1. IMMANUEL KANT
German philosopher Immanuel Kant (1724-1804) was born in Königsberg, the capital of what was then East Prussia. He studied at the University of Königsberg, became a lecturer there in 1755, and finally in 1770 was appointed Professor of Logic and Metaphysics. Although Kant spent virtually all of his life in and around Königsberg, he was an avid reader of philosophical and scientific authors from other countries – especially France and England – which gave his own prolific writings a cosmopolitan feel. In 1781 he published his most influential work, the Critique of Pure Reason. The work is lengthy, technical, and, by his own confession, somewhat dry. To help readers follow its basic themes Kant wrote a summary, which appeared in 1783 under the title Prolegomena to Any Future Metaphysics (1783). Shortly after, Kant produced two influential works in moral theory: The Groundwork of the Metaphysics of Morals (1785) and the Critique of Practical Reason (1788). Kant retired from teaching in 1797 and died in 1804. The selections below are from Kant’s Prolegomena and Groundwork.
Kant’s philosophy in the Critique of Pure Reason and the Prolegomena is an attempt to resolve the dispute between rationalists and empiricists regarding the source of our foundational philosophical concepts. Descartes, for example, believed that causality is an innate idea that we know a priori. The term a priori refers to a type of instinctive or intuitive knowledge that we gain without any appeal to sense perception and experience. By contrast, empiricists, such as Locke and Hume, believed that our notion of causality is not innate, but instead known a posteriori. A posteriori knowledge, also called empirical knowledge, refers to experiential knowledge that we gain through our external senses or through introspectively experiencing our own feelings and mental operations. Kant opens the Prolegomena by discussing the rationalist/empiricist dispute over the idea of causality.
Implications of Hume’s Problem of Causality. Kant felt that Hume successfully pointed out problems with the standard rationalist view that our knowledge of cause-effect relations is a priori. However, Kant resisted Hume’s conclusion that we know causality empirically. Thus, Kant believes that we still need to address the problem that Hume raises with an alleged a priori notion of causality.
Since the Essays of Locke and Leibniz, or rather since the origin of metaphysics so far as we know its history, nothing has ever happened which was more decisive to its fate than the attack made upon it by David Hume. He threw no light on this species of knowledge, but he certainly struck a spark from which light might have been obtained, had it caught some inflammable substance and had its smoldering fire been carefully nursed and developed.
Hume started from a single but important concept in Metaphysics, namely, that of Cause and Effect (including its derivatives force and action, etc.). He challenges reason, which pretends to have given birth to this idea from herself, to answer him by what right she thinks anything to be so constituted, that if that thing be posited, something else also must necessarily be posited; for this is the meaning of the concept of cause. He demonstrated irrefutably that it was perfectly impossible for reason to think a priori and by means of concepts a combination involving necessity. We cannot at all see why, in consequence of the existence of one thing, another must necessarily exist, or how the concept of such a combination can arise a priori. Hence he inferred, that reason was altogether deluded with reference to this concept, which she erroneously considered as one of her children, whereas in reality it was nothing but a bastard of imagination, impregnated by experience, which subsumed certain representations under the Law of Association, and mistook the subjective necessity of habit for an objective necessity arising from insight. Hence he inferred that reason had no power to think such, combinations, even generally, because her concepts would then be purely fictitious, and all her pretended a priori cognitions nothing but common experiences marked with a false stamp. In plain language there is not, and cannot be, any such thing as metaphysics at all.
However hasty and mistaken Hume’s conclusion may appear, it was at least founded upon investigation, and this investigation deserved the concentrated attention of the brighter spirits of his day as well as determined efforts on their part to discover, if possible, a happier solution of the problem in the sense proposed by him, all of which would have speedily resulted in a complete reform of the science.
(1) According to Kant, what did Hume infer from the problem of causality regarding human reason?
Hume’s Critics and the Larger Implication of Hume’s Problem. Some of Hume’s fellow Scottish philosophers – specifically Thomas Reid, James Oswald, and James Beattie – criticized Hume on the grounds that causality appears to be a dictate of common sense, which we cannot do without. Kant argues that Hume’s critics not only misunderstood Hume, but they also failed to see that Hume’s problem of causality was part of a much larger problem that we find with many other key notions in metaphysics.
But Hume suffered the usual misfortune of metaphysicians, of not being understood. It is positively painful to see bow utterly his opponents, Reid, Oswald, Beattie, and lastly Priestley, missed the point of the problem; for while they were ever taking for granted that which he doubted, and demonstrating with zeal and often with impudence that which he never thought of doubting, they so misconstrued his valuable suggestion that everything remained in its old condition, as if nothing had happened.
