern by our mental faculties, must we not believe that there is some one thing, through which all goods whatever are good? [Monologium 1]


More formally, his argument is this:


1. Goodness exists in a variety of ways and degrees.

2. This would be impossible without an absolute standard of good, in which all goods participate.

3. Therefore, an absolute standard of good exists, which is God.


The argument takes its inspiration from Plato’s view of the Form of the Good. According to Plato, all good things that we see around us—a good person, a good photograph, a good meal—obtain their goodness by participating in the perfect form of Goodness that exists in a non-physical realm. Anselm agrees, and he draws attention to the fact that the same kind of things often differ in their degree of goodness. Some people are very good, others not so much. Some meals are good, others not so much. The standard of goodness, then, must come from some outside source which is always perfectly good, and that perfectly good source is God.


Ontological Argument

Although Anselm believed that this argument successfully proved God’s existence, he also felt that it was a little too cluttered. It first requires us to experience various good things in the world, then assess their differing levels of goodness, then finally draw the conclusion. Perhaps, Anselm thought, he could do better and construct a more self-contained argument: “I began to ask myself whether there might be found a single argument which would require no other for its proof than itself alone” (Proslogium, Preface). This indeed is what he accomplished in his Ontological Argument for God’s existence, which even today stands as one of the greatest arguments in the history of philosophy. It doesn’t require us to experience anything through our senses. Rather, it simply begins with a definition of God, and draws its conclusion directly from that definition. Although the argument is self-contained, it is a bit challenging to grasp its central point as he presents it here:


Even the fool [who says in his heart there is no God] is convinced that something exists in the understanding, at least, that than which nothing greater can be conceived. For, when he hears of this, he understands it. And whatever is understood, exists in the understanding. And assuredly that than which nothing greater can be conceived, cannot exist in the understanding alone. For, suppose it exists in the understanding alone: then it can be conceived to exist in reality; which is greater.

            Therefore, if that than which nothing greater can be conceived, exists in the understanding alone, the very being, than which nothing greater can be conceived, is one, than which a greater can be conceived. But obviously this is impossible. Hence, there is no doubt that there exists a being, than which nothing greater can be conceived, and it exists both in the understanding and in reality. [Proslogium, 2]


Worded more simply, his argument is this:


1. God is defined as “The Greatest Possible Being.”

2. The Greatest Possible Being must have every quality that would make it greater (or more superior) than it would be otherwise.

3. Having the quality of real existence is greater than having the quality of imaginary existence

4. Therefore, the Greatest Possible Being must have the quality of real existence.


Premise one gives a definition of God. Anselm’s actual wording is that God is “that than which nothing greater can be conceived,” which more concisely means simply that God is the greatest possible being. Premise two rests on the notion of a quality that makes something great: to possess it makes you greater than to lack it. Having the quality of strength makes a bridge greater than it would be if it lacked it. Having the quality of healthiness makes me greater than I would be if I lacked it. By definition, the “Greatest Possible Being” must have every quality that would make it great. Premise three states that “existence” is a quality that makes something great. Having a real gold coin in my pocket is greater than just imagining to have one. By existing in reality, I am greater than I would otherwise be if I only existed in someone’s imagination. The conclusion that follows is that the Greatest Possible Being must have the quality of real existence: if it lacked it, it could have been greater. That is, it would be the “Greatest Possible Being that could have been greater,” which is a contradiction.

            Anselm recognizes that “existence” is just one quality that makes something greater than it would be otherwise. Another such quality is ultimate power, and, thus, we can reword premise 3 with this quality:


3.1. Having the quality of ultimate power is greater than having limited power.


Thus, the Greatest Possible Being must also have the quality of ultimate power. So too with ultimate wisdom, and ultimate goodness. Anselm writes that the Greatest Possible Being is “just, truthful, blessed, and whatever it is better to be than not to be. For it is better to be just than not just; better to be blessed than not blessed” (ibid, 3). Anselm uses this strategy to show that, not only does the Greatest Possible Being exist, but it exists necessarily; that is, it would be impossible for him to not exist—or, as he words it, “it cannot be conceived not to exist” (ibid). Thus, again, we can reword premise 3 with this quality:


3.2. Having the quality of necessary existence is greater than having contingent existence.


The term “contingent existence,” as used above, refers to things that just happen to exist, but don’t need to exist, such as me, the chair I’m sitting on, and every other physical thing in the world. That is, we can conceive of a universe where none of these things existed. By contrast, necessary existence has to do with things whose non-existence is impossible. Mathematical concepts such as 2+2=4 might be examples of these, since it is impossible for these notions to be false. Anselm’s point above is that necessary existence is superior to mere contingent existence, and thus the Greatest Possible Being must have the quality of necessary existence.


Guanilo’s Criticism

As Anselm’s writings circulated, a monk named Guanilo had trouble accepting Anselm’s argument. While Guanilo certainly believed that God existed, he felt that Anselm’s argument was flawed, and thus tried to expose the problem. Guanilo suggests that we should imagine a mythological “lost island” that we might define as “The Greatest Possible Island”. By plugging this definition into Anselm’s ontological argument, we could then prove the existence of that island. Guanilo writes,


You can no longer doubt that this island which is more excellent than all lands exists somewhere, since you have no doubt that it is in your understanding. And since it is more excellent not to be in the understanding alone, but to exist both in the understanding and in reality, for this reason it must exist. For if it does not exist, any land which really exists will be more excellent than it; and so the island already understood by you to be more excellent will not be more excellent. [Ibid, Guanilo]


Following the argument structure above, the parallel argument that Guanilo offers is this:


1. The Lost Island is defined as “The Greatest Possible Island.”

2. The Greatest Possible Island must have every quality that would make it greater (or more superior) than it would be otherwise.

3. Having the quality of real existence is greater than having the quality of imaginary existence.

4. Therefore, the Greatest Possible Island must have the quality of real existence.


The larger point of Guanilo’s criticism is that Anselm’s type of argument is so flawed that it would show the existence of the greatest possible anything—the Greatest Possible Shoe, the Greatest Possible Unicorn, the Greatest Possible Eyebrow.

            Anselm gave an extensive reply to Guanilo, attempting to show that the argument format only works with “The Greatest Possible Being” and not with things like islands.


That being alone, on the other hand, cannot be conceived not to exist, in which any conception discovers neither beginning nor end nor composition of parts, and which any conception finds always and everywhere as a whole. . . . So, then, of God alone it can be said that it is impossible to conceive of his non­existence; and yet many objects, so long as they exist, in one sense cannot be conceived not to exist. But in what sense God is to be conceived not to exist, I think has been shown clearly enough in my book. [Ibid, Reply]


Anselm’s reply seems to be this. The argument structure only works with “the Greatest Possible Being,” since only “being” is capable of having ultimately great qualities, such as necessary existence. An island, by contrast, is a finite and limited thing that is composed of parts, and is thus incapable of having ultimately great qualities. The very notion of “The Greatest Possible Island” is self-contradictory since it attempts to impose the greatest possible qualities on a finite thing. Again, only the notion of “being” is capable of having ultimately great qualities piled onto it. Thus, only one version of the argument works—the one that focuses on the greatest possible being—and this is an argument that proves specifically proves the existence of God.




