Kant s Prolegomena to Any Future Metaphysics

1. Kant�sProlegomena to Any Future Metaphysics An Introduction to the Critique of Pure Reason

2. Prolegomena, Introduction Kant�s Prolegomena, intended as an introduction to his Critique of Pure Reason, is itself by no means an easy book to read In the Introduction, which is largely historical, Kant says a bit about what led him to the idea of undertaking the Critique in the first place, says a word or two about his aim in writing the Prolegomena (which was, of course, to clarify that earlier work), and ends by writing: [S]hould any reader find this sketch, which I publish as�Prolegomena to Any Future Metaphysics, still obscure, let him consider that not everyone is bound to study metaphysics; that many minds will succeed very well in the exact and even in deep sciences more closely allied to the empirical, while they cannot succeed in investigations dealing exclusively with abstract concepts. In such cases, men should apply their talents to other subjects. But he who undertakes to judge or, still more, to construct a system of metaphysics must satisfy the demands here made, either by adopting my solution or by thoroughly refuting it and substituting another. To evade it is impossible. (11)

3. Prolegomena, Preamble Immediately following the Introduction, Kant turns, in a section of the text entitled �Preamble on the Peculiarities of All Metaphysical Knowledge,� to the task of setting up the main problem that was addressed in the Critique, and that must therefore be addressed in the Prolegomena as well�i.e., the problem that we�ve already encountered as that of how synthetic propositions a priori are possible As his aim is now to set the problem up, he begins, in two sections entitled �Of the Sources of Metaphysics� and �Concerning the Kind of Knowledge Which Can Alone Be Called Metaphysical� with a set of remarks clearly designed to lay the foundations of the two crucial distinctions: The distinction between knowledge a priori and knowledge a posteriori The distinction between analytic and synthetic judgments so to these we must ourselves now turn�

4. Prolegomena, Preamble Knowledge a priori and knowledge a posteriori. In his discussion in the Prolegomena, Kant introduces this distinction more or less on the fly (in the context of a set of remarks on the source of metaphysical knowledge) by contrasting Knowledge the source of which is empirical, i.e., knowledge derived either from external or internal experience, with Knowledge a priori, i.e., �knowledge coming from pure understanding and pure reason� (13) The first of these, of course, is knowledge a posteriori, which might therefore be defined as knowledge coming from experience In deciding to use the terms �a posteriori� and �a priori� in this way, Kant departs from an earlier tradition of using them to express the distinction between knowledge gotten by what Aristoteles called �induction� (not what I call �induction�) and knowledge deduced from first principles�quite a different distinction

5. Prolegomena, Preamble Analytic and synthetic judgments. To understand this second distinction, one must first understand that Kant thinks of judgments, in the basic case at any rate, as being �syntheses� (combinations) of concepts such that the �first� concept is a concept of the judgment�s subject while the �second� concept is the judgment�s predicate:

6. Prolegomena, Preamble Putting the two distinctions together, we find ourselves with the following classification The law of contradiction makes it possible for us to know the truth of analytic judgments a priori, and the experience of their subjects makes it possible for us to know the truth of synthetic judgments a posteriori, but what could conceivably make it possible for us to know the truth of synthetic judgments a priori?

7. Prolegomena, Part I In the case of mathematical judgments, Kant argues that the only possible solution is that space and time themselves, as the mere forms of our sensibility (30), are capable of being given to us in pure intuition (i.e., a priori) If they are, then we can understand how we can grasp the truth of synthetic propositions a priori in mathematics, for Concepts are, in general, rules, and In mathematics, we proceed by the �construction of concepts� (17), i.e., by using our concepts of numbers and shapes as rules for imagining their construction in pure space and pure time. Once we�ve done this, we can use our non-sensory awareness of these figures as a non-empirical basis for whole hosts of synthetic judgments about them This case, then, is an easy one: mathematics is possible because we are capable of having a �non-empirical experience� of the subjects of its judgments; we�re capable of intuiting them a priori

8. Prolegomena, Part I So Part I of the Prolegomena discloses a remarkable truth we couldn�t arrive at in any other way: the space and time of which we are always aware are in the mind, and there may not be, �outside� the mind (i.e., independently of us) any space or time at all There follow immediately these two corollaries: The things we encounter in space and time may not be intrinsically spatial or temporal in character at all, which means that things as they appear to us may be radically different from things as they are in themselves�things as they really are. (Kant likens the revolution he thinks this idea is bound to produce in philosophy to the Copernican revolution in astronomy which rested on the idea that the apparent motions of the heavenly bodies aren�t their real motions at all) Contrary to Descartes and everyone who has followed him, we can now see that we ourselves�we philosophers�can�t really know ourselves either�not, at any rate, by means of any sort of self-experience; in a sense, the knower must remain�unknown