The question was not whether the concept of cause was right, useful, and even indispensable for our knowledge of nature, for this Hume had never doubted; but whether that concept could be thought by reason a priori, and consequently whether it possessed an inner truth, independent of all experience, implying a wider application than merely to the objects of experience. This was Hume’s problem. It was a question concerning the origin, not concerning the indispensable need of the concept. Were the former decided, the conditions of the use and the sphere of its valid application would have been determined as a matter of course.
(2) According to Kant, what is the central question raised by Hume’s problem of causality?
Kant’s reaction to Hume. Kant continues noting the profound impact that Hume’s problem had on Kant personally, and how it forced him to re-evaluate the entire subject of metaphysics.
But to satisfy the conditions of the problem, the opponents of the great thinker should have penetrated very deeply into the nature of reason, so far as it is concerned with pure thinking, – a task which did not suit them. They found a more convenient method of being defiant without any insight, namely, the appeal to common sense. It is indeed a great gift of God, to possess right, or (as they now call it) plain common sense. But this common sense must be shown practically, by well-considered and reasonable thoughts and words, not by appealing to it as an oracle, when no rational justification can be advanced. To appeal to common sense, when insight and science fail, and no sooner-this is one of the subtle discoveries of modern times, by means of which the most superficial ranter can safely enter the lists with the most thorough thinker, and hold his own. But as long as a particle of insight remains, no one would think of having recourse to this subterfuge. For what is it but an appeal to the opinion of the multitude, of whose applause the philosopher is ashamed, while the popular charlatan glories and confides in it? I should think that Hume might fairly have laid as much claim to common sense as Beattie, and in addition to a critical reason (such as the latter did not possess), which keeps common sense in check and prevents it from speculating, or, if speculations are under discussion restrains the desire to decide because it cannot satisfy itself concerning its own arguments. By this means alone can common sense remain sound. Chisels and hammers may suffice to work a piece of wood, but for steel-engraving we require an engraver’s needle. Thus common sense and speculative understanding are each serviceable in their own way, the former in judgments which apply immediately to experience, the latter when we judge universally from mere concepts, as in metaphysics, where sound common sense, so called in spite of the inapplicability of the word, has no right to judge at all.
I openly confess, the suggestion of David Hume was the very thing, which many years ago first interrupted my dogmatic slumber, and gave my investigations in the field of speculative philosophy quite a new direction. I was far from following him in the conclusions at which he arrived by regarding, not the whole of his problem, but a part, which by itself can give us no information. If we start from a well-founded, but undeveloped, thought, which another has bequeathed to us, we may well hope by continued reflection to advance farther than the acute man, to whom we owe the first spark of light.
I therefore first tried whether Hume’s objection could not be put into a general form, and soon found that the concept of the connection of cause and effect was by no means the only idea by which the understanding thinks the connection of things a priori, but rather that metaphysics consists altogether of such connections. I sought to ascertain their number, and when I had satisfactorily succeeded in this by starting from a single principle, I proceeded to the deduction of these concepts, which I was now certain were not deduced from experience, as Hume had apprehended, but sprang from the pure understanding. This deduction (which seemed impossible to my acute predecessor, which bad never even occurred to anyone else, though no one had hesitated to use the concepts without investigating the basis of their objective validity) was the most difficult task ever undertaken in the service of metaphysics; and the worst was that metaphysics, such as it then existed, could not assist me in the least, because this deduction alone can render metaphysics possible. But as soon as I had succeeded in solving Hume’s problem not merely in a particular case, but with respect to the whole faculty of pure reason, I could proceed safely, though slowly, to determine the whole sphere of pure reason completely and from general principles, in its circumference as well as in its contents. This was required for metaphysics in order to construct its system according to a reliable method. [Prolegomena, Introduction]
(3) According to Kant, Hume ultimately solved the problem of causality by contending that our experience (and not our a priori reason) gives rise to our notion of causality. By contrast, where does Kant think that the notion of causality springs from?
PREAMBLE ON THE PECULIARITIES OF ALL METAPHYSICAL KNOWLEDGE
In the Preamble to the Prolegomena, Kant establishes some terminology and conceptual distinctions upon which his whole philosophy depends.
Metaphysics deals with A Priori Knowledge. Unlike Hume who attempted to ground metaphysical notions such as causality in empirical experience, Kant insists that metaphysics involves a priori knowledge. In that sense, he believes, it is similar to our notions of mathematics.
Sect. 1. If it becomes desirable to formulate any cognition as science, it will be necessary first to determine accurately those peculiar features which no other science has in common with it, constituting its characteristics; otherwise the boundaries of all sciences become confused, and none of them can be treated thoroughly according to its nature.