As Christianity spread throughout Europe, pagan religions diminished and all but disappeared. However, two other religious traditions persisted in the region, namely Judaism and Islam, in spite of continual efforts of Christian rulers to suppress them through war, relocation, or forced conversion. While the political relations between the three religious traditions were hostile, there was more compatibility between them philosophically. One reason is that all three of those religions share a common monotheistic view of an all-powerful, all-knowing, all-good God who created the world and watches after us. Because of this doctrinal commonality, philosophers within the three traditions focused on many of the same issues: the relation between faith and reason, proofs for God’s existence, and the meaningfulness of religious language. While Judaism and Islam each have a complex and philosophically rich history, we will only look at the views of two figures: the Muslim philosopher Averroes, and the Jewish philosopher Maimonides.


Averroes: Resolving Conflicts between Philosophy and Scripture

Averroes is the Latin name of the Spanish-Muslim philosopher Ibn Rushd (1126-1198), who is remembered for his view that philosophers are best suited to interpret scripture. He was born into a prominent family of judges in Cordova Spain, which was then under Arab control. Schooled in philosophy, Islamic Law and medicine, he made a name for himself in all three of these areas throughout his life. In philosophy he was commissioned to write commentaries on Aristotle’s works. Following in the footsteps of his father and grandfather, he was Cordova’s chief judge for several years. Later on he became the personal physician to the ruler of Spain and Morocco. In spite of his distinguished career, near the end of his life he was forced into exile on grounds of heresy, and his books were burned. He was permitted to return two years later, but died the following year.

            One of his most influential works is A Decisive Treatise, which addresses the question: what should we do when scripture conflicts with demonstrative truths of philosophy and science? For example, scripture might hold that God created the world at a particular moment in time; philosophy, on the other hand, might hold that the world has existed from eternity past and was not created at any moment in time. Which view should we follow? His answer is that we should accept the demonstrative truth established by philosophy and seek for a metaphorical interpretation of scripture that will make the apparent conflict disappear. He writes,


If the [scriptural] Law speaks of it, either it will agree with that which has been proved by [philosophical] inference, or else it will disagree with it. If it is in agreement it needs no comment, and if it is opposed to the Law, an interpretation is to be sought. Interpretation means to carry the meaning of a word from its original sense to a metaphorical one. But this should be done in such a manner as will not conflict with the custom of the Arabian tongue. It is to avoid the naming of an object, by simply mentioning its like, its cause, its attribute, or associate, etc. which are commonly quoted in the definition of the different kinds of metaphorical utterances. [Decisive Treatise]


According to Averroes, the problem arises since not all people have the same intellectual capacity to understand scripture: some people can understand logic, while the vast majority cannot. To address the wide range of readers, God crafted scriptures with two levels of meaning. First, there is the common or “exoteric” meaning of scripture that relies on catchphrases, buzzwords, stories and parables. Ordinary readers tend to understand these literally. Second, there is the true meaning of scripture which is hidden or “esoteric”, and requires interpretation. Between these two main levels of meaning there is a blurry middle ground:


There is a third part of the Law which occupies an intermediate position, on account of some doubt about it. Some say that it should be taken exoterically, and that no interpretation should be allowed in it; while there are others who say that they have some of esoteric meaning, and should not be taken exoterically by the learned. This is on account of the obscurity of their meaning. A learned man may be excused if he makes a mistake about them. [Ibid]


Thus, with some scriptural passages it’s not clear whether they are only exoteric and must be understood literally, or whether they are esoteric and need further interpretation.

            According to Averroes, there are three groups of people who seek to understand scripture. First there are the masses of people, who are guided only by catchphrases and buzzwords, and thus take scripture literally. Second, there are dogmatic theologians who attempt some interpretation, but don’t have the skill to arrive at the true meaning. Finally, there are the philosophers who, through their studies of logic, have the ability to draw the proper inferences. In fact, their skill is so specialized that they should not even discuss their interpretations with the masses or the dogmatic theologians:


This kind of interpretation should not be discussed with the dogmatic theologians, not to speak of the common people. If any of these interpretations are disclosed to those not fit to receive them--especially philosophical interpretations--these being far higher than common knowledge, they may be led to infidelity. [Ibid]


Ultimately, it is the philosopher who has the logical ability to properly interpret scripture.

            In short, Averroes maintains that apparent conflicts between philosophy and scripture can be resolved by adopting metaphorical interpretations of scripture that skilled philosophers are capable of drawing. Although his position might be a little elitist—and might give too much credit to philosophers’ logical abilities—it offers a consistent way of resolving potential conflicts between philosophy and scripture. While Muslim followers of Averroes’ philosophy embraced his solution to this problem, it also had a great influence on Christian philosophers of the time called “Latin Averroists”, who modified it into a position called the doctrine of double truth. According to this position, there are two levels of truth, one in philosophy and one in religion, and what is true in philosophy could be false in religion, and vice versa. Again, suppose that scripture states that God created the world at a particular moment in time, while philosophy holds that it is eternal. The double truth doctrine maintains that each of these positions is true in its own realm, even though they contradict each other. Averroes himself never went this far, and suggests instead that there is really only one truth, which can be accessed differently by the masses, dogmatic theologians and philosophers. The rather controversial doctrine of double truth devised by the Latin Averroists was ultimately condemned by the Catholic Church in the 13th century.


Maimonides: Interpreting Scripture Non-Literally

Moses Maimonides (1135-1204) was a Spanish-Jewish philosopher who rejected literal interpretations of scripture in favor of allegorical ones. Maimonides was born in Cordova Spain, which under Muslim rule was at the height of that country’s cultural achievement. He was schooled in Greek and Arabic philosophy, Jewish law, and later in medicine. An anti-Jewish political shift in Cordova forced Maimonides into exile, which prompted him to live for a time in Morocco, Palestine, and then permanently in Egypt. After the death of his father and wealthy brother, financial problems pushed him into the field of medicine and he became physician to the court of an influential military general. Maimonides’ most famous philosophical work is the Guide for the Perplexed, which is written as a three-volume letter to a student. The work addresses sensitive subjects, such as religious language and God’s creation of the word, which led some Jewish officials of the time to ban or condemn it. Originally written in Arabic, the Guide was shortly after translated into Hebrew and Latin where it had a great influence on Christian philosophers.

            The main goal of Maimonides Guide for the Perplexed is to liberate religious believers from interpreting the Bible literally. Throughout the Bible, some words are indeed meant to be taken literally, and others should be understood figuratively. The difficulty is determining which words should be viewed in which way. He writes:


My primary object in this work is to explain certain words occurring in the prophetic books. Of these some are homonyms, and of their several meanings the ignorant choose the wrong ones; other terms which are employed in a figurative sense are erroneously taken by such persons in their primary [literal] signification. There are also hybrid terms, denoting things which are of the same class from one point of view and of a different class from another. [Guide for the Perplexed, Introduction]


According to Maimonides, religious tradition often wrongly imposes literal interpretations on scriptures, such as with passages that depict God as having human-like emotions. While such literal interpretations seem odd to intelligent believers, they nevertheless feel trapped into accepting the literal interpretation out of religious duty. This places believers in a state of anxiety:


It is not here intended to explain all these expressions to the uneducated. . . .  The object of this treatise is to enlighten a religious man who has been trained to believe in the truth of our holy Law, who conscientiously fulfils his moral and religious duties, and at the same time has been successful in his philosophical studies. Human reason has attracted him to abide within its sphere; and he finds it difficult to accept as correct the teaching based on the literal interpretation of the Law, and especially that which he himself or others derived from those homonymous, metaphorical, or hybrid expressions. Hence he is lost in perplexity and anxiety. [Ibid]


His book is thus titled A Guide for the Perplexed, and aims to help put an end to over-literalizing scriptural interpretations, thus freeing the believer from anxiety.

