Early October 2026: in Year 4 of the human sciences high school (the Italian liceo delle scienze umane) philosophy is working on Descartes, English empiricism and the Enlightenment. Kant, if the syllabus follows the usual order, comes after: between November and January, and takes up four to six weeks. So the oral test on him falls six to twelve weeks from today, not tomorrow. I am writing to you now because Kant is the author on whom you see the difference between those who have understood and those who have learned by heart, and because he can only be truly understood if you have in mind the problem he starts from: Hume. Anyone who has done the work of these months well arrives at Kant with half the road already covered.
This post is about the Critique of Pure Reason. It does not replace your textbook: it gives you the backbone from which the oral test is built.
What the oral test on Kant really asks
They almost never ask you “tell the story of the Critique”. They ask you one of these:
- “What are synthetic a priori judgements and why does Kant need them?”
- “What does Kant mean by the Copernican revolution?”
- “Why, for Kant, can metaphysics not be a science?”
- “What is the difference between phenomenon and noumenon?”
These are four ways of asking the same thing: what can we know, and what can we not. If you have the thread, the four questions become easy. Without the thread they are four separate chapters and you get lost.
The starting point: Hume’s problem
Hume leaves you holding a dilemma. All knowledge is of two kinds: relations of ideas (mathematics: certain, but it tells us nothing about the world) and matters of fact (physics, experience: it tells us about the world, but is never certain). The most serious case is causality: we never see the cause, we see one event followed by another; that “every event has a cause” would be, for Hume, only a habit of the mind.
Kant has before him Newton’s physics, which works and makes exact predictions. If Hume were right, physics would be only a habit. Kant says it cannot be, and asks himself: how is knowledge possible that is at once certain and informative about the world? From here comes the distinction that matters most in the whole oral test.
The three types of judgement
Kant classifies judgements along two axes.
- Analytic / synthetic: in an analytic judgement the predicate is already contained in the subject (it explains, but adds nothing); in a synthetic one the predicate adds something (it extends knowledge).
- A priori / a posteriori: a priori means independent of experience, hence universal and necessary; a posteriori means that it depends on experience, hence only probable.
| Judgement | Type | Why |
|---|---|---|
| “Bodies are extended” | analytic a priori | extension is already contained in the concept of body; there is no need to look at anything |
| “All bodies are heavy” | synthetic a posteriori | weight is not in the concept of body, I find it out through experience |
| “7 + 5 = 12” | synthetic a priori | the concept of 12 is not contained in “7 plus 5”: I have to construct the sum; and yet it is necessary |
| “Every event has a cause” | synthetic a priori | it does not derive from experience (which gives me only successions) but is the condition for doing science |
The first two raise no problems: they are the types Hume already knew. The third type, synthetic a priori, is Kant’s wager: judgements that extend knowledge and are at the same time necessary. Mathematics and the principles of physics are made like this. The work of the Critique is to explain how they are possible.
The Copernican revolution
The answer lies in the move that Kant himself calls the “Copernican revolution”. Until then it was thought that knowledge was the mind conforming to objects: the object is there, I mirror it. If so, I cannot know anything necessary about objects before having seen them. Kant turns it round: it is objects that conform to our capacity to know. What I know is already “formed” by the structures with which my mind grasps it, and of these structures I can know something before experience.
From here come two words to be used precisely.
- Phenomenon: the thing as it appears to us, that is, as the mind structures it. It is the only possible object of knowledge.
- Noumenon (or thing-in-itself): the thing as it is independently of our way of knowing it. We can think it, not know it.
The three parts of the Critique
Transcendental Aesthetic: space and time
It starts from sensibility. Space and time are not things in the world, they are the a priori forms of sensibility: the “filters” through which every datum of the senses reaches us. Space is the form of outer sense, time that of inner sense (and therefore, in some way, of everything we perceive as well). This explains geometry and arithmetic: they are synthetic a priori because they speak of the forms of our perceiving, which hold for every possible experience.
Transcendental Analytic: categories and the “I think”
The understanding is the faculty of thinking objects by means of concepts. The pure a priori concepts are the categories (twelve, grouped into quantity, quality, relation, modality): among them, cause-effect and substance. Without categories the material of the senses would remain chaos; without sensible intuitions the categories would be empty. The formula to know: “thoughts without content are empty, intuitions without concepts are blind”. What unifies everything is the “I think” (transcendental apperception): the unity of consciousness that accompanies every one of my representations. Here Kant answers Hume: causality is not a habit, it is a category, and therefore holds necessarily for every phenomenon.