The characteristics of a science may consist of a simple difference of object, or of the sources of cognition, or of the kind of cognition, or perhaps of all three conjointly. On this, therefore, depends the idea of a possible science and its territory.
First, as concerns the sources of metaphysical cognition, its very concept implies that they cannot be empirical. Its principles (including not only its maxims but its basic notions) must never be derived from experience. It must not be physical but metaphysical knowledge, namely, knowledge lying beyond experience. It can therefore have for its basis neither external experience, which is the source of physics proper, nor internal, which is the basis of empirical psychology. It is therefore a priori knowledge, coming from pure Understanding and pure Reason.
But so far Metaphysics would not be distinguishable from pure Mathematics; it must therefore be called pure philosophical cognition; and for the meaning of this term I refer to the Critique of the Pure Reason (II. “Method of Transcendentalism,” Chap. I., Sec. 1), where the distinction between these two employments of the reason is sufficiently explained. So far concerning the sources of metaphysical cognition.
(4) According to Kant, what are some of the central features of metaphysical knowledge?
Analytical Judgments. Further clarifying the a priori nature of metaphysical notions, Kant distinguishes between two types of judgments: analytical and synthetical. Analytical judgments involve statements in which the predicate are contained in the subject, such as “All bachelors are unmarried men” and “triangles have three angles.” These statements are true or false based on the definitions of the words themselves; they also do not provide any new information beyond what is already stated in the subject of the statement. Synthetic statements, by contrast, do not have the predicate contained in the subject, such as “the door is brown.” As such, they are not true by definition; for example, the notion of “brown” is not part of the notion of “door”. Further, analytical statements provide us with new information – in this case, information that a particular object is brown.
Sect. 2. a. Of the Distinction between Analytical and Synthetical judgments in general. – The peculiarity of its sources demands that metaphysical cognition must consist of nothing but a priori judgments. But whatever be their origin, or their logical form, there is a distinction in judgments, as to their content, according to which they are either merely explicative, adding nothing to the content of the cognition, or expansive, increasing the given cognition: the former may be called analytical, the latter synthetical, judgments.
Analytical judgments express nothing in the predicate but what has been already actually thought in the concept of the subject, though not so distinctly or with the same (full) consciousness. When I say: All bodies are extended, I have not amplified in the least my concept of body, but have only analyzed it, as extension was really thought to belong to that concept before the judgment was made, though it was not expressed, this judgment is therefore analytical. On the contrary, this judgment, All bodies have weight, contains in its predicate something not actually thought in the general concept of the body; it amplifies my knowledge by adding something to my concept, and must therefore be called synthetical.
b. The Common Principle of all Analytical Judgments is the Law of Contradiction. – All analytical judgments depend wholly on the law of Contradiction, and are in their nature a priori cognitions, whether the concepts that supply them with matter be empirical or not. For the predicate of an affirmative analytical judgment is already contained in the concept of the subject, of which it cannot be denied without contradiction. In the same way its opposite is necessarily denied of the subject in an analytical, but negative, judgment, by the same law of contradiction. Such is the nature of the judgments: all bodies are extended, and no bodies are unextended (i. e., simple).
For this very reason all analytical judgments are a priori even when the concepts are empirical, as, for example, Gold is a yellow metal; for to know this I require no experience beyond my concept of gold as a yellow metal: it is, in fact, the very concept, and I need only analyze it, without looking beyond it elsewhere.
(5) Explain how the law of contradiction applies to analytical judgments.
Synthetical Judgments. Turning to synthetical judgments, Kant notes that the most obvious kind of synthetical judgments are empirical (a posteriori), such as “the door is brown,” which we know through visual experience. However, in addition to empirical notions, Kant argues that mathematical and metaphysical judgments are also synthetical.
c. Synthetical judgments require a different Principle from the Law of Contradiction. There are synthetical a posteriori judgments of empirical origin; but there are also others which are proved to be certain a priori, and which spring from pure Understanding and Reason. Yet they both agree in this, that they cannot possibly spring from the principle of analysis, namely, the law of contradiction, alone; they require a quite different principle, though, from whatever they may be deduced, they must be subject to the law of contradiction, which must never be violated, even though everything cannot be deduced from it. I shall first classify synthetical judgments.
1. Empirical judgments are always synthetical. For it would be absurd to base an analytical judgment on experience, as our concept suffices for the purpose without requiring any testimony from experience. That body is extended, is a judgment established a priori, and not an empirical judgment. For before appealing to experience, we already have all the conditions of the judgment in the concept, from which we have but to elicit the predicate according to the law of contradiction, and thereby to become conscious of the necessity of the judgment, which experience could not even teach us.