            To accomplish his task, Maimonides painstakingly analyzes scores of Hebrew words in the Bible which, when taken in the wrong way, could mislead readers into interpreting the Bible too literally. His very first example concerns the passage in the book of Genesis where, when creating Adam, God says “Let us make man in our image”. The Hebrew word for “image” in this verse is zelem, and an overly-literal understanding of the word has led many believers into holding that God has a physical body, shaped like a human one with a face, hands and legs:


Some have held the opinion that by the Hebrew word zelem [i.e., image] means the shape and figure of a thing, and this explanation has led some to believe in the corporeality of God [i.e., that God has a physical body]. For they thought that the words “Let us make man in our zelem [i.e., image]” implied that God had the form of a human being, that is, that He had figure and shape, and that, consequently, He was corporeal. They adhered faithfully to this view, and thought that if they were to reject it they would by doing so reject the truth of the Bible. And further, if they did not conceive God as having a body possessed of face and limbs, similar to their own in appearance, they would have to deny even the existence of God. [Ibid 1.1]


The solution, for Maimonides, is to realize that the term there “image” (zelem) in this passage doesn’t mean physical form, but only the essence of a thing. There is in fact another Hebrew word that does mean “physical image” – the word toar – but the passage from Genesis doesn’t use it, preferring instead zelem:


I hold that the Hebrew equivalent of [physical] “form” in the ordinary use of the word, that is, the figure and shape of a thing, is toar. Thus we find “[And Joseph was] beautiful in toar [i.e., physical form], and beautiful in appearance” (Gen. 39:6). . . This term is not at all applicable to God. The term zelem, on the other hand, signifies the specific form, that is, that which constitutes the essence of a thing, whereby the thing is what it is; the reality of a thing in so far as it is that particular being. [Guide for the Perplexed, 1.1]


            With other scriptural passages Maimonides takes a different approach when stripping them of their overly-literal meanings. There are, for example, verses that describe God as “merciful” or “angry”, both of which are human-like emotions. His solution here is to interpret these statements as expressing qualities that we see in God’s creation of the natural world, but not as psychological qualities of God himself. For example, the statement that “God is merciful” really means that the natural world as created by God displays merciful characteristics. It gives us nourishment and works in ways that make our lives pleasant. Similarly, the statement “God is angry” really means that the natural world as created by God is severe towards people when they act improperly.




Perhaps the leading philosopher of the middle ages was Thomas Aquinas (1225–1274), who maintained that reason, unaided by faith, can give us knowledge of God’s existence and an understanding of morality as it is grounded in natural law. At his family’s castle in Naples, Italy, Thomas Aquinas was born to nobility on both sides, being a son of Count and a relative of a dynasty of Holy Roman emperors. His education began at age five at a monastery where his uncle was abbot, and expectations were high that Aquinas would one day fill that position. He was later transferred to the University of Naples, where he became acquainted with the Dominicans and, to his family’s horror, resolved to join them. At 18, he set off for Rome, but was seized by his brothers, returned to the family castle, and held captive while the family prayed, threatened, and even tempted him with a prostitute, hoping to change his mind. They could not. A year later the family yielded under pressure from the Pope, and Aquinas was sent to Cologne to study under some of the great philosophers of the time.

            While Aquinas was described as refined, affable and lovable, he was physically big, solemn and slow to speak, earning him the nickname of the Dumb Ox. A story relates that Aquinas's colleagues teased him saying that there was a flying cow outside, and when he looked out the window they laughed. Aquinas responded that he would rather believe that a cow could fly than that his brothers would deceive him. During his subsequent education, apprenticeship, and public business in the church, he became famous for religious devotion and excellent memory, having memorized much of the Bible. The church offered to make him an archbishop and an abbot, but he refused both, preferring his studies. He composed book after book until he had a mystical experience that compelled him to cease writing altogether. Traveling to attend a Church Council, he became ill and died. Fifty years later he was canonized as a saint despite the lack of traditional saintly manifestations—stigmata, miracles, mortifications—which were waived in lieu of his outstanding contribution to the Church. His philosophical writings commentaries on Aristotle and his most important work, the multi-volume Summa Theologica (Latin for “theological synopsis”).

            Aquinas wrote in a formal and technical style that was common during this period of medieval philosophy. From the time of Augustine, medieval philosophy had a mystical and intuitional component to it. We’ve seen this specifically with Augustine’s motto “faith seeking understanding” and Pseudo-Dionysius’ view that through denying our notions of God we ascend higher in our experience towards him. The larger message of this earlier period was one of warning: reason is all well and good in its proper context, but it should not replace the more religiously intimate element of faith. Around 1100, though, this gave way to a more rationalistic approach that emerged within medieval universities called scholasticism, meaning the method of the “schools”. The goal of scholasticism was to systematically bring philosophy into dialogue with theology through a very specific methodology. Philosophical texts would no longer be written as prayers to God or meditations, but rather in a much more scientific-like manner. Precise questions would be posed, followed by a critical analysis of previous philosophers’ views of the subject. Subtle distinctions would be made to help clarify problems. Through this critical analysis, rationally-informed answers to the questions would emerge. Some medieval philosophers, such as Anselm, were transitional figures with their feet in both genres. Aquinas’s writings, though, fully embody the scholastic approach.


Twofold Truth and Proofs for God

Like other medieval philosophers, Aquinas’ philosophy starts with a view of the relation between faith and reason. For a religious believer, faith in God and scripture is of course fundamental. However, he argues, many basic religious truths such as God’s existence can be proven without faith and through reason alone. Accordingly, he proposes a view of faith and reason which he calls the twofold truth: while reason can give us some truth, other truths can only be attained through faith. He writes,


The truths that we confess concerning God fall into two categories. Some things that are true of God are beyond all the competence of human reason, such as that God is three and one. There are other things to which even human reason can attain, such as the existence and unity of God, which philosophers have proved to a demonstration under the guidance of the light of natural reason. [Summa Contra Gentiles, 1.3]


The first class of truths that are accessible through reason alone he calls presuppositions of faith, which include the truths that God exists and God is one. The second class of truths, called mysteries of faith, are accessible only through faith and involve doctrines like the Trinity, which we learn about in scripture and are central to the Christian faith in particular. Human reason alone cannot access these truths, he argues, since, in our present life “knowledge and understanding begins with the senses” (ibid). While this prevents us from knowing God’s inner nature, our senses can still give us information about creation which allows us to infer that there is a powerful and designing creator to all that we see.