Transcendental Dialectic: the ideas and metaphysics
Reason, however, is not content with phenomena: it wants the unconditioned. It thus produces three ideas: the soul (the unity of the subject), the world (the totality of phenomena), God (the ground of everything). The trouble is that here there is no sensible intuition to fill them: the categories, applied beyond experience, spin in a void and produce contradictions (the antinomies). That is why metaphysics as a science is impossible: not because it is false, but because it claims to know what is given in no possible experience. The ideas remain useful as a regulative horizon of enquiry, not as objects of knowledge.
The mistakes that cost the most marks
1. “Kant says that reality does not exist.” False. For Kant things exist, and the noumenon is there. What he says is that we do not know things as they are in themselves, but only as they appear to us. It is not scepticism: phenomenal knowledge is valid and necessary.
2. Confusing a priori with innate. A priori does not mean “we are born with that idea in our head” (that is Descartes’s language). It means condition of experience: logically prior, not chronologically. Space is not an idea we have as children; it is the way in which every experience is possible.
3. Mixing up the noumenon with God. The noumenon is the thing-in-itself in general, not a name for God. God is one of the three ideas of reason, and it too is not an object of knowledge. Whoever overlaps them shows that they have not separated the Critique of Pure Reason from the metaphysics that the Critique criticises.
4. A list of parts without a thread. Aesthetic, Analytic, Dialectic: if you list them without saying at each step what it adds to the question “what can I know?”, it sounds like repetition.
How to answer in three minutes
The outline I recommend is always the same: problem, solution, limit.
- The problem: Hume says causality is habit; Kant wants to save science and necessity.
- Synthetic a priori judgements: they extend knowledge and are necessary; mathematics and physics are made like this.
- The Copernican revolution: objects conform to the forms of our mind.
- The three parts: forms of sensibility, categories, ideas of reason.
- The limit: we can know only phenomena; metaphysics as a science is impossible.
If you say it without hurrying and with one example per point, it takes three minutes.
Two worked cases
Case 1: classify the judgements
A typical question: “Classify these judgements and explain why ‘every event has a cause’ is the difficult case.” Answer: the table above, plus a sentence justifying its rank. “Bodies are extended” is analytic: I justify it by looking at the concept. “All bodies are heavy” is synthetic a posteriori: I have to weigh. “7 + 5 = 12” is synthetic a priori: neither addend contains 12, I need the construction in intuition. “Every event has a cause” is the most difficult because it looks like an empirical observation, but it cannot derive from experience: experience gives me only “first A, then B”, never the must. It is a condition for having ordered experience, hence synthetic a priori.
Case 2: a guided oral outline
Exam question: “Why, according to Kant, can metaphysics not be a science?”
Answer in five sentences.
- For Kant a science requires synthetic a priori judgements, and these are possible only where the concepts of the understanding are applied to sensible intuitions.
- Traditional metaphysics speaks of soul, world and God, which are given in no intuition: they are ideas of reason, not phenomena.
- By applying the categories beyond the limits of experience, reason falls into paralogisms and antinomies: it can prove opposite theses with equal evidence.
- So metaphysics is not false: it is a claim to knowledge without a possible object, and cannot be a science like physics.
- The ideas remain nonetheless as a regulative horizon of enquiry, and for Kant they will have a role elsewhere, on the practical level.
Stop there, do not add names or chapters that were not asked for: the teacher wants to see the thread, not the list.
A step forward: practical reason
Two lines of connection, just to orient you: if pure reason has closed the road to knowledge of God and the soul, the Critique of Practical Reason reopens the question on the level of morality (the moral law, the categorical imperative). I devote another post to that part: for now it is enough to know that it exists.
Practising: what there is on the site
There is no dedicated practice test for philosophy yet: there is no quiz on Kant and I do not promise you one. The category of high-school practice tests collects maths and physics tests, so it is not useful for this topic. If you are in human sciences there is, however, the human sciences maturità practice test: it trains the second paper, which is a different thing, and does not cover Kant. For this author the best training is the five questions above, said aloud with the timer set to three minutes.
To review the neighbouring authors
Kant makes sense only inside a sequence. If you want to go back, Descartes: methodical doubt and the cogito explains the first step of modern philosophy; if you want to go forward, Hegel and the dialectic in Year 5 shows what happens when idealism takes Kant as its starting point; and the “question, answer, argument” method I use here is the same as in the post on the pre-Socratics and the arche. The general picture of the subjects is on the humanities page.
How we work in lessons
With those who come to Kant we do three things, in this order. First we restart from Hume: if the problem is not clear, the solution seems a play on words. Then we build together the table of judgements with examples of your own, not the textbook’s. Finally oral practice aloud, timed: three minutes, five sentences, no paper. In philosophy there is no trick: there is a thread to learn to hold in your hand, and it has to be tried aloud several times.
If you want to see where to restart with no commitment, the free introductory call is the simplest way: you bring your situation and we look at it. For the details, there is the pricing page.