2. Mathematical judgments are all synthetical. This fact seems hitherto to have altogether escaped the observation of those who have analyzed human reason; it even seems directly opposed to all their conjectures, though incontestably certain, and most important in its consequences. For as it was found that the conclusions of mathematicians all proceed according to the law of contradiction (as is demanded by all apodictic certainty), men persuaded themselves that the fundamental principles were known from the same law. This was a great mistake, for a synthetical proposition can indeed be comprehended according to the law of contradiction, but only by presupposing another synthetical proposition from which it follows, but never in itself. ...
It might at first be thought that the proposition 7+5=12 is a mere analytical judgment, following from the concept of the sum of seven and five, according to the law of contradiction. But on closer examination it appears that the concept of the sum Of 7+5 contains merely their union in a single number, without its being at all thought what the particular number is that unites them. The concept of twelve is by no means thought by merely thinking of the combination of seven and five; and analyze this possible sum as we may, we shall not discover twelve in the concept. We must go beyond these concepts, by calling to our aid some concrete image, i.e., either our five fingers, or five points (as Segner has it in his Arithmetic), and we must add successively the units of the five, given in some concrete image, to the concept of seven. Hence our concept is really amplified by the proposition 7+5=12, and we add to the first a second, not thought in it. Arithmetical judgments are therefore synthetical, and the more plainly according as we take larger numbers; for in such cases it is clear that, however closely we analyze our concepts without calling visual images to our aid, we can never find the sum by such mere dissection.
(6) Although we might initially think that mathematical propositions are analytical (with the predicate contained in the subject), Kant believes that they are synthetic. Illustrating his point with the proposition “7+5=12” what does he say about the relation between the predicate “12” and the subject “7+5”?
Metaphysical Synthetic A Priori Judgments. Like mathematical judgments, Kant believes that metaphysical judgments are also synthetic a priori. That is, they are non-empirical yet provide us with new information.
Metaphysical judgments, properly so called, are all synthetical. We must distinguish judgments pertaining to metaphysics from metaphysical judgments properly so called. Many of the former are analytical, but they only afford the means for metaphysical judgments, which are the whole end of the science, and which are always synthetical. For if there be concepts pertaining to metaphysics (as, for example, that of substance), the judgments springing from simple analysis of them also pertain to metaphysics, as, for example, substance is that which only exists as subject; and by means of several such analytical judgments, we seek to approach the definition of the concept. But as the analysis of a pure concept of the understanding pertaining to metaphysics, does not proceed in any different manner from the dissection of any other, even empirical, concepts, not pertaining to metaphysics (such as: air is an elastic fluid, the elasticity of which is not destroyed by any known degree of cold), it follows that the concept indeed, but not the analytical judgment, is properly metaphysical. This science has something peculiar in the production of its a priori cognitions, which must therefore be distinguished from the features it has in common with other rational knowledge. Thus the judgment, that all the substance in things is permanent, is a synthetical and properly metaphysical judgment. ...
The conclusion drawn in this section then is, that metaphysics is properly concerned with synthetical propositions a priori, and these alone constitute its end, for which it indeed requires various dissections of its concepts, namely, of its analytical judgments, but wherein the procedure is not different from that in every other kind of knowledge, in which we merely seek to render our concepts distinct by analysis. But the generation of a priori cognition by concrete images as well as by concepts—in short, of synthetical propositions a priori in philosophical cognition—constitutes the essential subject of Metaphysics.
(7) Although some judgments pertaining to metaphysics are analytical, Kant believes that metaphysical judgments properly speaking are synthetical. Give one of Kant’s examples of a synthetical metaphysical judgment.
Kant argues that the success of metaphysics depends on our ability to show how synthetic a priori judgments are even possible. That is, we need to see how the mechanism of human reason provides us with intuitive (non-empirical) knowledge that contains new information.
Sect. 5. We have above learned the significant distinction between analytical and synthetical judgments. The possibility of analytical propositions was easily comprehended, being entirely founded on the law of Contradiction. The possibility of synthetical a posteriori judgments, of those which are gathered from experience, also requires no particular explanation; for experience is nothing but a continual synthesis of perceptions. There remain therefore only synthetical propositions a priori, of which the possibility must be sought or investigated, because they must depend upon principles other than the law of contradiction.
But here we need not first establish the possibility of such propositions so as to ask whether they are possible. For there are enough of them which indeed are of undoubted certainty, and as our present method is analytical, we shall start from the fact, that such synthetical but purely rational cognition actually exists; but we must now inquire into the reason of this possibility, and ask, how such cognition is possible, in order that we may from the principles of its possibility be enabled to determine the conditions of its use, its sphere and its limits. The proper problem upon which all depends, when expressed with scholastic precision, is therefore: How are Synthethetic Propositions a priori possible? ...
