Critique of Pure Reason

Contents

1. Motto and Dedication 2 min 6

   The second edition opens with a motto from the preface to Bacon’s Instauratio Magna, asking readers to take the work as a common labour that ends error rather than as one more sect. Kant then dedicates the book, as he had the first edition, to Baron von Zedlitz, the Prussian minister responsible for the universities, and asks his protection.

2. Preface to the First Edition 19 min 15

   Kant opens with reason’s peculiar fate: it is driven to questions it cannot answer, and metaphysics, once queen of the sciences, has become a battlefield of dogmatists and sceptics, ending in weary indifference. He proposes a tribunal, a critique of pure reason itself, to settle what reason can know independently of experience. He claims completeness and certainty, distinguishes the objective from the subjective side of the Deduction, apologises for the lack of examples, and promises a short system of the metaphysics of nature to follow.

3. Preface to the Second Edition 47 min 22

   Logic, mathematics and physics found the secure path of science through revolutions in method; metaphysics has not. Kant proposes his own Copernican experiment: suppose that objects conform to our knowledge, not knowledge to objects. This explains a priori knowledge but confines it to appearances, leaving things in themselves unknown, which in turn makes room for freedom, God and immortality as matters of practical reason: he denies knowledge to make room for faith. Kant presents criticism as a protection for morality and religion, praises Wolff’s rigour, and lists the changes made for the 1787 edition.

4. Introduction 45 min 60

   All knowledge begins with experience, but not all arises from it. Kant defines a priori knowledge by necessity and strict universality, and distinguishes analytic judgments, which unpack a concept, from synthetic ones, which add to it. Mathematics, the principles of physics and metaphysics all claim synthetic a priori truths, so the general problem of pure reason is how such judgments are possible. Hume came closest to this problem but confined it to causality. Kant then defines transcendental knowledge, calls his work a critique rather than a system, and names the two stems of knowledge, sensibility and understanding.

5. I.1 Transcendental Aesthetic 1 h 1 min 60

   Kant isolates sensibility, our capacity to receive representations, and finds two pure forms of intuition, space and time. Neither is drawn from experience; each is a single, infinite whole given a priori, and they explain the necessity of geometry and of the doctrine of motion. Space and time are empirically real but transcendentally ideal: valid for everything we can experience, nothing in things in themselves, which remain unknown. Kant answers the objection that change proves time real, rejects both Newtonian and Leibnizian theories, denies that his view reduces bodies to illusion, and contrasts our derivative intuition with an original, divine one.

6. I.2 Transcendental Logic: Introduction 22 min 9

   Knowledge requires both intuitions and concepts: thoughts without content are empty, intuitions without concepts blind. Kant separates general logic, which abstracts from all content, from a transcendental logic of the concepts that relate a priori to objects. Logic can supply only a formal, negative criterion of truth; used as an instrument for producing knowledge, it becomes dialectic, a logic of illusion. Transcendental logic therefore divides into an Analytic, a logic of truth, and a Dialectic, a critique of the illusion that arises when the understanding is used beyond experience.

7. I.2.1 Analytic of Concepts: The Clue to the Discovery of All Pure Concepts of the Understanding 40 min 19

   Kant seeks a single principle for finding all the pure concepts of the understanding. Since to think is to judge, he lists the logical forms of judgment in a table of twelve under quantity, quality, relation and modality. The same function that unifies a judgment also unifies the manifold of intuition into an object, so each form of judgment yields a category: twelve in all, unlike Aristotle’s rhapsodic list. Kant notes the mathematical and dynamical groups, the triadic pattern in each class, and reinterprets the scholastic transcendentals, one, true and good, as logical criteria.

8. I.2.1 The Deduction of the Pure Concepts of Understanding: Principles of Any Transcendental Deduction 20 min 22

   Kant borrows the jurists' distinction between a question of fact and a question of right. An empirical account of how we acquired concepts, like Locke's, cannot show that we are entitled to apply pure concepts to objects; only a transcendental deduction can. Space and time posed no special difficulty, but the categories do, since appearances might in principle fail to fit the understanding's rules. The way forward is to show that the categories are conditions of the possibility of experience. Locke led to enthusiasm, Hume to scepticism; Kant seeks a safe course between them.

9. I.2.1 Transcendental Deduction of the Categories (First Edition) 52 min 27

   The 1781 version of the Deduction, later replaced. Kant analyses knowing into a threefold synthesis: apprehension in intuition, reproduction in imagination and recognition in a concept. The object of knowledge turns out to be the rule-governed unity of our representations, an “x” grounded in transcendental apperception, the identical self-consciousness that empirical introspection never finds. Through the productive imagination this unity gives appearances their affinity and makes the understanding “the lawgiver of nature.” The summary argues that this deduction works only because objects are appearances, not things in themselves.

