Throughout his ethical writings, Thomas Aquinas frequently uses logical terms such as "propositio," "conclusio," "syllogismo," "deductum," and "demonstratum."⁽¹⁾ This is particularly so in his "Treatise on Law" (S.T. 1a2ae Q. 90-108).⁽²⁾ Recently, many commentators have argued that Thomas's use of such terms is metaphorical. For example, R.A. Armstrong writes,
 

...when we speak of a precept "following" or being "derived" from another, we are not suggesting a procedure in any way analogous to the strict deductive system employed by Euclid.⁽³⁾

Against commentators such as Armstrong, I will argue that the "logic" referred to by Thomas in his account of natural law is best interpreted as formal, syllogistic logic.⁽⁴⁾ What emerges is a more precise account of how actions are related to natural law, and a procedure which takes much of the guess work out of discovering our moral duty.

I will argue that natural law, for Thomas, involves a chain of logical syllogisms, beginning with a highest moral principle, followed by more specific moral principles, and finally ending with a practical syllogism, the conclusion of which is an action. What is at stake here is the success of natural law itself. For, unless we have a clear account of how these principles can be deduced one from another, then natural law will have little relevance in guiding our particular actions.⁽⁵⁾ In developing my interpretation, I first attack the popular view that Thomas's highest moral principle, that "good ought to be done and evil avoided," is analytic. Second, I argue that the most fair reading of the "Treatise on Law" suggests a strict logical relation between the highest moral principle and the more subordinate ones. Finally, I argue that the practical syllogism also involves a logical deduction, where the minor premise is a propositional attitude of perception, and the conclusion is an action which indicates a proposition. I begin with a brief account of natural law.
 
 

Thomas develops the idea of natural law most fully in his "Treatise on Law." He begins noting that law in general is a rational dictate aimed at the common good. There are four kinds of law: eternal law, natural law, human law and divine law. Eternal law, tracing back to Augustine,⁽⁶⁾ is the unchanging divine governance over the universe. This covers both the general rules and particular cases. Natural law is a subset of eternal law which is obtainable by humans, but covers only general rules. Human law is an interpolation of natural law which is extended to particular cases. Finally, divine law (contained in the Bible) is a specially revealed portion of the eternal law which is meant to check possible errors in particular human laws.

Question 94 of the "Treatise on Law" directly addresses the concept of natural law in six articles. First, Thomas argues that our knowledge of the natural law is supplied by a habit of practical reason called "synderesis." Second, the natural law contains one key precept, from which subordinate precepts flow. Third, all virtuous acts in general are prescribed by the natural law, although their particular instances are not. Fourth, the most primary precepts of natural law are the same in all men, although the more particular secondary precepts are not (e.g. regarding theft). Fifth, the primary precepts of natural law cannot change, although the secondary derivations can change. Finally, humans cannot lose their knowledge of the primary precepts of natural law, although they can of the secondary ones.

In short, there is a hierarchical chain of principles involved in natural law, with the highest principle being its purest expression, and derived principles successively losing sanction. Throughout the "Treatise on Law," we find four tiers of these moral principles: the highest principle, primary principles, secondary principles of human law, and, finally, laws of nations.
 
 

As noted above, our knowledge of all natural law arises from synderesis, which is an inborn habit of our practical reason. Thomas explains this habit in three key places:
 

...the principles our nature imparts to us in practical matters do not belong to a special power but to a special habit there by nature, synderesis. And thus synderesis is said to incite us to good and to deter us from evil in that through first principles we both begin investigation and judge what we find. (1a Q. 79, 12)
 
Synderesis is called the law of our understanding inasmuch as it is the habit of keeping the precepts of natural law, which are the first principles of human activity. (Q. 94, 1)
 
Natural reason determines beforehand the ends of moral virtue by what is called synderesis.... (2a2ae, Q. 47, 6)

The importance of synderesis is that all other moral principles are referred back (referuntur) to, and have a single root (una radice) in this most pure intuition (Q. 94, 2). Accordingly, the highest moral precept is often referred to by commentators as the synderesis principle. The content of the synderesis principle described in the following:
 