            Again, one of the things that we can know through reason alone is that God exists, and to that end Aquinas offers five ways of proving God. Briefly, they are these:


1. There must be a first mover of things that are in the process of change and motion.

2. There must be a first efficient cause of the events that we see around us.

3. There must be a necessary being to explain the contingent beings in the world around us.

4. There must be an ultimately good thing to explain the good that we see in lesser things.

5. There must be an intelligent being who guides natural objects to their ends or purposes.


The first three of his proofs share a similar strategy, which was inspired by Aristotle’s notion of the unmoved mover: there is a first cause of all the motion that takes place throughout the cosmos. In more recent times this argument strategy has been dubbed the cosmological argument. We’ll look specifically at Aquinas’s second argument from efficient cause as he presents it here:


The second way is from the nature of the efficient cause. In the world of sense we find there is an order of efficient causes. There is no case known (neither is it, indeed, possible) in which a thing is found to be the efficient cause of itself; for so it would be prior to itself, which is impossible. Now in efficient causes it is not possible to go on to infinity, because in all efficient causes following in order, the first is the cause of the intermediate cause, and the intermediate is the cause of the ultimate cause, whether the intermediate cause be several, or only one. Now to take away the cause is to take away the effect. Therefore, if there be no first cause among efficient causes, there will be no ultimate, nor any intermediate cause. But if in efficient causes it is possible to go on to infinity, there will be no first efficient cause, neither will there be an ultimate effect, nor any intermediate efficient causes; all of which is plainly false. Therefore it is necessary to admit a first efficient cause, to which everyone gives the name of God. [ST 1, Q. 2, Art. 3]


According to Aquinas, we experience various kinds of effects in the world around us, and in every case we assign an efficient cause to each effect. The efficient cause of the statue is the work of the sculptor. If we took away the activity of the sculptor, we would not have the effect, namely, the statue. But there is an order of efficient causes: the hammer strikes the chisel which in turn strikes the marble. But it is impossible to have an infinitely long sequence of efficient causes, and so we arrive at a first efficient cause.

            Aquinas’s argument from efficient cause is deceptively brief, and he appears to be offering the same argument that early Muslim philosophers did in the so-called Kalam argument for God’s existence. That is, it seems as though he is saying that it is impossible to trace such causal connections back through time and, ultimately, we must arrive at a first cause, namely, God. However, other writings by Aquinas make it clear that he is doing something different. Why, at least in theory, couldn’t this causal sequence trace back through time, to infinity past, and never have a starting point? Although this may be a strange contention, there is nothing logically contradictory about it. He writes that “It is by faith alone that we hold, and by no demonstration can it be proved, that the world did not always exist” (ST 1, Q. 46, Art. 2). Aquinas suggests that we view the causal sequence somewhat differently. Some causal sequences do indeed take place over time, such as when Abraham produces his son Isaac, who later produces his own son Jacob. But in addition to these time-based sequences, there are also simultaneous causal sequences, which do not trace back through time. Imagine, for example, if I hold a stick in my hand and use it to move a stone. According to Aquinas, my hand, the stick, and the stone all move at the same time. He makes this point here using the terminology of “essential” causes that are simultaneous and “accidental” causes that are time-based:


In efficient causes it is impossible to proceed to infinity essentially [i.e., simultaneously]. Thus, there cannot be an infinite number of [simultaneous] causes that are essentially required for a certain effect—for instance, that a stone be moved by a stick, the stick by the hand, and so on to infinity. But it is not impossible to proceed to infinity accidentally [i.e., over time] as regards efficient causes. [Ibid]


Aquinas’s causal proof, then, proceeds like this:


1. Some things exist and their existence is caused.

2. Whatever is caused to exist is caused to exist by something else.

3. An infinite series of simultaneous causes resulting in the existence of a particular thing is impossible.

4. Therefore, there is a first cause of whatever exists.


            Aquinas did not give us an example of the sort of simultaneous causes in the natural world that traces immediately back to God, but here is a likely instance of what he is talking about. Consider the motion of the winds. At the very moment that the winds are moving, there are larger physical forces at work that create this motion. In medieval science, the motion of the moon is responsible for the motion of the winds. But the moon itself moves because it too is being simultaneously moved by other celestial motions, such as the planets, the sun, and the stars. According to Aquinas, simultaneous causal sequences of motion cannot go on forever, and we must eventually find a first cause of this motion, which “everyone understands to be God.”

            So much for Aquinas’s second way to prove God’s existence. As noted, the first and third ways follow similar strategies, insofar as they claim that causal sequences of change and contingency cannot go on forever. The fourth way is like Anselm’s argument from absolute goodness: there must be an absolute standard of goodness which is the cause of the good that we see in lesser things. His fifth way, though, is unique and is a version of what in later times is called the design argument. He writes,


The fifth way is taken from the governance of the world. We see that things which lack intelligence, such as natural bodies, act for an end, and this is evident from their acting always, or nearly always, in the same way, so as to obtain the best result. Hence it is plain that not fortuitously, but designedly, do they achieve their end. Now whatever lacks intelligence cannot move towards an end, unless it be directed by some being endowed with knowledge and intelligence; as the arrow is shot to its mark by the archer. Therefore some intelligent being exists by whom all natural things are directed to their end; and this being we call God. [ST 1, Q. 2, Art. 3]


More formally, his argument is this:


1. Objects without intelligence act towards some end (for example, a tree grows and reproduces its own kind).

2. Moving towards an end exhibits a natural design that requires intelligence.

3. If a thing is unintelligent, yet acts for some end, then it must be guided to this end by something which is intelligent.

4. Therefore, an intelligent being exists that moves natural things toward their ends, which is God.


The central notion behind this argument is that natural objects such as plants and animals have built-in purposes. Here Aquinas draws directly on Aristotle’s concept of a “natural object” which has an innate impulse towards change in specific ways. According to Aquinas, when natural objects move towards their end, this reveals a natural design that could not have come about through chance, but requires intelligence. Since plants and animals lack intelligence to do this, some other intelligence is responsible for this, namely God.


Divine Simplicity and Religious Language

Not only can we prove the existence of God through reason unaided by faith, but there are some features of God’s existence that reason by itself can also reveal to us. Religious philosophers often describe God as having a cluster of attributes, such as being all-powerful, all-knowing, all-good; Aquinas certainly agrees that God is these things. However, he maintains that God in fact has a single attribute: divine simplicity. Several philosophers prior to Aquinas, including Parmenides and Plotinus, held that God is best described as “the One”, namely, a simple, indivisible entity. Aquinas agrees as we see here:


There is neither composition of quantitative parts in God, since He is not a body; nor composition of matter and form; nor does His nature differ from His person; nor His essence from His existence; neither is there in Him composition of genus and difference, nor of subject and accident. Therefore, it is clear that God is nowise composite, but is altogether simple. [ST 1, Q 3, Art. 7]


According to Aquinas, God has no parts whatsoever, no physical parts, and, more importantly, no conceptual parts, such as specific properties or predicates. His basic proof for God’s simplicity is this:


1. If something is composed of parts then it must be potentially divisible (e.g., an actual book is potentially a pile of torn out sheets of paper).

2. God is not potentially divisible.

3. Therefore God is not composed of parts (i.e., God is simple).


While God in is true nature is simple, Aquinas concedes that to finite human minds he appears to have distinct parts. The reason is that our minds are designed to understand things in the world around us, virtually all of which have parts--parts of trees, parts of chairs, parts of languages. When we then attempt to understand God in his simplicity, we then very naturally view him as a thing that is composed of parts, and attempt to understand him one element at a time. He writes,


We can speak of simple things only as though they were like the composite things from which we derive our knowledge. Therefore in speaking of God, we use concrete nouns to signify His subsistence, because with us only those things subsist which are composite; and we use abstract nouns to signify His simplicity. In saying therefore that Godhead, or life, or the like are in God, we indicate the composite way in which our intellect understands, but not that there is any composition in God. [ST 1, Q 3, Art. 3]


To satisfy our tendency to view God as a composite thing, we can deduce some sub-attributes of God from his main attribute of simplicity. For example, we can say that God is eternal since if a thing is simple, then it has no “before” or “after” and thus is eternal. Similarly, we can say that God is perfect since if a thing is simple then it is completely actualized, with no remaining potentiality, and complete actualization is perfection.