Metaphysics stands or falls with the solution of this problem: its very existence depends upon it. Let any one make metaphysical assertions with ever so much plausibility, let him overwhelm us with conclusions, if he has not previously proved able to answer this question satisfactorily, I have a right to say this is all vain baseless philosophy and false wisdom. You speak through pure reason, and claim, as it were to create cognitions a priori by not only dissecting given concepts, but also by asserting connections which do not rest upon the law of contradiction, and which you believe you conceive quite independently of all experience; how do you arrive at this, and how will you justify your pretensions? An appeal to the consent of the common sense of mankind cannot be allowed; for that is a witness whose authority depends merely upon rumor. Says Horace: “To all that which you prove me in this manner, I refuse to give credence.” [Prolegomena, Preamble]
(8) According to Kant, why can’t we prove our metaphysical assertions by appealing to the common consent of humankind?
To answer the crucial question of how synthetic a priori judgments are possible, Kant divides the question into four separate questions, and addresses each of these individually: 1. How is pure mathematics possible? 2. How is pure natural science possible? 3. How is metaphysics in general possible? 4. How is metaphysics as a science possible?
HOW IS PURE MATHEMATICS POSSIBLE?
Kant believes that our notions of space and time are intimately connected with all judgments in mathematics. Our purest notions of space and time are instinctive components of our thinking and we do not simply infer them from our sensory experience of the physical world. In fact, to even make sense of our confusing sensory experiences, we must already have the mental concepts of space and time. In Kant’s words, our sense experiences provide us with the material of our perception, but our underlying intuitions of space and time provide its form.
Concepts of Space and Time underlie Mathematics. Granting that we have these inborn concepts of space and time, Kant believes that these concepts answer the question of “ how is pure mathematics possible”. For Kant, when we make synthetic a priori mathematical judgments, we draw from our concepts of space and time. This is seen most clearly in the field of geometry, which is the science of our pure concepts of space.
Sect. 10. Now, the intuitions which pure mathematics lays at the foundation of all its cognitions and judgments which appear at once apodictic and necessary are Space and Time. For mathematics must first have all its concepts in intuition, and pure mathematics in pure intuition, that is, it must construct them. If it proceeded in any other way, it would be impossible to make any headway, for mathematics proceeds, not analytically by dissection of concepts, but synthetically, and if pure intuition be wanting, there is nothing in which the matter for synthetical judgments a priori can be given. Geometry is based upon the pure intuition of space. Arithmetic accomplishes its concept of number by the successive addition of units in time; and pure mechanics especially cannot attain its concepts of motion without employing the representation of time. Both representations, however, are only intuitions; for if we omit from the empirical intuitions of bodies and their alterations (motion) everything empirical, or belonging to sensation, space and time still remain, which are therefore pure intuitions that lie a priori at the basis of the empirical. Hence they can never be omitted, but at the same time, by their being pure intuitions a priori, they prove that they are mere forms of our sensibility, which must precede all empirical intuition, or perception of actual objects, and conformably to which objects can be known a priori, but only as they appear to us.
Sect. 11. The problem of the present section is therefore solved. Pure mathematics, as synthetical cognition a priori, is only possible by referring to no other objects than those of the senses. At the basis of their empirical intuition lies a pure intuition (of space and of time) which is a priori. This is possible, because the latter intuition is nothing but the mere form of sensibility, which precedes the actual appearance of the objects, insofar as it, in fact, makes them possible. Yet this faculty of intuiting a priori affects not the matter of the phenomenon (that is, the sense-element in it, for this constitutes that which is empirical), but its form, namely, space and time. Should any man venture to doubt that these are determinations adhering not to things in themselves, but to their relation to our sensibility, I should be glad to know how it can be possible to know the constitution of things a priori, namely, before we have any acquaintance with them and before they are presented to us. Such, however, is the case with space and time. But this is quite comprehensible as soon as both count for nothing more than formal conditions of our sensibility, while the objects count merely as phenomena; for then the form of the phenomenon, i.e., pure intuition, can by all means be represented as proceeding from ourselves, that is, a priori.
(9) Kant argues that when we make synthetic a priori mathematical judgments we refer only to objects of the senses. What, in turn, is at the basis of our empirical sensory experiences?
Trancendental Idealism. In the Critique of Pure Reason Kant dubbed his theory of space and time “transcendental idealism,” by which he meant that pure notions of space and time are grounded only in our cognitive faculties, and are not derived through our experience of the world (“transcendental” being Kant’s word for our cognitive faculties). Unfortunately for Kant, the term “idealism” is a loaded word in philosophy, and, in its extreme form, such as we find in Berkeley, it involves a complete denial of the external material world. Kant denies that he is an idealist in this extreme sense.