...every agent acts on account of an end, and to be an end carries the meaning of to be good. Consequently the first principle for the practical reason is based on the meaning of good, namely that it is what all things seek after. And so this is the first command of law, 'that good is to be sought and done, evil to be avoided'; all other commands of natural law are based on this.... As converging on one common primary precept these various precepts of natural law all take on the nature of one natural law. (Q. 94, 2)

The synderesis principle, then, is that "good is to be sought and done, and evil to be avoided." Two aspects of the above quote deserve attention. First, the meaning Thomas assigns to "good" is that which all things seek after. More specifically, what is sought after is a proper human end:
 

...the good or evil of an action, as of other things, depends on its fullness of being or its lack of that fullness. Now the first thing that belongs to the fullness of being seems to be that which gives a thing its species. (Q. 18, 2)⁽⁷⁾

The second important feature of the synderesis principle is that it contains two distinct parts:
 

(1) If X is for a proper human end, then X ought to be done.

(2) If X is not for a proper human end, then X ought not to be done.
 

(2') If X ought to be done, then X is for proper human ends.

Several commentators, such as Armstrong, Copleston, D'Arcy and O'Connor, have attacked the synderesis principle as being a vacuous tautology, "whose truth depends on the meaning of the terms used in expressing them."⁽⁹⁾ D'Arcy, for example, believes this principle is analytically true. And, since tautologies say nothing about the facts involved in practical reasoning, the synderesis principle cannot serve as a major premise in practical reasoning. The function of the synderesis principle, according to D'Arcy, is that it is a purely formal principle "providing the rule that governs all moral reasoning, rather than its universal premise."⁽¹⁰⁾

Thomas does say that the synderesis principle "is based on the meaning of good" (Q. 94, 2). Initially this appears to support D'Arcy's interpretation. However, Thomas is only stressing his technical use of the word "good," as he intends it to mean for a proper end. This does not reduce the synderesis principle itself to a tautology. Consider the pursue virtue clause of the synderesis principle: "good ought to be done." This clause is tautological if and only if the definition of "good" includes "ought," or an obligation for action. But, nothing indicates that Thomas believes obligation is included in the concept of for a proper end.⁽¹¹⁾ Further, it is not unorthodox to give "good" and "ought" different meanings as, I suggest, is the case here. Hare and Mackie, for example, make strong distinctions between these two meanings.⁽¹²⁾ Thus, the synderesis principle is not a tautology, as D'Arcy believes.

Armstrong argues similarly that "no person who used language in the normal way could say on the one hand 'X is good' but on the other 'you ought not do X'.... This principle, 'good ought to be done and evil ought to be avoided,' rather than being the first principle from which all others are derived [has] the status of being enshrined in all other natural law principle."⁽¹³⁾ Although there is a slight error in Armstrong's wording of the problem, the gist of his attack is that we cannot say "X is good" yet "X need not be done."⁽¹⁴⁾ But, given Thomas's definition of "good," the contradiction which Armstrong seeks does not arise. For, there is no definitional problem in saying, "X is for a proper human end" yet "you need not do X." Thomas, no doubt, believes this utterance is false. However, it is known to be false only through the synderesis principle. This is precisely why Thomas emphasizes the synderesis principle. Conceivably, a person without the synderesis principle could understand the concept of obligation, yet successfully pursue his end without knowing he was thereby fulfilling his obligation. This might be how Thomas would describe followers of rival moral systems, such as utilitarians. Thus, the job of the synderesis principle is to establish and continually reminds us of the link between human ends and obligation.

Granting that the synderesis principle is not analytic, how meaningful of a principle is it? Vernon J. Bourke argues that the synderesis principle has been misunderstood: "It does not tell man what are the good things that he should do; it is simply an obvious judgment that if you know that something is good for you to do, then you ought to do it."⁽¹⁵⁾ Bourke's rejection of the synderesis principle rests on his interpretation that natural law is not the basis of Thomas's ethics.⁽¹⁶⁾ Nevertheless, if the synderesis principle is only an obvious judgment, as Bourke suggests, it will have little application to moral judgments.

There are two ways that the synderesis principle is meaningful. First, like any first principle of morality, the synderesis principle is important in resolving moral dilemmas between secondary principles. As Mill suggests with his principle of utility, when a dispute arises between two principles (such as not lying and not harming others), we determine what is right according to the greatest happiness produced. With the synderesis principle, the right action would be the one which was most proper for human ends. In this sense, the synderesis principle is as meaningful as Mill's principle of utility.