            The whole issue of God’s attributes raises an even more fundamental question of the adequacy of religious language: can any of our descriptions of God satisfactorily represent him? For example, if we say that “God loves us,” what sort of “love” are we talking about, and is the notion of divine love something that can even be put into words? We’ve already seen a variety of answers to this question of religious language: Pseudo-Dionysius said we can only describe God negatively; Maimonides said that we can only describe God allegorically. Aquinas approaches the issue by noting three ways that our words might, at least in theory, apply to God. The first is univocal: the religious and non-religious uses of a word like “love” are completely the same, whether we’re talking about human love or divine love. Aquinas rejects this approach:


Univocal predication is impossible between God and creatures… [The] term “wise” is not applied in the same way to God and to man. The same rule applies to other terms. Hence no name is predicated univocally of God and of creatures. [ST 1, Q. 13, Art. 5]


The problem with the univocal approach is that the gulf between God’s nature and human nature is so vast that the term “love” cannot possibly mean the exact same thing when we’re talking about divine love vs. human love. The next way is equivocal: the religious and non-religious uses of a word like “love” are completely different. Aquinas rejects this approach as well:


Neither, on the other hand, are names applied to God and creatures in a purely equivocal sense, as some have said. Because if that were so, it follows that from creatures nothing could be known or demonstrated about God at all. [Ibid]


The problem here is that if religious language and human language have nothing in common, then we can say nothing at all about God. Rejecting both the univocal and equivocal approach, Aquinas recommends a middle ground between the two: an analogical approach whereby the religious use of a word has some analogy to the non-religious use. For example, we can say that divine love is to God just as parental love is to a parent. He writes,


In analogies the idea is not, as it is in univocals, one and the same, yet it is not totally diverse as in equivocals. Rather a term which is thus used in a multiple sense signifies various proportions to some one thing. Thus “healthy” applied to urine signifies the sign of animal health, and applied to medicine signifies the cause of the same health. [Ibid]


The point is that there is something in common to both religious language and human language, but it can only be understood as a comparison of two relations. For example, to grasp the notion of divine love, we must first examine the relation between human parents and parental love: we have a special attachment to our offspring that overrides every other human interest. In some parallel way, this is what God’s love towards humans involves.


Morality and Natural Law

In the arena of moral philosophy, Aquinas developed a view called natural law theory, which for centuries was one of the dominant views regarding the source of moral principles. In a nutshell, natural law theory holds that God endorses specific moral standards and fixes them in human nature, which we discover through rational intuition. According to Aquinas, there are four kinds of law: eternal law, natural law, human law and divine law. Eternal law, the broadest type of law, is the unchanging divine governance over the universe. This includes both the general moral rules of conduct, such as “stealing is wrong,” and particular rules such as “people should not intentionally write bad checks.” Natural law is a subset of eternal law, which God implants in human nature and we discover through reflection. However, it includes only general rules of conduct, such as “stealing is wrong,” not specific cases. Next, human law is a derivation of natural law that extends to particular cases, such as “people should not write bad checks.” Finally, divine law, as contained in the Bible, is a specially revealed subset of the eternal law that is meant to safeguard against possible errors in our attempts to both obtain natural law through reflection, and derive more particular human laws. In this way we see that the Bible condemns stealing in general, as well as various forms of theft through fraud. All moral laws— whether general ones discovered through reflection, or specific ones derived by legislators, or ones found in the scriptures— are ultimately grounded in an objective, universal, and unchanging eternal law.

            What, specifically, are the principles of natural law that God has embedded into human nature? First, there is one highest principle: “Good is to be done and evil is to be avoided.” Aquinas writes,


This is the first precept of law, that “good is to be done and pursued, and evil is to be avoided.” All other precepts of the natural law are based upon this: so that whatever the practical reason naturally apprehends as man’s good (or evil) belongs to the precepts of the natural law as something to be done or avoided. [ST la-2ae, Q. 94, Art. 2]


From this, we determine what is “good” for us by looking at our human inclinations; he notes six in particular that are connected with our human good: self-preservation, heterosexual activity, educating our offspring, rationality, gaining knowledge of God, and living in society. He writes,


Because in man there is first of all an inclination to good in accordance with the nature which he has in common with all substances: inasmuch as every substance seeks the preservation of its own being, according to its nature: and by reason of this inclination, whatever is a means of preserving human life, and of warding off its obstacles, belongs to the natural law. Secondly, there is in man an inclination to things that pertain to him more specially, according to that nature which he has in common with other animals: and in virtue of this inclination, those things are said to belong to the natural law, “which nature has taught to all animals,” such as sexual intercourse, education of offspring and so forth. Thirdly, there is in man an inclination to good, according to the nature of his reason, which nature is proper to him: thus man has a natural inclination to know the truth about God, and to live in society: and in this respect, whatever pertains to this inclination belongs to the natural law; for instance, to shun ignorance, to avoid harming or offending those among whom one has to live, and other such things regarding the above inclination. [Ibid]


For Aquinas, these six inclinations comprise what is most proper for humans, and provide the basis for the primary precepts of morality. This gives us six primary principles of natural law: (1) preserve human life, (2) have heterosexual intercourse, (3) educate your children, (4) shun ignorance, (5) worship God, and (6) avoid harming others.

            Each of these primary principles encompasses more specific or secondary principles. For example, the primary principle “avoid harming others” implies the secondary principles “don’t steal” and “don’t assault.” These, in turn, imply even more specific or tertiary principles, such as “don’t write bad checks.” As the principles become more specific, they leave the domain of natural law and enter that of human law. When considering whether natural law is the same in all people, he argues that the primary principles are common to everyone, such as “do not harm others.” However, more particular tertiary derivations of human law are not necessarily common to all societies. Still, he argues, human law will carry the force of natural law if the tertiary principles are derived correctly. But, “if in any point it deflects from the law of nature, it is no longer a law but a perversion of law” (ibid, 95).




Since around 1100, scholasticism dominated medieval philosophy with its technical style and efforts to defend theology with philosophy. As Aquinas put it, philosophy is the handmaid of theology. Some philosophers made outright assaults against scholasticism on the grounds that it produced useless quarrels and elevated rationalistic philosophy above true faith. But such outright attacks did little to slow down the momentum that scholasticism had built up over the centuries. Other philosophers, though, writing within the scholastic tradition itself, helped drive a wedge between philosophy and theology, thus helping to bring an end to scholasticism’s dominance. Two of these are John Duns Scotus and William of Ockham.


Scotus: Divine Illumination, Form-Matter, Divine Command Ethics

John Duns Scotus (1266-1308) criticized the longstanding theory of divine illumination, and held that God has the power to change moral principles. Born in Scotland, he joined the Franciscan monastic order at an early age and moved on to study theology at Oxford University. When subsequently teaching at the University of Paris, he was caught in a feud between the Pope and France’s king and temporarily exiled from the country. He died in Cologne, Germany, when, according to rumor, he was buried alive after falling into a coma. In modern editions, Scotus’s writings occupy 25 volumes, most of which he composed during a ten-year period of his life. His reputation for scholarship earned him the nickname “the subtle doctor.” Nevertheless, some years after his death when his views fell into disfavor, his very name “Duns” became synonymous with foolishness, and is thus the origin of our word “dunce.”