Remark 3. ... I have myself given this my theory the name of transcendental idealism, but that cannot authorize any one to confound it either with the empirical idealism of Descartes, (indeed, his was only an insoluble problem, owing to which he thought everyone at liberty to deny the existence of the corporeal world, because it could never be proved satisfactorily), or with the mystical and visionary idealism of Berkeley, against which and other similar phantasms our Critique contains the proper antidote. My idealism concerns not the existence of things (the doubting of which, however, constitutes idealism in the ordinary sense), since it never came into my head to doubt it, but it concerns the sensuous representation of things, to which space and time especially belong. Of these [namely, space and time], consequently of all appearances in general, I have only shown, that they are neither things (but mere modes of representation), nor determinations belonging to things in themselves. But the word “transcendental,” which with me means a reference of our cognition, i.e., not to things, but only to the cognitive faculty, was meant to obviate this misconception. Yet rather than give further occasion to it by this word, I now retract it, and desire this idealism of mine to be called critical. But if it be really an objectionable idealism to convert actual things (not appearances) into mere representations, by what name shall we call him who conversely changes mere representations to things? It may, I think, be called “dreaming idealism,” in contradistinction to the former, which may be called “visionary,” both of which are to be refuted by my transcendental, or, better, critical idealism.
(10) Kant argues that his transcendental idealism does not concern the existence of things; instead, what does it involve?
HOW IS THE SCIENCE OF NATURE POSSIBLE?
Solving the first question regarding mathematics, Kant turns to the second question, which concerns how the science of nature is possible. More exactly, Kant investigates the underlying cognitive principles that allow us to make judgments about things in the physical world.
Phenomena and Noumena. Throughout his writings, Kant relies on an important distinction between what he calls phenomena and noumena. Phenomena involve what I actually experience, and noumena involve things as they are in themselves apart from how I might experience them. For example, as I look at a desk I can make a list of all of its physical features that appear to my five senses, such as its color and texture. Apart from this list of sensory phenomena, though, there still remain features about the desk that I have no way of investigating or even describing. These hidden features are the noumena of the desk, and I am permanently prevented from knowing them. Kant argues here that our experience of the physical world is in general restricted to the phenomena, and cannot reveal anything about noumenal things in themselves.
Sect. 14. Nature is the existence of things, so far as it is determined according to universal laws. Should nature signify the existence of things in themselves, we could never know it either a priori or a posteriori. Not a priori, for how can we know what belongs to things in themselves, since this never can be done by the dissection of our concepts (in analytical judgments)? We do not want to know what is contained in our concept of a thing (for the [concept describes what] belongs to its logical being), but what is in the actuality of the thing superadded to our concept, and by what the thing itself is determined in its existence outside the concept. Our understanding, and the conditions on which alone it can connect the determinations of things in their existence, do not prescribe any rule to things themselves; these do not conform to our understanding, but it must conform itself to them; they must therefore be first given us in order to gather these determinations from them, wherefore they would not be known a priori.
A cognition of the nature of things in themselves a posteriori would be equally impossible. For, if experience is to teach us laws, to which the existence of things is subject, these laws, if they regard things in themselves, must belong to them of necessity even outside our experience. But experience teaches us what exists and how it exists, but never that it must necessarily exist so and not otherwise. Experience therefore can never teach us the nature of things in themselves.
(11) Why can’t we investigate things in themselves through a posteriori (i.e., empirical) reasoning?
Table of Judgments and the Categories. Kant argued earlier that our instinctive cognitive notions of space and time help organize the confusing influx of raw sensory perceptions that rush in through our senses. Kant argues further that in order to think about our various perceptions, we need additional instinctive cognitive notions that organize these experiences. He lays these out in two tables. The first (the logical table of judgments) shows the complete range of judgments that we in fact make about physical things. From this first table he derives the second one (the transcendental table of the pure concepts of the understanding); this lists the complete range of cognitive categories that we need to make all the judgments in the first table. Kant refers to the second table as a list of conceptual categories, which he believes supersedes Aristotle’s list of categories. Suppose, for example, that I make the judgment “all cows eat grass,” which, according to the first table, would be a universal judgment about quantity. For me to make this judgment about all cows, though, I need to first have a concept of “unity,” which is the first item in the second table. Thus, the twelve items in the two tables parallel each other, and are presented in four groups of three items.