10. I.2.1 Transcendental Deduction of the Categories (Second Edition) 56 min 27

    The 1787 restatement. All combination is an act of the understanding, grounded in the synthetic unity of apperception: the “I think” must be able to accompany all my representations. Judgment is the act that brings representations to this objective unity, and the categories are the functions of judgment, so every unified intuition stands under them. Kant explains the figurative synthesis of imagination, why we know even ourselves only as appearance, and how categories prescribe laws to nature. The outcome: no a priori knowledge except of objects of possible experience, explained as an “epigenesis” of pure reason.

11. I.2.1 Analytic of Principles: Transcendental Judgment and the Schematism 26 min 19

    The Analytic of Principles is a doctrine of judgment, the untaught talent of applying rules to cases. Since categories are heterogeneous with sensible intuition, a mediating “third thing” is needed: the transcendental schema, a rule-governed determination of time produced by imagination. Schemata differ from images, as the method of counting differs from five dots. Kant lists the schema of each category, from number and degree to permanence, regular succession and existence at all times, and concludes that schemata both give the categories meaning and restrict them to appearances.

12. I.2.1 System of All Principles of Pure Understanding: Axioms and Anticipations 48 min 29

    Kant sets out the principles that the schematised categories yield. The principle of contradiction is the highest principle of analytic judgments; the highest principle of synthetic judgments is that every object stands under the conditions of possible experience. The principles fall into mathematical and dynamical groups. The Axioms of Intuition hold that all appearances are extensive magnitudes, which secures the application of geometry. The Anticipations of Perception hold that everything real in sensation has a degree, so experience can never prove empty space.

13. I.2.1 Analogies of Experience 1 h 14 min 53

    Kant’s three principles for connecting appearances in time, matching the categories of relation. Because time itself cannot be perceived, the objective order of things must be fixed by rules. The First Analogy holds that substance is permanent and its quantity in nature unchanged. The Second, his answer to Hume, argues that we can tell an event from a mere sequence of perceptions, the ship drifting downstream from the house surveyed at will, only if every alteration follows its antecedent by a causal rule. The Third makes universal interaction the condition of knowing that things coexist.

14. I.2.1 Postulates of Empirical Thought; Refutation of Idealism 43 min 24

    The principles of modality define possibility, actuality and necessity in terms of experience: fitting its forms, connecting with sensation, and following from the actual by causal law. Logical consistency is not enough for real possibility, and existence adds nothing to a concept. The second edition inserts the Refutation of Idealism, which argues that consciousness of my own existence in time requires something permanent outside me. It also adds a General Note showing that the categories gain content only from outer intuition. Along the way Kant states the maxims of no gap, leap, chance or fate.

15. I.2.1 Phenomena and Noumena 33 min 37

    Before entering the Dialectic, Kant surveys the “island of truth” mapped by the Analytic. Concepts and principles of the understanding have meaning only when applied to appearances, never to things in general, so the old ontology must yield to a modest analytic of the understanding. Things in themselves, or noumena, can be thought but not known. Since we lack intellectual intuition, the noumenon is admissible only in a negative sense, as a limiting concept that marks the boundary of sensible knowledge without opening a second world.

16. I.2.1 The Amphiboly of Concepts of Reflection 51 min 24

    An appendix on the four pairs of concepts used in comparing things: identity and difference, agreement and opposition, inner and outer, matter and form. Their meaning depends on whether the things belong to sensibility or to pure understanding, and neglecting this “transcendental reflection” breeds error. Kant uses the scheme to diagnose Leibniz, who “intellectualised” appearances, yielding the identity of indiscernibles, monads, pre-established harmony and relational space. Locke made the opposite mistake. The chapter ends with a fourfold table of “nothing.”

17. I.2.2 Transcendental Dialectic: Introduction 26 min 11

    The opening of the Transcendental Dialectic, the “logic of illusion.” Error arises only in judgment, and transcendental illusion, unlike logical fallacy, persists after it is exposed because it springs from reason itself. Reason, the faculty of principles, seeks to unify the understanding’s rules, and in its logical use always looks for the condition of a condition. Taken as a claim about objects, that whenever the conditioned is given the whole unconditioned series is given, this becomes the source of the transcendent ideas and syllogisms examined in the rest of the Dialectic.