The synderesis principle is also significant because of its appeal to the human telos, as opposed to utility or universalizability.⁽¹⁷⁾ Accordingly, the more subordinate principles of morality become obligatory by being in accord with our proper end.

Thomas explains the connection between the synderesis principle and the primary precepts of morality in the following:
 

And so this is the first command of law, 'that good is to be sought and done, evil to be avoided'; all other commands of natural law are based on this. Accordingly, then, natural-law commands extend to all doing or avoiding of things recognized by the practical reason of itself as being human goods. (Q. 94, 2)

(1) All things which are for proper human ends are things we ought to do.

(2) All X are things which are for proper human ends.

(3) Therefore, All X are things we ought to do.
 

In any case, several aspects of Thomas's discussion suggest that deductions from the synderesis principle are syllogistic. The first involves the relation between the synderesis principle and the subordinate primary principles. Thomas argues that we discover our telos by considering our most basic human natural inclinations (Q. 94, 2). These he lists according to the three Aristotelian faculties of the human soul. Corresponding to the vegetative faculty, we have an inclination for self-preservation. From our appetitive faculty, we have an inclination toward heterosexual activities, and an inclination to educate our offspring. Finally, according to our rational faculty, we have inclinations to be rational, know God, and live in society. For Thomas, these six inclinations comprise what is most proper for humans, and provide the basis for the primary precepts of morality.

From these natural inclinations, six primary precepts emerge: (1) preserve human life, (2) have heterosexual (as opposed to homosexual) intercourse,⁽¹⁹⁾ (3) educate your children, (4) shun ignorance, (5) worship God, and (6) avoid offending others.⁽²⁰⁾ Thomas notes specifically that the divine law corroborates the last two of these: "thou shalt love the Lord thy God," and "thou shalt love thy neighbor" (Q. 100, 3 and 11).⁽²¹⁾ This procedure of arriving at primary principles through natural inclinations is syllogistic in nature. Natural inclinations are brute facts of human existence. To recognize our moral obligation from these inclinations, there must be logical connection between these, and the fact that obligation is linked to our telos. The following illustrates this logical connection with the primary principle of avoiding harmful acts:
 

1. All things which are unsuitable for human ends are things one ought not do. [vice clause of the synderesis principle]

2. All harmful acts are things which are unsuitable for human ends. [based on the observation that humans instinctively live in society]

3. Therefore, all harmful acts are things one ought not do. [primary principle]
 

(1) All acts which harm others are acts we ought not do. [from a primary principle of natural inclination]

(2) All acts of unjustified killing are acts which harm others.

(3) Therefore, All acts of unjustified killing are acts we ought not do.

The syllogistic structure of practical reasoning can also be seen in Thomas's account of the final tier of principles of human law, which may be called tertiary principles. As with secondary principles of human law, there are two sorts of tertiary principles. First, there are civil laws which are customary, and obtain their authority from the governing institution itself (Q. 95, 4, cf. 100, 11; and 104, 1). Second, there are the laws of nations (jus gentium)⁽²³⁾ which involve strict derivation from secondary principles. To the laws of nations "belong those things which are derived from the law of nature as conclusions from principles, e.g., just buyings and sellings, and the like, without which men cannot live together; and this belongs to the law of nature, since man is by nature a social animal..." (Q. 95, 4). Like the secondary prohibitions against theft, the tertiary prohibitions against fraud are prescribed by statesmen who are experts in matters of law. Again, these tertiary principles carry some force of natural law. The sanction of natural law inevitably becomes diminished as we proceed to more particular principles, since these depend on cultural influences. Plagiarism, for example, might not be considered stealing in some cultures. Nevertheless, the general notion of fraud would still be a species of stealing, and thus violate natural law.