9. Prolegomena, Part II In Part II of the Prolegomena, Kant turns his attention to what he calls �pure science of nature,� and for many readers, the most difficult thing about Part II is getting clear about just what this science is supposed to be Kant clearly thinks that like mathematics, this science gives us knowledge a priori of a number of synthetic propositions, but while it resembles mathematics in being �pure� (non-empirical), it also resembles the empirical sciences of inner and outer nature (i.e., psychology and physics) in being about minds and bodies A good bit of what makes it so difficult for readers of Kant today to understand what science he could have in mind here is that we now tend to think of all science of nature�all knowledge of nature�as something that is almost by definition empirical So perhaps it�s the term �science of nature� that tends to mislead us

10. Prolegomena, Part II The historically minded will remember that traditional metaphysics included not only special metaphysics�rational psychology, rational cosmology, and rational theology�but also what was called general metaphysics�ontology or category theory: what Aristoteles called the science of beings qua beings� and strictly it�s this that Kant has in mind when he speaks, in the Prolegomena, of the non-empirical or pure science of nature But what can we possibly know a priori about minds or bodies other than what we can analyze out of the contents of our concepts of minds and bodies? For Kant the answer is this: what we can know a priori about minds and bodies is what they are as objects of possible experience�their definition, in effect, as objects of possible experience Kant denies that pure science of nature can begin with definitions, but with this science in hand, we can say the following

11. Prolegomena, Part II Every object of possible experience�inner experience as well as outer experience�has the following characteristics: it is extended in space and/or time; everything in it that can manifest itself directly in sensation has, at each moment of time, some precise degree of intensity; a) though changeable (i.e., capable of existing in different states), its substance endures throughout all change and is therefore incapable of being increased or diminished, b) every change that takes place in it takes place in accordance with the law of cause and effect, c) it�s in constant mutual interaction with all the other objects with which it coexists; and finally, a) while its possibility consists in its conceivability and intuitability, b) its actuality, if it does indeed actually exist, is capable, in principle, of being made manifest in some sensation, and c) the necessity of its being in whatever state it�s in at any given time is a function of its immediately preceding state, or more precisely, of the immediately preceding state of the system of which it�s a part

12. Prolegomena, Part II This characterization of objects of possible experience is yielded by the principles that fall under the headings in Kant�s third table in �21, that of the universal principles of the science of nature: (1) Axioms of Intuition (2) Anticipations of Perception (3) Analogies of Experience (4) Postulates of Empirical Thinking Generally The first two Analogies of Experience�3.a and 3.b on the preceding slide�are highlighted by Kant at the beginning of Part II of the Prolegomena in �15 (43); the others are discussed in ��24-26 (54-57) and more fully still in the Critique of Pure Reason (A130=B169 ff). Kant claims that that the Axioms of Intuition and Anticipations of Perception ensure the applicability of mathematics to nature (54), that the Analogies of Experience give us nature�s �real laws� (55), and that the Postulates of Empirical Thinking Generally make clear what possibility, existence, and necessity amount to in nature (55)

13. Prolegomena, Part II The question of Part II of the Prolegomena, of course, is how it�s possible for us to know a priori all these things about objects of possible experience, and the answer Kant gives in Part II is very different from the answer he gave to the corresponding question in Part I Mathematical concepts, you�ll recall, are regarded by Kant as rules for the construction of mathematical figures�shapes and numbers� in pure intuition, but the concepts that go to make up our concept of an object (the so-called �categories� or concepts of the understanding presented in the first table on p. 51) are concepts Kant thinks we use as rules for �decipher[ing] appearances, that we may be able to read them as experience� (60). In other words, while we can�t use these concepts to construct objects a priori in pure intuition, since they�re the rules that give our perception the character of experience, we can use them to establish principles that enable us to know a priori the most general features of objects of any possible experience

14. Prolegomena, Part II Kant�s detailed argument for this thesis�which is contained in the section called the Transcendental Deduction of the Categories in the Critique of Pure Reason�is of legendary difficulty, and what replaces that deduction in the Prolegomena�the discussion of the way in which our judgments of perception are transformed into judgments of experience�suffers from difficulties of its own Suffice it to say, then, that Kant thinks he can prove that it�s our possession a priori of the twelve concepts of the understanding�the concepts he frequently calls the �categories�� that makes our experience of an object possible in the first place. In other words, he thinks he can prove that instead of getting these concepts from our experience of objects, we apply them to the data of our inner and outer sense and use them to interpret our sensations as appearances of objects But then what can be the source of these concepts?