18. I.2.2 The Concepts of Pure Reason 44 min 21

    Book I of the Transcendental Dialectic introduces the concepts of pure reason, which Kant calls transcendental ideas. Reclaiming the word “idea” from Plato, he defends the Republic as a necessary standard rather than an idle dream, and ranks the kinds of representation from sensation to idea. Reason, the faculty of inference, seeks for every conditioned thing the totality of its conditions, the unconditioned. The three forms of syllogism yield three ideas: the absolute unity of the thinking subject, of the series of conditions of appearances, and of the condition of all objects of thought — the topics of rational psychology, cosmology and theology.

19. I.2.2 The Paralogisms of Pure Reason (First Edition) 1 h 42 min 38

    Book II opens by naming reason's three dialectical inferences, then examines the first: the paralogisms of rational psychology, in the 1781 text. From the bare “I think” the school metaphysicians inferred that the soul is a substance, simple, a person identical over time, and certain of its own existence while the outer world is doubtful. Kant shows each inference confuses the logical unity of thought with knowledge of a thing. Against the fourth he sets out transcendental idealism and empirical realism, then argues that the debates over soul–body interaction, birth and death rest on treating appearances as things in themselves.

20. I.2.2 The Paralogisms of Pure Reason (Second Edition) 35 min 17

    The 1787 restatement of the paralogisms. Kant shows that the propositions of rational psychology — that I am subject, single, identical and distinct from outer things — are analytic truths about thought, not knowledge of a soul. A priori proof that thinking beings are simple substances would refute the whole Critique. He refutes Mendelssohn's proof of immortality by appeal to intensive magnitude, rejects both materialism and spiritualism, and keeps belief in a future life on moral grounds. A closing note points to the moral law as revealing our spontaneity, without restoring speculative knowledge of the self.

21. I.2.2 The Antinomy of Pure Reason: Cosmological Ideas and the Four Conflicts 1 h 20 min 24

    The second dialectical inference concerns the world as a whole. Kant derives four cosmological ideas from the categories, then sets out the four antinomies, each with thesis, antithesis, proofs and observations: the world has or lacks a beginning and limits; substances are or are not made of simple parts; there is freedom besides natural causality, or only nature; a necessary being belongs to the world, or none exists. Each proof is indirect and seemingly cogent. Kant presents this “sceptical method” as a way of finding the hidden assumption behind a conflict that reason cannot avoid.

22. I.2.2 The Antinomy of Pure Reason: The Interest of Reason, and Transcendental Idealism as the Key 52 min 19

    Kant steps back from the four antinomies to ask what is at stake. The theses (“dogmatism”) serve morals, religion and reason’s wish for a complete system, and are popular. The antitheses (“empiricism”) serve natural science but seem to undermine morality. Kant then argues that transcendental philosophy must be able to answer these questions, since they arise from its own ideas. A sceptical test shows that every answer is either too large or too small for possible experience. The key to the solution is transcendental idealism: objects in space and time are appearances, real within experience, and the world as a whole is never given as an object.

23. I.2.2 The Antinomy of Pure Reason: Critical Solution of the Cosmological Conflict 1 h 46 min 25

    Kant’s solution of the antinomies. The cosmological argument confuses things in themselves, whose conditions are all given at once, with appearances, whose conditions are given only in a successive regress. In the two mathematical antinomies both sides are therefore false: the world is neither finite nor infinite in itself, and bodies are endlessly divisible without consisting of infinitely many parts. The demand for totality survives only as a regulative rule of inquiry. In the dynamical antinomies both sides may be true: an act can be wholly caused as appearance and yet free in its intelligible character, and a necessary being may exist outside a world in which everything is contingent.

24. I.2.2 The Ideal of Pure Reason; the Ontological Proof 56 min 19

    Kant turns to the idea of God. To think any thing as completely determined, reason presupposes the sum of all possible realities. It then makes this sum into a single being, the ens realissimum or most real being, and calls it God. Kant traces the natural path of belief from contingent existence to a necessary and supremely real being, and names the three possible proofs: physico-theological, cosmological and ontological. He then refutes the ontological proof. Existence is not a real predicate: a hundred real thalers contain no more than a hundred possible ones, and the existence of anything can be known only from experience.

25. I.2.2 The Cosmological and Physico-theological Proofs; Critique of All Speculative Theology 1 h 4 min 19

    Kant argues that the cosmological proof, from the existence of anything to a necessary being, relies on the ontological proof to identify that being with God, and hides “a whole nest” of dialectical assumptions. Reason’s need for a necessary being is real but can only serve as a regulative idea. The physico-theological proof from design deserves respect, but it yields at most an architect of the world and must also fall back on the other two proofs. Speculative theology is therefore impossible. God can be neither proved nor disproved, and Kant points ahead to a moral theology grounded in practical reason.

