Critique of Pure Reason

Overview

Seven hundred pages, written in a hurry after eleven years of silence, published in 1781, incomprehensible to its first readers, and substantially rewritten in 1787. Both versions are printed together in modern editions, marked A and B, which is why references look like A51/B75.

The prose is genuinely bad. Kant apologises for it. Sentences run a third of a page, the technical vocabulary is invented and unexplained, and the architecture is buried under an obsessive scheme of divisions and subdivisions borrowed from the logic textbooks of his day.

The question, though, is simple to state. Some of what we know is necessary and universal: seven plus five is twelve, every event has a cause. Experience cannot deliver necessity, since it only ever reports what has happened so far, which is Hume’s point and the one that woke Kant from what he called his dogmatic slumber. Yet these claims are not merely definitional either. So how are they possible?

The argument

The answer, in one sentence: they are possible because they state the conditions of any possible experience, which the mind itself supplies.

The Transcendental Aesthetic, about forty pages and the most readable part, deals with sensibility. Space and time are not things we find in the world or relations between objects. They are the forms under which anything can be given to us at all. That is why geometry is both necessary and about the world: it describes the form every outer experience must take.

The Transcendental Analytic deals with the understanding. Kant derives twelve categories, among them substance, causality and necessity, from the forms of judgement, and then has to show that they apply to experience. This is the Transcendental Deduction, the hardest forty pages in modern philosophy, rewritten completely between editions because the first attempt failed. The argument, compressed to the point of caricature: experience is not a slideshow of disconnected impressions; for anything to count as my experience at all, its contents must be combined into one consciousness, and the categories are the rules of that combining. So they must apply to whatever can be experienced.

The Analytic of Principles then works out what follows: substance persists, every change has a cause, all substances interact. These are not discoveries about nature. They are the conditions under which anything could show up as nature.

The price is stated plainly. We know appearances, phenomena, and not things as they are in themselves. The thing in itself is not a hidden object behind the curtain; it is what we must acknowledge and cannot say anything about.

The Transcendental Dialectic, the second half, is the demolition. Reason cannot help pressing beyond experience toward three unconditioned things: the soul, the world as a totality, and God. Each attempt produces illusion. The paralogisms show that the arguments for a simple immortal soul confuse the formal unity of consciousness with a substance. The antinomies show that reason can prove both sides of four contradictions about the world, including whether it has a beginning in time and whether there is freedom. The Ideal of Pure Reason dismantles the three traditional proofs of God, and the objection to the ontological argument, that existence is not a predicate, is the one everyone remembers.

How to read it

Read the Prolegomena first. Kant wrote it in 1783 precisely because the Critique had been misunderstood, it is a fifth the length, and it lays out the same argument in the order you would explain it to someone. Anyone who tells you to start with the Critique itself is describing an ordeal, not a method.

Then read, in the Critique: both Prefaces, the Introduction, the Transcendental Aesthetic entire, and in the Dialectic the antinomies and the critique of the proofs of God. Approach the Deduction last and do not expect to master it. Most courses assign the B edition version.

Learn four terms before you start and the fog lifts considerably. A priori: independent of experience. Synthetic: the predicate adds something not contained in the subject. Transcendental: concerning the conditions of possible experience, which is not the same as transcendent, meaning beyond experience. Intuition: not a hunch but whatever is given directly to the senses.

Guyer and Wood is complete, scrupulous and the translation citations assume. Kemp Smith is freer and often clearer at the cost of precision. If you are reading alone, having both open is not excessive.

The common misreading is that Kant says the mind creates reality. He says something narrower: the mind supplies the form, and something independent of us supplies the matter. He spends a whole section, the Refutation of Idealism, distancing himself from Berkeley.

Questions it raises

• If we know only appearances, in what sense do we know the thing in itself exists at all, and is Kant entitled to say it does?
• The Deduction argues that experience must be unified to be mine. Does that establish the categories, or only that some combining happens?
• Space and time as forms of sensibility made Euclidean geometry necessary. What did non-Euclidean geometry and relativity do to that claim?
• Kant resolves the third antinomy by putting determinism in appearances and freedom in things in themselves. Does that save freedom or relocate it beyond reach?
• If the traditional proofs of God all fail, what exactly is the faith that denying knowledge makes room for?
• Kant thought he had found the fixed structure of any possible mind. How would he answer the claim that he described the structure of an eighteenth-century European one?