            While Scotus wrote on a wide range of philosophical subjects, we will look at his contributions in three areas. First is Scotus’s rejection of divine illumination. We’ve seen that Augustine proposed the idea that God illuminates our minds to enable us to see special truths: “The mind needs to be enlightened by light from outside itself, so that it can participate in truth, because it is not itself the nature of truth. You will light my lamp, Lord” (Augustine, Confessions, 4:15:25). Divine illumination was a popular view of knowledge throughout the middle ages, and by the time of Scotus several philosophers developed it into an elaborate theory. Scotus, on the contrary, argued that human reason can attain certainty on its own, with no assistance from God through divine illumination. The problem with divine illumination is this: if our natural capacity for knowledge is limited, as Augustine and others maintained, then divine illumination cannot help, since it too will be subject to uncertainty. Scotus writes,


When one of those [elements of knowledge] that come together is incompatible with certainty, then certainty cannot be achieved. For just as from one premise that is necessary and one that is contingent nothing follows but a contingent conclusion, so from something certain and something uncertain, coming together in some cognition, no cognition that is certain follows. [Ordinatio n.221]


According to the analogy in the above quotation, an argument is only as strong as its weakest premise: if you have five premises that are certain, yet only one that is uncertain, the entire argument becomes uncertain. For Scotus, the types of certainty that we can attain in our current human condition, without the help of divine illumination, are certainty about logical inference, causal inference, acts we perform, present sense experience.

            A second area of importance in Scotus’s philosophy is his view regarding matter and form. Recall the debate between Plato and Aristotle on the relation between matter and form. Plato held that form can exist independently of material things, such as the forms of justice, 1+1=2, and chairness, all of which exist in the non-physical realm of the forms. Aristotle, on the other hand, held that form cannot exist separately from matter, but, instead, forms must be imbedded into material things, such as the form and shape that an existing wooden chair has. Most medieval philosophers followed Aristotle’s view, which is called hylomorphism (Greek for “material form”). Scotus for the most part accepts Aristotle’s view: the things that we see around us are a mixture of matter and form. However, Scotus makes two important concessions to Platonism. First, he argues that some matter exists without form—a formless substance called “prime matter”. Second, he argues that pure forms can exist that contain no matter—an immaterial form called “substantial form”. Spirits, he argued, are just such substantial forms.

            The third of Scotus’s major contributions to philosophy is his view that God creates morality—a position now called divine command theory. The larger question here is what is the ultimate source of morality? Plato and his followers argued that moral standards like justice, charity, and goodness are eternal and unchanging principles that exist in a non-physical realm. They were not created by God, and, on the contrary, they are so permanently fixed in the cosmic nature of things that God himself cannot even alter them. In this way, moral standards are much like mathematical principles, which are also eternal and unchanging. Scotus denies that moral standards are like this. He writes, “The divine will is the cause of good, and so a thing is good precisely in virtue of the fact that he wills it” (Additiones Magnae 1.48). Similarly he states “Everything other than God is good because it is willed by God, and not vice versa” (Ordinatio, 3.19).

            While this might at first seem to be a good position for a religious believer to hold, it has an unpleasant side effect, which Scotus himself recognized: God can create any moral values he wants, and he can change them any time he wants. In fact, he maintains, the Bible itself contains a record of God revoking previously established moral principles for special purposes. Specifically, God commanded Abraham to kill his son as a sacrifice; he commanded the Israelites to steal household goods from their Egyptian neighbors; he commanded the prophet Hosea to have children with a prostitute. As unsettling as this might be, according to Scotus we must simply recognize that God has this kind of authority over the creation and suspension of moral principles. Scotus adds, though, that some moral standards even God cannot change, specifically the first few of the Ten Commandments which tell us to avoid making idols and using God’s name in vain. The reason that these are unchangeable, according to Scotus, is that part of God’s nature is that he should be loved: “It follows necessarily that if he is God, he should be loved as God, and that nothing else is to be honored as God, nor is irreverence to be committed toward God” (Oxford Commentary, 3:37).


Ockham: The Razor and Nominalism

William of Ockham (1285-1347) formulated the principle of simplicity known as “Ockham’s Razor” and is also remembered for his view that universals are only concepts in people’s minds. Born near London, Ockham joined the Franciscan monastic order at an early age. As he produced one philosophical work after another, some of his more controversial views attracted the attention of the Pope, and he was investigated for heresy. He further irritated the Pope by holding that Jesus and his apostles owned no property—a view that was especially inflammatory at a time when Popes lived like wealthy kings. He was excommunicated from the Church and, fleeing for his life, he went into exile where he continued writing until he died.

            Like Scotus, Ockham challenged many assumptions held by previous philosophers in the scholastic tradition. For starters, in the important issue of faith and reason, he held that belief in God is a matter of faith rather than knowledge. Theology is not a science since we have no direct knowledge of God. He writes,


In order to demonstrate the statement of faith that we formulate about God, what we would need for the central concept is a simple cognition of the divine nature in itself—what someone who sees God has. Nevertheless, we cannot have this kind of cognition in our present state. [Quodlibetal Questions, pp. 103-4]


Further, he argues, proofs for God’s existence fail, and the notion of the Christian trinity is logically contradictory. Knowledge of God is based only on faith, and the truths God has chosen to reveal to us. In this way, Ockham holds a faith-only approach to religious knowledge, similar to that of Tertullian.

            Ockham is most famous for his principle of simplicity, popularly called “Ockham’s Razor,” which states that entities should not be multiplied needlessly and that the simplest of two competing theories is to be preferred. Suppose, for example, that I see leaves moving around outside. One explanation for this is that invisible demons are grabbing hold of them and stirring them around. An alternative explanation is that the wind is blowing them. According to Ockham’s Razor, I should reject the first theory since it unnecessarily postulates the existence of a supernatural entity (invisible demons) when I can explain the phenomenon perfectly well with ordinary natural events (the wind). Philosophers prior to Ockham routinely used this notion in the course of proving one thing or another. Ockham, though, relied on it regularly, thus making it something like a trademark for him.

            One important application of his Razor is with the medieval problem of universals. Recall what the three options are for universals as developed by Boethius. First, there’s Plato’s view that universals exist in the realm of the forms, separate from physical bodies. Second, there is Aristotle’s view that universals are built into physical things. Third, there is the view that universals are merely mental abstractions that do not exist in the external world. Applying Ockham’s Razor to this issue, we need only ask which of these three views is the simplest and multiplies the fewest number of entities? Plato’s view clearly has lots of excess baggage; indeed, Plato postulates an entire nonphysical realm of the Forms to house universals. Aristotle’s theory also has excess baggage. In addition to saying “the ball is red” we must also say that the universal “redness” is embedded in the ball. The simplest theory, then, is the third which holds that universals exist only as concepts in our minds. Ockham writes,


Nothing should be posited as naturally necessarily required for some effect unless certain experience or a certain argument from what is self-evident leads to that; but neither of these leads to the positing of a universal species. [Commentary on the Sentences, Bk. 2, Q. 15]


This third view of universals, which Ockham endorses, is sometimes called conceptualism, emphasizing the role of mental concepts, but more often it is called nominalism (or “name-ism”) emphasizing the human tendency to name abstract mental concepts such as “redness”.