Beginning with the "avoid vice" clause of the synderesis principle, the deduction of primary, secondary, and tertiary principles is as follows:
 

(1) All things which are unsuitable for human ends are things one ought not do. [synderesis principle]

(2) All harmful acts are things which are unsuitable for human ends. [based on the inclination of humans to live in society]

(3) Therefore, all harmful acts are things one ought not do. [primary principle]

(4) All acts of stealing are harmful acts. [carefully reflected observation of wise men]

(5) Therefore, all acts of stealingare things one ought not do. [secondary principle]

(6) All acts of fraud are acts of stealing. [observation by legal experts]

(7) Therefore, All acts of fraud are things one ought not do. [law of nations]

This interpretation casts natural law in a new light. Thomas frequently warns about departing from natural law when devising human law. The above account clearly indicates where departures may take place: by invalid deduction, or by supplying an inappropriate minor premise. Because the AAA-1 syllogistic form used in the above chain is fairly intuitive, departures through invalid deduction are not a major threat. Often it would suffice to note, as Thomas does, that "one must not kill may be derived as a conclusion from the principle that one should do harm to no man." The real problem is in supplying the minor premise in each of these, without which subordinate moral principles cannot be deduced. The task of supplying the proper minor premise is so difficult, Thomas argues, that experts in law are needed for the more precise ones and, further, divine law is supplied to check even their mistakes. Although a strict formulation of the chain of practical reasoning may not always be necessary, it is nevertheless the ideal form of deliberation against which our more informal moral decisions must be weighed. It is also the clearest way of seeing where minor premises are involved. In comparison with interpretations which view the logic of natural law as metaphorical, the above account takes some of the guess work out of practical reasoning.

One final syllogism remains to complete Thomas's syllogistic chain of practical reasoning: the practical syllogism. It is by means of this final syllogism that laws of nations lead immediately to an agent's action.
 
 

Thomas's practical syllogism (syllogismus operativus) has its origin in Aristotle. Although Thomas refers to the practical syllogism several times in his writings,⁽²⁴⁾ his fullest explanation is the following from Q. 76, 1:
 

Reason directs human action with two types of knowledge, general knowledge and knowledge of particulars. In deciding to act, the mind constructs a syllogism the conclusion of which is a judgment or a choice. Actions exist in individual situations. Hence, the conclusion of this practical syllogism is singular. We cannot conclude to a particular application of a general premise unless the situation fits the general definition, e.g. to avoid parricide a man would have to know not only that it was wrong but also that the intended victim [hunc] was his father. Ignorance of either of these truths could be the cause of an act of parricide; one would be ignorance of a general principle by which reason is directed, the other would be ignorance of a particular circumstance.

As with Aristotle, a practical syllogism is the final act of practical reasoning by which we initiate a moral action. It consists of a universal major premise (a moral principle), a particular minor premise (an observation about an agent's situation) and a particular conclusion (an agent's doing a particular action).⁽²⁵⁾

O'Connor construes Thomas's account of the practical syllogism quite generally, as being an outline of the entire process of practical reasoning. For O'Connor, where X is any morally significant action, we reason that,
 

Major premise: X is right (or wrong).

Minor premise: This is a case of X.

Conclusion: This ought to be done (or avoided)

However, in the above quote, Thomas suggests that the practical syllogism's function in practical reasoning is more restricted: "...to avoid parricide a man would have to know not only that it was wrong but also that the intended victim was his father." Or,
 

Major premise: It is wrong to kill one's father.

Minor premise: This intended victim of killing is the agent's father.

Conclusion: The agent is restrained from an act of parricide.
 

The standard interpretation of both Aristotle and Thomas is that the practical syllogism only superficially resembles a logical syllogism. Thomas Gilby, for example, argues that Thomas's practical syllogism does not follow strict syllogistic rules:
 

..."syllogism" here does not mean the demonstrative or apodictic syllogism ... but a syllogism according to Aristotle's general definition of an argument where, given a certain thing, something further is bound to follow.

Gilby argues that a practical syllogism differs from more demonstrative syllogisms (such as scientific ones) in that moral decisions are subjective. This subjectivity arises from the fact that (a) information pertaining to the minor premise is "played on by the appetite," and (b) more information is continually being gathered which "cannot be comprehended in the premises."⁽²⁷⁾ But Gilby has not made his point, even when granting the subjective nature of the minor premise in a practical syllogism. He seems to be making a basic confusion between the validity of an argument's form and our knowledge of the truth of an argument's premises. Whereas the subjective nature of the minor premise in a practical syllogism may distinguish it from premises in scientific syllogisms (which are more absolute), this has no bearing on whether formal syllogistic rules are used in practical syllogisms.