26. I.2.2 Appendix to the Dialectic: The Regulative Employment of the Ideas 45 min 18

    The Appendix to the Transcendental Dialectic asks what good the ideas of reason do, once the Dialectic has shown they give no knowledge. Kant answers that they are regulative, not constitutive: they direct the understanding towards a complete, systematic unity it never reaches, like a virtual focus behind a mirror. He sets out three maxims of inquiry, homogeneity, specification and continuity of forms, illustrated from chemistry, astronomy and natural history. Read as claims about nature, the maxims conflict; read as maxims serving one interest of reason, they limit one another and guide research.

27. I.2.2 The Final Purpose of the Natural Dialectic of Human Reason 56 min 15

    Kant completes the Dialectic by giving the ideas of soul, world and God a deduction of a weaker kind: they are justified because thinking “as if” their objects existed leads to systematic unity in empirical knowledge. God may be assumed relatively, as the ground of nature’s purposive order, but never known in itself. Treated constitutively, the ideas produce lazy reason, which stops inquiry with a supernatural explanation, and perverted reason, which imposes imagined ends on nature. Properly used, pure reason yields only regulative principles.

28. II.1 Doctrine of Method: The Discipline of Pure Reason in its Dogmatic Employment 50 min 16

    The Doctrine of Method begins: having surveyed the materials of knowledge, Kant now draws up the plan, starting with a negative “discipline” for reason. Its first section asks whether philosophy can copy the method of mathematics. Kant argues it cannot. Mathematics constructs its concepts in pure intuition and so has definitions, axioms and demonstrations; philosophy reasons from concepts alone and has none of the three. Its synthetic principles, like causality, are proved only through their relation to possible experience. Dogmatic, mathematics-style method only conceals philosophy’s errors.

29. II.1 The Discipline of Pure Reason in respect of its Polemical Employment 50 min 23

    Kant defends complete freedom of criticism: reason’s authority is the agreement of free citizens. Since no one can prove either God and immortality or their denial, critics such as Hume and Priestley should be answered, not suppressed, and the young should meet their arguments armed with critique. Critique is the tribunal that ends reason’s state of nature. A closing subsection rejects scepticism as a final resting-place: Hume rightly attacked dogmatism but, failing to determine reason’s limits from principles, wrongly made causal necessity a matter of custom.

30. II.1 The Discipline of Pure Reason in regard to Hypotheses and Proofs 42 min 15

    The last two sections of the Discipline of Pure Reason set rules for hypotheses and proofs. An hypothesis is allowed only if what it supposes is possible in experience and it explains what is given; appeals to God or a simple soul as explanations are “lazy reason”. Such hypotheses may still be used defensively, to show that the materialist knows no more than the believer. Transcendental proofs must first justify their principle by showing it makes experience possible. Each such proposition has only one proof, and indirect proof by refuting the opposite is forbidden, since both sides may share a false assumption.

31. II.2 The Canon of Pure Reason 58 min 24

    Speculative reason has no canon, only a discipline; its legitimate positive use is practical. Its ultimate concerns (freedom, immortality, God) matter only for morality. Kant asks what one can know, what one ought to do and what one may hope. The moral law commands us to be worthy of happiness; since nature does not proportion happiness to worth, reason must postulate a wise Author and a future life. A final section distinguishes opinion, belief and knowledge, illustrated by betting, and concludes that belief in God and a future life is a moral certainty, not knowledge.

32. II.3 The Architectonic of Pure Reason 32 min 12

    Kant defines a science as a system organised by one idea, growing from within like an organism, not an aggregate. Philosophy cannot be learned, only practised: “we can at most learn to philosophise.” In its worldly sense philosophy concerns the essential ends of reason, chief among them morality. Kant maps pure philosophy into criticism and metaphysics, the latter of nature and of morals, and the metaphysics of nature into ontology, rational physiology, cosmology and theology. Empirical psychology is relegated to anthropology. Metaphysics, curbing reason’s excesses, remains indispensable and will always be returned to.

33. II.4 The History of Pure Reason 7 min 8

    A brief closing sketch leaves the history of pure reason to future workers. Metaphysics began with theology and morals. Its revolutions turned on three issues: the object of knowledge (sensualists like Epicurus against intellectualists like Plato), its origin (empiricists like Aristotle and Locke against noologists like Plato and Leibniz), and method (the naturalist appeal to common sense against science, which is either dogmatic like Wolff’s or sceptical like Hume’s). Only the critical path remains open, and Kant hopes to complete it before the century’s end.