Sect. 21. To prove, then, the possibility of experience so far as it rests upon pure concepts [i.e., categories] of the understanding a priori, we must first represent what belongs to judgments in general and the various functions of the understanding, in a complete table. For the pure concepts of the understanding must run parallel to these functions, as such concepts are nothing more than concepts of intuitions in general, so far as these are determined by one or other of these functions of judging in themselves, that is, necessarily and universally. Hereby also the a priori principles of the possibility of all experience, as of an objectively valid empirical cognition, will be precisely determined. For they are nothing but propositions by which all perception is (under certain universal conditions of intuition) subsumed under those pure concepts of the understanding.
LOGICAL TABLE OF JUDGMENTS.
1. As to Quantity.
2. As to Quality.
3. As to Relation.
4. As to Modality.
TRANSCENDENTAL TABLE OF THE PURE CONCEPTS OF THE UNDERSTANDING [i.e., THE CATEGORIES].
1. As to Quantity.
Unity (the Measure).
Plurality (the Quantity).
Totality (the Whole).
2. As to Quality.
3. As to Relation.
4. As to Modality.
(12) The statement “all cows eat grass” is an example of a universal judgment regarding quantity. Make up a statement that illustrates another type of judgment on the first table.
The Categories as Universal Rules of Possible Experience. Kant argues that, in order for me to make any kind of judgment, my various experiences must be united within my own consciousness. It must also be united in a way that would hold as a rule for anyone’s experience. Otherwise, each of us would have an entirely different way of judging the world. Thus, the universal nature of the categories – or rules of possible experience –provides the solution to the question “How is the science of nature possible.” The answer is that universal categories constitute “universal laws of nature,” which allow us to scientifically investigate nature.
Sect. 22. The sum of the matter is this: the business of the senses is to intuit – that of the understanding is to think. But thinking is uniting representations in one consciousness. ...
Sect. 23. Judgments, when considered merely as the condition of the union of given representations in a consciousness, are rules. These rules, so far as they represent the union as necessary, are rules a priori, and so far as they cannot be deduced from higher rules, are fundamental principles. But in regard to the possibility of all experience, merely in relation to the form of thinking in it, no conditions of judgments of experience are higher than those which bring the phenomena, according to the various form of their intuition, under pure concepts of the understanding, and render the empirical judgment objectively valid. These concepts are therefore the a priori principles of possible experience.
The principles of possible experience are then at the same time universal laws of nature, which can be known a priori. And thus the problem in our second question, “How is the pure Science of Nature possible?” is solved. For the system which is required for the form of a science is to be met with in perfection here, because, beyond the above-mentioned formal conditions of all judgments in general offered in logic, no others are possible, and these constitute a logical system. The concepts grounded thereupon, which contain the a priori conditions of all synthetical and necessary judgments, accordingly constitute a transcendental system. Finally the principles, by means of which all phenomena are subsumed under these concepts, constitute a physical system, that is, a system of nature, which precedes all empirical cognition of nature, makes it even possible, and hence may in strictness be denominated the universal and pure science of nature.
(13) In what sense are the rules of possible experience a priori?
The Categories involve Phenomena, not Noumena. Kant stresses that the above tables do not apply to things in themselves, but only to our mental arrangement of the phenomena that we experience.
Sect. 30 ... This is therefore the result of all our foregoing inquiries: “All synthetical principles a priori are nothing more than principles of possible experience, and can never be referred to things in themselves, but to appearances as objects of experience. And hence pure mathematics as well as a pure science of nature can never be referred to anything more than mere appearances, and can only represent either that which makes experience generally possible, or else that which, as it is derived from these principles, must always be capable of being represented in some possible experience.”
Sect. 31. And thus we have at last something definite, upon which to depend in all metaphysical enterprises, which have hitherto, boldly enough but always at random, attempted everything without discrimination. That the aim of their exertions should be so near, struck neither the dogmatical thinkers nor those who, confident in their supposed sound common sense, started with concepts and principles of pure reason (which were legitimate and natural, but destined for mere empirical use) in quest of fields of knowledge, to which they neither knew nor could know any determinate bounds, because they bad never reflected nor were able to reflect on the nature or even on the possibility of such a pure understanding.
(14) What must both pure mathematics and the pure science of nature refer to?
HOW IS METAPHYSICS IN GENERAL POSSIBLE?
Metaphysics is an investigation into the nature of reality, and often involves speculations about the existence of God, a spirit-realm, and the causes of the universe. The next question that Kant seeks to answer is “How is metaphysics in general possible.” Kant is suspicious of any dogmatic metaphysics that strays beyond the phenomenal world of appearances into the unknowable noumenal realm of things in themselves. Thus, he aims to dismiss many traditional metaphysical discussions and instead restrict metaphysics to the domain of possible experience as defined by the categories.