            Ockham offered several arguments in defense of nominalism, with simplicity being just one. Briefly, here are two others. First is the argument from individual existence. According to Ockham, everything that exist should be logically independent from everything else. Plato’s and Aristotle’s views of universals undermine this since it connects objects together through universals. Second is the argument from God’s sovereignty: universals limits God’s power. God should be able to create or destroy things as he chooses. Suppose that universals existed outside the mind as Plato or Aristotle suggested, and that the universal of redness, for example, was connected with all particular red things. If God then chose to destroy a red ball, he would thus also destroy the universal “redness” and every other red thing that’s connected with it. Ockham writes,


God would not be able to annihilate one individual substance without destroying the other individuals of the same kind … [since] he would destroy the universal that is in it and in others of the same essence. [Summa Totius Logica, 1:15:5]


            A final influential component of Ockham’s philosophy is his extreme view of the divine command theory. Earlier we discussed Scotus’s view of God’s ability to create moral standards, particularly ones involving murder, theft and sexual morality. God can mandate or suspend these as he sees fit. But Scotus adds that other moral standards, such as duties to love God, are fixed within the nature of God himself and cannot be changed. Ockham, however, takes the more radical position that God can create and alter both types of moral principles if that’s what he chose. Specifically, God could command us to hate him and, thus, that would be the morally right thing to do. He writes,


Every will can conform to the commands of God. God can, however, command a created will to hate Him. Therefore, the created will can do this. Moreover, any act that can be just on earth could also be just in heaven. On earth the hatred of God can be just, if it is commanded by God himself. Therefore, the hatred of God could also be just in heaven. [Fourth Book of the Sentences, 13]




Considering that Medieval philosophy covers a period of 1,000 years—two-fifths of the entire span of the history of philosophy—it may seem a little odd to devote only one chapter to it as we’ve done here. It is now common practice, though, to deemphasize the Medieval thinkers in deference to those of other historical periods. It is not because of a lack of philosophical writings during this period, since far more Medieval philosophy books survive than do those by ancient Greek writers. The reason is that the entire program of Medieval philosophy rests on a key assumption: readers must be compelled by the specific notion of God that’s advocated by the Jewish, Christian, and Muslim religious traditions. Most of the issues that Medieval philosophers wrestled with focus directly on God—his existence, nature, creative activity, and how he fashioned human nature. While at least some of these issues may be interesting in their own right, Medieval philosophy still mainly addresses an audience of monotheists. Medieval Europe consisted almost exclusively of such believers. But as the world opened during the Renaissance and the centuries following, the audience of philosophically-minded readers greatly expanded. Polytheists, pantheists, and atheists from all corners of the globe have a harder time engaging in that dialogue.

            Nevertheless, even today there remains a large group of philosophically-minded monotheists who connect with the religious assumptions of the Medievals, and continue to look to their writings for inspiration. In that context, the contributions of Medieval philosophers are no less profound and innovative than those of the ancient Greeks. As religious philosophers today continue to explore such issues, they invariably begin with the basic arguments of the Medievals and follow their philosophical methodology. Scholasticism in particular continues to this day through the efforts of Christian philosophers who follow in the tradition set by Aquinas. Within that environment, the program of Medieval philosophy is alive and well.




Plato’s Ethics involves Loving God as the Highest Good (City of God, 8)

            4. Among the disciples of Socrates, Plato was the one who shined with a glory that far exceeded that of the others, and who not unjustly eclipsed them all. . . .

             5. If, then, Plato defined the wise man as one who imitates, knows, loves this God, and who is made blessed through fellowship with Him in His own blessedness, why should we discuss the other philosophers? It is evident that none come nearer to us than the Platonists. . . .

            8. Plato held that the highest good is to live according to virtue, and affirmed that he only can attain to virtue who knows and imitates God, insofar as knowledge and imitation are the only cause of blessedness. Therefore, Plato did not doubt that to philosophize is to love God, whose nature is incorporeal. From this it certainly follows that the student of wisdom, that is, the philosopher, will then become blessed when he begins to enjoy God. For though he is not necessarily blessed who enjoys that which he loves (for many are miserable by loving that which ought not to be loved, and still more miserable when they enjoy it). Nevertheless, no one is blessed who does not enjoy that which he loves. For even they who love things which ought not to be loved do not count themselves blessed by loving merely, but by enjoying them. Who, then, but the most miserable will deny that he is blessed, who enjoys that which he loves, and loves the true and highest good? But the true and highest good, according to Plato, is God, and therefore he would call him a philosopher who loves God. For philosophy is directed to the obtaining of the blessed life, and he who loves God is blessed in the enjoyment of God.


Plato Comes the Closest to Christianity (City of God, 8)

            9. Concerning the supreme God, these [Platonist] philosophers held that He is both the maker of all created things, the light by which things are known, and the good in reference to which things are to be done. They held that we have in Him the first principle of nature, the truth of doctrine, and the happiness of life. Whether these philosophers may be more suitably called Platonists, or whether they may give some other name to their sect . . . we prefer these to all other philosophers, and admit that they come nearest to us. . . .

             11. Certain participants with us in the grace of Christ are surprised when they hear and read that Plato had notions concerning God which they recognize have considerable agreement with the truth of our religion. Some have concluded from this that, when Plato went to Egypt, he had heard the prophet Jeremiah, or, when travelling in the same country, had read the prophetic scriptures, which opinion I myself have expressed in certain of my writings.


Glimpsing Eternal Forms through the Mind’s Eye (On the Trinity 12.14)

Few can see the Eternal Forms with the mind’s eye. When we see them as much as they can be seen, we do not retain them, but are repelled by the retraction of the mind’s eye itself. Thus, we have a temporary glimpse of a thing that is eternal. Yet we commit this temporary glimpse to memory through the instructions by which our minds are taught. Thus, the mind that is forced to pass from it may be able to return to it again. But if the thought should not return to the memory and find there what it had committed to it, the mind would nevertheless be led to it. This is just as an uninstructed person, who had been led before to something, would find it where he had first found it. . . . Through recollection, the mind will then be able to reflect upon it, to at least some extent, and then transfer what it has learned into a more systematic knowledge. But if our memory of it has been blotted out by complete forgetfulness, once again, under the guidance of teaching, we will come to that which had altogether fell away, and we will find it just as it was.


Divine Illumination of the Eternal Forms that Exist in God’s Mind (83 Questions, 46)

Where are we to believe that these Eternal Truths [by which God created all things] exist, if not in the very mind of the Creator himself? Indeed, he saw nothing outside of him that could serve him as a model for what he wanted, and it would be sacrilegious to assume that he could. Suppose that these Eternal Truths of all things (whether created or yet to be created) are contained in the divine mind. Suppose also that there can be nothing in the divine mind that is not eternal and immutable. Suppose finally that it is these Eternal Truths of things that Plato calls “Forms”. It thus follows that not only do Eternal Forms exist, but that they are true because they are eternal, permanent in their form, and immutable. It is by participation in them that everything exists, in whatever way it exists. Now, the rational soul exists in all creatures, and it is close to God when it is pure. In the proportion in which it is united to Him by charity, it finds itself filled and illuminated by that intelligible light, by means of which it sees. It is not by the eyes of the body, but by that which is best in itself that it sees, namely, by its intelligence. When contemplating these reasons she enjoys great happiness. Moreover, as we have said, we call these Eternal Truths ideas, or Forms, or species, or reasons. People may name it as they choose, but it is only very few who can see the truth.