More serious arguments against the logical nature of practical syllogisms arise from discussions of Aristotle's practical syllogism, but apply equally to Thomas's account. There are two main objections, one arising from the fact that the minor premise is a perception, and not a proposition, and the other arising from the fact that the conclusion is an action, and not a proposition. The general criticism in both cases is that logical arguments can contain only propositions, and not things like perceptions or actions. I will argue that both of these objections are surmountable for Thomas.

John Cooper has most recently advanced the first objection against Aristotle's formulation of the practical syllogism. According to Cooper,
 

... the minor premise is provided by an act of perception.... Now it is this connection with perception that makes one doubt whether this so-called [practical] syllogism is a syllogism--that is, an argument--at all.⁽²⁸⁾

Cooper argues that the act of perception in the minor premise should not be interpreted as providing a piece of information which leads the agent to choose the right action. Instead, Aristotle is describing a psychological link in a chain leading from a decision to act (major premise), to a perception (minor premise) and finally to an action (conclusion). There is, then, no argument involved, but only a psychological chain of events which, when schematized, resembles the structure of a syllogism. Cooper's conclusion is that the practical syllogism is not a reasoning process, and should not be considered part of moral deliberation.

The success of Cooper's interpretation hinges on whether the perception in the minor premise provides information to be reasoned about. D.K. Modrak argues that, for Aristotle, such information is provided.⁽²⁹⁾ Modrak bases her argument on the notion of a propositional attitude--the attitude that such and such is the case. Typical propositional attitudes include "believing that...," "desiring that...," "saying that...," "wishing that..." and "fearing that...." According to Modrak, the propositional attitude indicated in the minor premise of the practical syllogism is perceptual--perceiving that such and such is the case.⁽³⁰⁾ For this reason (and contrary to Cooper), the practical syllogism is a genuine argument since each line, including the minor premise, indicates a proposition. Although Modrak's interpretation has been criticized for misrepresenting Aristotle's intentions,⁽³¹⁾ she has, nevertheless, provided an interesting alternative to Cooper's non-propositional interpretation of practical syllogisms.

Which of these two interpretations best represents Thomas's view of practical syllogisms? The illustration with parricide, again, is,
 

Major premise: It is wrong to kill one's father.

Minor premise: This intended victim of killing is the agent's father.

Conclusion: The agent is restrained from an act of parricide.

The ostensive reference "this man" (hunc) in the minor premise suggests that, like Aristotle, the minor premise involves a perception. The question is whether it is only a perception, on Cooper's interpretation, or whether it is a perception of a proposition (a perception that such and such is the case) on Modrak's interpretation. Modrak's interpretation seems favorable for two reasons. First, Thomas's account of practical syllogisms in Q. 76, 1 notes that, "Reason directs human action with two types of knowledge, general knowledge and knowledge of particulars." The general knowledge refers to the major premise, and the particular knowledge refers to the minor premise. What is important is that the minor premise involves an item of knowledge which aids in directing action. Hence, the perception that "This intended victim is my father" in the minor premise provides the agent with some propositional knowledge.

Second, Thomas's account of the practical syllogism clearly involves deliberation, for the agent's final decision for restraint arises from his knowledge of the major and minor premise. By contrast, on Cooper's psychological interpretation of the practical syllogism, the final decision for restraint would culminate in the major premise itself. From there on, there is no deliberation--only the movement of psycho-physiological cogs.⁽³²⁾ Thus, a propositional interpretation of the minor premise is to be preferred over a non-propositional interpretation. So far, the practical syllogism should be construed as follows:
 

(1) Major premise: All acts of killing one's father are things one ought not do. [law of nations]

(2) Minor premise: This intended victim of killing is the agent's father. [perception]

(2') Minor premise: Some act of killing this man is (or would be) an act of killing one's father. [proposition indicated by (2)]

(3) Conclusion: The agent is restrained from killing his father. [action]

The second, and most common objection raised against the logical status of practical syllogisms is that its conclusion is an action, as opposed to a proposition. Regarding the conclusions of practical syllogisms, Thomas notes in Q. 76, 1 that "Conferens enim de agendis, utitur quodam syllogismo, cujus conclusio est judicium seu electio vel operatio."⁽³³⁾ There is much flexibility here in the nature of a conclusion to a practical syllogisms. It may be a "judgment (or, in other words, a choice) or an action." Insofar as they are actions, though, the criticism would seem to be appropriate: how can the conclusion to an argument be an action?