Applying the Categories beyond Experience. For Kant, the categories are required for ordering our experience of the physical world. However, he explains that it is tempting to apply the categories when thinking about metaphysical issues beyond the realm of experience.
Sect. 45. We have above shown ... that the purity of the categories from all admixture of sensuous determinations may mislead reason into extending their use, quite beyond all experience, to things in themselves. Though as these categories themselves find no intuition which can give them meaning or sense in concrete, they, as mere logical functions, can represent a thing in general, but not give by themselves alone a determinate concept of anything. Such hyperbolical objects are distinguished by the appellation of Noumena, or pure beings of the understanding (or better, beings of thought), such as, for example, “substance,” but conceived without permanence in time, or “cause,” but not acting in time, etc. Here predicates, that only serve to make the conformity-to-law of experience possible, are applied to these concepts, and yet they are deprived of all the conditions of intuition, on which alone experience is possible, and so these concepts lose all significance.
There is no danger, however, of the understanding spontaneously making an excursion so very wantonly beyond its own bounds into the field of the mere creatures of thought, without being impelled by foreign laws. But when reason, which cannot be fully satisfied with any empirical use of the rules of the understanding, as being always conditioned, requires a completion of this chain of conditions, then the understanding is forced out of its sphere. And then it partly represents objects of experience in a series so extended that no experience can grasp, partly even (with a view to complete the series) it seeks entirely beyond it noumena, to which it can attach that chain, and so, having at last escaped from the conditions of experience, make its attitude as it were final. These are then the transcendental ideas, which, though according to the true but hidden ends of the natural determination of our reason, they may aim not at extravagant concepts, but at an unbounded extension of their empirical use, yet seduce the understanding by an unavoidable illusion to a transcendent use, which, though deceitful, cannot be restrained within the bounds of experience by any resolution, but only by scientific instruction and with much difficulty.
(15) What causes the understanding to be “forced out of its sphere”?
The Antinomies. As we apply the categories when thinking about metaphysical issues beyond the realm of experience, we will inevitably be led into conflicting views on four specific issues. Kant argues that these four issues correspond with the four main divisions of the categories.
Sect. 51. In the first place, the use of a system of categories becomes here so obvious and unmistakable, that even if there were not several other proofs of it, this alone would sufficiently prove it indispensable in the system of pure reason. There are only four such transcendent ideas, as there are so many classes of categories; in each of which, however, they refer only to the absolute completeness of the series of the conditions for a given conditioned. In analogy to these cosmological ideas there are only four kinds of dialectical assertions of pure reason, which, as they are dialectical, thereby prove, that to each of them, on equally specious principles of pure reason, a contradictory assertion stands opposed. As all the metaphysical art of the most subtle distinction cannot prevent this opposition, it compels the philosopher to recur to the first sources of pure reason itself. This Antinomy, not arbitrarily invented, but founded in the nature of human reason, and hence unavoidable and never ceasing, contains the following four theses together with their antitheses:
Thesis: The World has, as to, Time and Space, a Beginning (limit).
Antithesis: The World is, as to Time and Space, infinite.
Thesis: Everything in the World consists of [elements that are] simple.
Antithesis: There is nothing simple, but everything is composite.
Thesis: There are in the World Causes through Freedom.
Antithesis: There is no Liberty, but all is Nature.
Thesis: In the Series of the World-Causes there is some necessary Being.
Antithesis: There is Nothing necessary in the World, but in this Series All is incidental.
(16) According to Kant, these antinomies are “not arbitrarily invented”; instead, what are they founded on?
What is most troubling about the antinomies, according to Kant, is that we might employ rock-solid reasoning in defense of each of the theses and antitheses.
Sect. 52. Here is the most singular phenomenon of human reason, no other instance of which can be shown in any other use. If we, as is commonly done, represent to ourselves the appearances of the sensible world as things in themselves, if we assume the principles of their combination as principles universally valid of things in themselves and not merely of experience, as is usually, nay without our Critique, unavoidably done, there arises an unexpected conflict, which never can be removed in the common dogmatical way; because the thesis, as well as the antithesis, can be shown by equally clear, evident, and irresistible proofs – for I pledge myself as to the correctness of all these proofs – and reason therefore perceives that it is divided with itself, a state at which the skeptic rejoices, but which must make the critical philosopher pause and feel ill at ease. ...
(17) What reaction might a skeptic have in showing the inherently contradictory nature of human reasoning?
Unlike the skeptic, Kant comes to reason’s defense and attempts to explain away the antinomies. Ultimately, he rejects each of the theses and antitheses in the first two antinomies, since they are self-contradictory. However, he accepts each of the theses and antitheses in the final two antinomies since he believes that we can hold these compatibly.