Introduction: One of the main issues for philosophers during the Middle Ages the relation between faith and reason. Thomas Aquinas argued that reason can go a long way in establishing religious truths, such as the existence and nature of God, but faith in divine revelation still is required for establishing the more particular truths of Christianity. In this selection, Aquinas explains the dual paths toward knowledge of God, the need for faith in addition to reason, and the compatibility of faith and reason.


Two Types of Truths about God

3. The truths that we confess concerning God fall under two categories. [First] some things that are true of God are beyond all the competence of human reason, such as that God is three and one. There are other things to which even human reason can attain, such as the existence and unity of God, which philosophers have proved to a demonstration under the guidance of the light of natural reason. It is clear that there are points of absolute intelligibility in God that are altogether beyond the compass of human reason. . . . Human understanding cannot go so far with its natural power as to grasp God’s substance, since, under the conditions of the present life, knowledge and understanding begin with the senses. Therefore, objects beyond the senses cannot be grasped by human understanding except so far as knowledge is gathered of them through the senses. But things of sense cannot lead our understanding to discover in them the essence of the divine substance, since they are effects inadequate to the power that caused them. Nevertheless [as to the second category] our understanding is thereby led to some knowledge of God, namely, of his existence and of other attributes that must necessarily be attributed to the first cause. There are, therefore, some points of intelligibility in God, accessible to human reason, and other points that altogether transcend the power of human reason. The same thing may be understood from consideration of degrees of intelligibility. Of two minds, one of which has a sharper insight into truth than the other, the higher mind understands much that the other cannot grasp at all. . . . Hence not all things that God understands in Himself can be grasped by the natural knowledge of an angel; nor is human reason competent to take in all that an angel understands of his own natural ability. . . .


Three Disadvantages of Truths Gained Solely through Reason

4. If a truth of this nature were left to the sole inquiry of reason, three disadvantages would follow. One is that the knowledge of God would be confined to few. The discovery of truth is the fruit of studious inquiry, and very many people are hindered from this. . . . It is only with great labor of study that it is possible to search out and arrive at these truths, and only a view are willing to undertake this labor for sheer love of knowledge. Another disadvantage is that those who did arrive at the knowledge or discovery of the aforesaid truth would take a long time to gain it, because of the profundity of such truth and the many prerequisites to the study. In youth and early manhood, the soul is tossed back and forth on the waves of passion and is not fit for the study of such high truth. It is only in settled age that the soul will become prudent and scientific, as the Philosopher [Aristotle] says. Thus, if the only way open to the knowledge of God were the way of reason, the human race would dwell long in thick darkness of ignorance. Thus, the knowledge of God, which is the best instrument for making people perfect and good, would come only to a few, and to those few after a considerable lapse of time. A third disadvantage is that, because of the infirmity of our judgment and the disquieting force of imagination, there is some mixture of error in most of the investigations of human reason. This would be a reason for many to continue doubting even the most accurate demonstrations, since they would not perceive the force of the demonstration, and they would also see that different judgements by different people who have the reputation of being wise. Besides, along with much demonstrated truth there is sometimes an element of error. This error, though not technically demonstrated, is nevertheless asserted on the strength of some plausible and sophistic reasoning that is taken for a demonstration. Therefore, it was necessary for the real truth concerning divine things to be presented to men with fixed certainty by way of faith. Therefore, there is a practical arrangement to divine mercy, whereby things even that reason can investigate are commanded to be held on faith, so that everyone might easily access the knowledge of God, and do so without doubt and error. . . .


The Truth of Reason is not Contrary to the Truth of Christian Faith

7. The natural dictates of reason must certainly be quite true, for it is impossible to think of their being otherwise. Nor again is it permissible to believe that the tenets of faith are false, being so evidently confirmed by God. Since therefore falsehood alone is contrary to truth, it is impossible for the truth of faith to be contrary to principles known by natural reason. Whatever is put into the disciple’s mind by the teacher is contained in the knowledge of the teacher, unless the teacher is teaching dishonestly, which would be a wicked thing to say about God. But the knowledge of principles naturally known is put into us by God, since God himself is the author of our nature. Therefore these principles also are contained in the divine wisdom. Whatever therefore is contrary to these principles is contrary to divine wisdom, and cannot be of God.


Source: Thomas Aquinas, Summa Contra Gentiles, Book 1, chs. 3, 4, 7, tr. Joseph Ricaby (adapted).




Please answer all of the following questions.


1. Explain the four main issues for medieval philosophers?

2. Explain Augustine’s views on faith, the four areas of genuine knowledge, divine illumination, and time.

3. Explain Augustine’s three solutions to the problem of evil, and his view of free will and divine foreknowledge.

4. Explain Augustine’s view of appropriate desire, and his distinction between the earthly and heavenly cities.

5. Explain Pseudo-Dionysius’s three positive assertions about God and three negative denials about God.

6. Explain Boethius’s notion of the three ways of understanding universals, and his solution to the problem of free will and divine foreknowledge.

7. Explain Anselm’s proof for God from absolute goodness, his ontological argument, and Gaunilo’s criticism of it.

8. Explain Averroes’ view of the two kinds of scriptural meaning, the three types of people who attempt to understand scripture, and the double truth doctrine of his followers.

9. Explain Maimonides’s views on religious language, the issue of whether God has a body, and statements about God’s mercy and anger.

10. Explain Aquinas’s views on the relation between faith and reason, and the twofold truth.

11. Explain Aquinas’s distinction between an accidental cause and an essential cause, and how this distinction applies to his second way of proving God’s existence.

12. Explain Aquinas’s view of divine simplicity, and the three ways of using religious language.

13. Explain Aquinas’s view of the four kinds a law, and his distinction between the highest, the primary and the secondary principles of natural law.

14. Explain Scotus’s criticism of divine illumination, his distinction between matter and form, and his divine command theory.

15. Explain Ockham’s views on faith and reason, the razor, nominalism, and extreme divine command theory.

[Reading 1: Augustine on Plato, the Forms and Divine Illumination]

16. Explain Augustine’s view on the compatibility between Plato’s philosophy and Christianity.

17. Explain Augustine’s view on how we glimpse eternal forms through the mind’s eye.

18. Explain Augustine’s view on divine illumination of the eternal forms in God’s mind

[Reading 2: Aquinas on Faith and Reason]

19. Explain Aquinas’s view of the two types of truth about God.

20. Explain Aquinas’s view of the three disadvantages of truths gained solely through reason.

 [Questions for Analysis]

21. Pick any one of the following views by a Medieval Philosopher and criticize it in a minimum of 150 words. Augustine: skepticism; divine illumination; time; free will and divine foreknowledge; earthly and heavenly cities. Pseudo-Dionysius: positive and negative assertions about God; Boethius: free will and divine foreknowledge. Anselm: proof for God from absolute goodness; the ontological argument. Averroes: types of scriptural meaning; three types of scripture readers; double truth doctrine. Aquinas: twofold truth; five ways; divine simplicity; three uses of religious language; natural law. Scotus: divine illumination; divine command theory. Ockham: faith and reason; extreme divine command theory.