One solution to this problem was recently given by Robert Audi. According to Audi, the conclusion of a practical syllogism is a judgment that the agent should do a particular act. This is based on Audi's conviction that the conclusion of a practical syllogism must be an appropriate response to the practical question "what should I do?"⁽³⁴⁾ Clearly, many actions would be appropriate responses to this question. For example, the act of contributing to UNICEF would be an appropriate response to the question, "What should I do about the problem of world hunger?" This approach would seem to cover all morally relevant actions, insofar as they answer the question, "What should I do about such and such?" However, Audi's account tells us only that moral actions involve judgments. He does not show us how moral actions indicate propositions.

A solution may be found in the writings of William Wollaston, the 18th century British rationalist. For Wollaston,
 

Those propositions are true, which express things as they are: or, truth is the conformity of those words or signs, by which things are expressed, to the things themselves.... It is certain there is a meaning in many acts and gestures. Everybody understands weeping, laughing, shrugs, frowns, etc., these are a sort of universal language.

From this, Wollaston concludes that propositions may be indicated by words, signs and actions.⁽³⁵⁾ Wollaston believes that this view of actions-as-propositions is particularly common with morally relevant actions. For example, if I drive away in a particular automobile, I am indicating the proposition that "I have the right to drive away in this vehicle." If I own the automobile, this action indicates a true proposition. If, on the other hand, I am stealing an automobile, then this action indicates a false proposition.

But how, more precisely, would an action indicate a proposition on Wollaston's account? Clearly, Wollaston's theory makes sense only when a particular action is deliberate or intentional. For example, if while sleepwalking I drive away in an automobile, my behavior would not indicate the proposition that "I have the right to drive away in this automobile." Thus, the focus of Wollaston's theory is on my belief states and intentions as they form the foundation of my action, and not, strictly speaking, the physical action itself. Consequently, my physical behavior serves as an indicator of my belief states, and these, in turn, indicate true or false propositions.

This may be what Thomas has in mind when claiming that the conclusion to a practical syllogism may be an action. With the parricide example, the agent's concluding act is one of restraint from killing his father. This indicates the agent's belief state that to kill his father would be wrong, and this, in turn, indicates the proposition that "killing this man is wrong." On this analysis, the practical syllogism about parricide would be as follows:
 

(1) All acts of killing one's father are things one ought not do. [law of nations]

(2) This intended victim of killing is the agent's father. [perception]

(2') Some act of killing this man is (or would be) an act of killing one's father. [proposition indicated by (2)]

(3) The agent is restrained from killing his father. [action which presupposes a belief state]

(3') Some act of killing this man is a thing one ought not do. [proposition indicated by the belief state in (3)]

I have argued that moral reasoning for Thomas involves a chain of logical syllogisms beginning with the synderesis principle, and concluding with an act of a practical syllogism. Particularly, I have shown that the synderesis principle "we ought to do good and avoid evil" is not tautological, and is our ultimate source of knowledge of the natural law. Also, I have argued that subordinate moral principles are syllogistically derived from the synderesis principle, and, to varying degrees, carry the force of natural law. Finally, I have shown that the concluding practical syllogism of this argument chain can be reasonably interpreted as a logical syllogism.

In conclusion, it should be noted how this scheme of practical reasoning affects the individual moral agent. As individuals, we are directly accountable for our most general intuition of natural law through synderesis, and for our final actions determined by practical syllogisms. We are first accountable for understanding our obligation to act in accord with proper human ends, the most clear ends involving honoring God, and living in society. Lawmakers, along with scripture, provide us with particular laws governing of our moral obligation. Although we are bound by these laws, we are not responsible for understanding how these relate to our end. Our final direct responsibility concerns our judgment about whether our actions are in accord with these particular laws. We are responsible for perceiving that an act in question is in accord with tertiary principles and, ultimately, whether the act is in accord with our obligation.