15. Prolegomena, Part II Kant doesn�t think that we�re born with these concepts (i.e., or in other words, that they�re innate ideas in Descartes�s sense of the term), and he has no patience with the Platonic idea that our acquisition of them has the character of some sort of recollection Instead, he thinks that we acquire them as we become aware (even if quite unreflectively) of the forms of judgment of which the human mind is capable�the various forms of judgment enumerated in the table on p. 50 in the Prolegomena Thus he thinks, for example, that we think of objects as substances that have attributes because the most basic judgments we are capable of making are, from a purely logical point of view, categorical judgments: judgments in which something is predicated of something To make a long story short: Kant thinks that the objects of our experience must have the general character that they do because of the very grammar or syntax of our thought

16. Prolegomena, Part II The upshot of Part II of the Prolegomena, then, is the thesis�even more startling than the theses that were the upshot of Part I� that �[T]he understanding does not derive its laws (a priori) from [nature], but prescribes them to [it instead]� (67; bold type mine) Another way of putting this�less dramatic to be sure, but a good deal clearer, and with a clear indication of how Kant thinks the central argument of Part II goes�is as follows: [T]he main proposition expounded throughout this section�that universal laws of nature can be known a priori�leads naturally to the proposition that the highest legislation of nature must lie in ourselves, that is, in our understanding; and that we must not seek the universal laws of nature in nature by means of experience, but conversely must seek nature, as to its universal conformity to law, in the conditions of the possibility of experience which lie in our sensibility and in our understanding. (66) The universal order of nature has its source in the understanding (69)

17. Prolegomena, Part III In Part III of the Prolegomena, Kant turns his attention to special metaphysics�rational psychology, rational cosmology, and rational theology�all of which would, he thinks, have to consist of synthetic judgments we could know to be true a priori if they could exist as actual sciences at all (with regard to this latter point, cf. p. 18) His point of departure for the discussion is the question of just how it is we possess, a priori, the concepts of the subject matters of these three purported sciences: the concepts of the soul, the world (i.e., the whole of the outer world), and God�concepts he characterizes as concepts of pure reason to contrast them with the concepts of pure understanding�the categories�that occupied center stage in Part II His initial characterization of them is as concepts that �aim at the completeness, that is, the collective unity of all possible experience� (76), and he says that insofar as they aim at such completeness, they �transcend every given experience,� tempting us to think that we can know things that aren�t objects of any possible experience (ibid.)

18. Prolegomena, Part III As to the origin of these concepts, Kant says this: As I had found the origin of the categories in the four logical forms of all the judgments of the understanding, it was quite natural to seek the origin of the Ideas [Kant�s regular name for the concepts of the reason] in the three forms of syllogisms�. The formal distinction of syllogisms renders necessary their division into categorical, hypothetical, and disjunctive. The concepts of reason founded on them contain therefore, first, the Idea of the complete subject (the substantial); secondly, the Idea of the complete series of conditions; thirdly, the determination of all concepts in the Idea of a complete complex of that which is possible. The first idea is psychological, the second cosmological, the third theological; and, as all three give occasion to dialectic [Kant�s regular name of fallacious reasoning], yet each in its own way, the division of the whole dialectic of pure reason into its paralogism, its antinomy, and its Ideal [Kant�s regular names for the specific forms of fallacy characteristic of each of the three parts of special metaphysics] was arranged accordingly. (78)

19. Prolegomena, Part III Given this, it�s easy to anticipate the direction of the rest of the analysis of Part III In separate sections on the psychological ideas, the cosmological ideas, and the theological idea, Kant lays out his reasons for thinking that while reason is over and over again tempted to suppose that it must be capable of knowing the truth of synthetic judgments a priori about the soul, the world, and God, this is in fact impossible�and indeed for a reason only a critique of the reason can make clear, namely, that while our use of the categories to secure knowledge of things that are objects of possible experience is a perfectly legitimate use, their employment in the service of any attempt to extend that knowledge to the soul, the world, and God is not Have the Ideas any legitimate use? Kant thinks so: they can serve, he thinks, to help us impart to our knowledge the form of a system (97), but used in any other way, they invariably give rise to illusion

20. Prolegomena, Part III With this, Kant�s Prolegomena has reached its end; the Conclusion, the Solution, and the Appendix (99-133) though interesting, add nothing essential to the main argument of the book Summing up, we can say that: unless the argument of Part I is flawed, we can now understand how it is that we can know what we know in mathematics, and similarly, unless the argument of Part II is flawed, we can now understand how it is that we can know what we know in the pure science of nature that was traditionally thought of as the part of metaphysics having to do with the nature of beings qua beings: general metaphysics; as for special metaphysics�rational psychology, rational cosmology, and rational theology�if the argument of Part III is not flawed, we can now see that no such thing shall ever be able to come forth as science; to be rational, our beliefs regarding the soul, the world, and God will have to remain mere beliefs, articles of a faith that can be grounded only in the practical use of our reason and in our awareness of the moral law