1. All English translations from Summa Theologica are from the Blackfriars edition unless noted otherwise.

2. Hereafter, references to are S.T. 1a2ae unless noted otherwise.

3.R.A. Armstrong, Primary and Secondary Precepts in Thomistic Natural Law Teaching (The Hague, l966), p. l34.

4. This coincides with Robert W. Schmidt's account of logic in Thomas's writings. For Schmidt, Thomistic logic is a methodological science which provides working instruments to other sciences. This includes the speculative sciences of physics, mathematics, and metaphysics, as well as the practical sciences of moral philosophy and art. Schmidt himself does not discuss the precise application of logic to morality. The Domain of Logic according to Saint Thomas Aquinas, (The Hague: Martinus Nijhoff, 1966), pp. 24-31.

5. D.J. O'Connor argues similarly that without such an explanation, "the doctrine of natural law will be no guide to right action. And if this is so, it will have failed as an ethical theory." Aquinas and Natural Law, (London: MacMillan, 1968), p. 73.

6. Augustine, On Free Choice of the Will, I, 6.

7. Translation here by A. Pegis, The Basic Writings of St. Thomas Aquinas, (New York: Random House, l944).

8. Since, for Thomas, humans were not created with a knowledge of eternal law in all its specifics, we therefore have no a priori knowledge of either our specific goods or our specific obligations. However, by experientially reflecting on our apparent goods, we can approximate our true goods and, thus, our true obligations. This runs analogous to how in science our accepted laws of nature approximate the true laws by which nature operates.

9. O'Connor, p. 74. O'Connor and Copleston argue further that there is some confusion or overlap between the synderesis principle and other general primary moral principles. F.C. Copleston, Aquinas, (Baltimore: Penguin Books, 1955), p. 222.

10. Eric D'Arcy, Conscience and Its Right to Freedom (New York, l960), p. 50-52.

11. By "moral obligation" I mean the binding nature of certain principles which is expressed in ethical terms by the subjunctive mood in such expressions as "ought" and "should." The subjunctive mood in Latin often carries the idea of obligation or necessity, especially when coupled with future passive participles and forms of the verb esse, as in the expression "Carthago delegenda sit"--"Carthage ought to be destroyed." "Observantiam" and "obligantur" used by Thomas carry such a meaning. Often, "praecepta" carries the idea of moral obligation and is for this reason sometimes translated "command," "obligation," or "binding." For example, at Q. 98, 5 Thomas argues that the moral precepts of the old law do not get their binding nature by merely being part of the old law, but, rather, by coming under natural law.

12. See R.M. Hare, The Language of Morals, (London: Oxford University Press, 1962), p. 151; J.L. Mackie, Ethics: Inventing Right and Wrong, (New York: Viking Penguin Inc., 1977), pp. 59, 77.

13. Armstrong, p. l8l.

14. Armstrong's criticism is based on the idea that with analytic statements we cannot deny the predicate and affirm the subject without a contradiction arising. Taking the proposition "X is good and X ought to be done," Armstrong negates the second conjunct, "X ought to be done," resulting with, "X ought not to be done." He errs, though, giving narrow scope to this negation rather than wide scope. The negated conjunct should read, "it is not the case that 'X ought to be done.'" Intuitively, the properly negated conjunct says only that "X need not to be done," which is a weaker claim than "X ought not to be done."

15. Vernon J. Bourke, "Is Aquinas a Natural Law Ethicist?," Monist, (1974) Vol. 58, pp. 52-66.

16. Bourke distinguishes between lex naturae and jus naturae in Thomas's writings, both of which translate as "natural law." The former connotes the oral or written law, which is more prominent in Thomas's earlier writings. This is the natural law of the "Treatise on Law." The latter notion is a more fundamental concept of "right reason," and involves rationally perceiving the natural fitness of our actions. This approach, influenced the Aristotle's Ethics, emerges in Thomas's later writings, and dominates the ethics of Summa Theologica (2a 1ae Q. 1-89). See also Bourke's "The Synderesis Rule and Right Reason," Monist (1983), Vol. 66, pp. 71-82. In that work he argues that specific moral principles cannot be derived from the synderesis principle, but are the result of experience.

17. The presence of the human telos is particularly important for MacIntyre who argues that true ethics is not possible without a reference to the proper end of humanity. Whether or not MacIntyre is correct, the synderesis has important cognitive value regarding the human telos.

18. Germain G. Grisez, "The First Principle of Practical Reason," in Aquinas, ed. Anthony Kenny, (New York: Anchor Books, 1969), pp. 340-382.

19. Q. 95, 3, reply 3 notes that a prohibition arising from this inclination is that against homosexual lust.

20. This final precept is also described as "we should do no harm to man" (Q. 95, 2 and 100, 3).

21. In his analysis of the primary moral principles, Armstrong offers a condensed list of four basic principles. The natural human inclinations he focuses on are, (A) self-preservation, (B) sexual union and (C) placement in society. From these he derives the following four primary principles: (l) we ought to respect and preserve not only human life, but where possible all life, (2) the sexual relation requires some form of regulation, (3) the family group ought to comply with some fixed pattern, (4) we ought to live together in obedience to certain rules and regulations (Armstrong, pp. 46-50).

22. Specifically, Thomas states that primary principles are self-evident to human reason. Given his view that primary principles derive from the synderesis principle, this is best interpreted to mean that the inference of primary principles is self-evident. Further, the self-evident inference seems to involve our universal ability to supply the minor premise of that syllogism. Thomas often makes the distinction between things which are self-evident in themselves, and self-evident to us (S.T. 1a 2, l; and 1a2ae 94, 2). Things self-evident in themselves need not be discoverable to the average person upon reflection, but might require a sophisticated demonstration, such as arguments for God's existence. Armstrong argues that certain primary principles are self-evident in themselves, but not to us. I believe this is a mistake. For Thomas, the self-evident deduction of primary principles to all men is never in question. He implies, though, that secondary principles are self-evident in themselves, but not always to us.

23. He also calls these superadded moral principles, or praecepta moralia superaddita (Q. 100, 11).

24. The Commentary on the "Nicomachean Ethics" contains only a general reference to syllogisms, contrasting them to induction (discussed at 1147-1148 in the context of Aristotle's "dry food" syllogism). His Commentary on Aristotle's "De Anima" provides the following unhelpful discussion of the practical syllogism: "We need therefore a measure for our actions, a criterion for discerning what is most worth doing. And this will be the middle term of the syllogism of the practical reasoning issuing in a choice" (New Haven: Yale university Press, 1951), sect. 841.

25. Unlike Thomas, moral reasoning for Aristotle is for the most part not syllogistic. John Cooper writes, "Deliberation as Aristotle represents it does not take a form that remotely resembles an Aristotelian syllogism, and Aristotle never says or implies that it does.... It seems quite clear... that Aristotle only suggests a syllogistic structure for at most a very limited part of practical thinking, the final step which actually issues in the performance of an action," Reason and Human Good in Aristotle, (Cambridge: Harvard University Press, 1975), p. 24.

26. Thomas's major premise parallels Aristotle's in terms of its specific scope. The example from Nicomachean Ethics 1147a illustrates this well: "dry food is good for every man."

27. Thomas Gilby, Summa Theologica (Blackfriars), Vol. l8, "Introduction," p. l57; Vol. 28, p. 8, note h.

28. John Cooper, Reason and Human Good in Aristotle, p. 51.

29. D.K. Modrak, "Aisthesis in the Practical Syllogism," Philosophical Studies, (1976), pp. 379-391.

30. For Modrak, the major premise, minor premise and conclusion to the practical syllogism are all perceptions indicating propositions. This point, though, does not concern us here.

31. Roger A. Shiner "Aisthesis, Nous and Phronesis in the Practical Syllogism," Philosophical Studies, (1979), pp. 377-387.

32. Cooper, p. 58.

33. The Blackfriars edition translates this "In deciding to act, the mind constructs a syllogism the conclusion of which is a judgment or a choice." The final clause "the conclusion of which..." does not capture Thomas's intentions, as I show further.

34. Robert Audi, "A Theory of Practical Reasoning," American Philosophical Quarterly, (1982), pp. 29-30.

35. William Wollaston, The Religion of Nature, in British Moralists, ed. Selby-Bigge (Oxford: Clarendon Press, 1897), pp. 362.