Summary: Critique of Pure Reason (page 3)

Kant provides two examples: mathematical judgements (consider the well-known law two parallel lines never intersect) and principles such as every change must have a cause¹.

Change, as an effect, is necessarily linked to the notion of cause; and the relation of causality (cause and effect) is one of our categories, or pure concepts of the understanding.

The opposite of necessary is contingent. Empirical or a posteriori judgements are contingent (their opposite is possible), whereas a priori or pure judgements are necessary.

Where does this necessity come from?

It arises precisely from the fact that these a priori concepts constitute the form of the understanding. We are therefore compelled to use them in order to think.

Let us return to our metaphor: if we put on pink-tinted glasses, we will see the world in pink. It is impossible for us not to see it in pink. The colour pink thus becomes a necessary constituent of the world as we perceive it. Similarly, the a priori concepts of our understanding are necessarily applied to our experience of the world, and the a priori judgements based on them are necessary.

We will return to this crucial point later. Grasping it is a major step towards understanding the Critique of Pure Reason.

For now, let us retain the idea—still to be fully explained and justified—that a priori judgements are necessary and universal, in contrast to empirical judgements.

At this point, it would be a mistake to continue reading the Introduction. We are now equipped to read and understand the Preface—or rather, the two Prefaces—of the work. Once this is done, we can return to the Introduction and continue reading it.

Let us take a step back and open the first Preface.

The project of the Critique of Pure Reason is contained within its title. It is therefore crucial to understand its meaning: why such a title?

Kant examines the classical epistemological question: What can we know? Or, put differently: Can we attain truth?

Kant believes that there is an intermediate position between scepticism (we can know nothing) and dogmatism (our knowledge of things is real—an idea that the dogmatist fails to prove and which therefore remains an unfounded dogma).

This intermediate position is that our knowledge is limited: within this limit, our knowledge is secure and well-founded. Beyond it, knowledge is impossible.

In other words, certain disciplines represent real and certain knowledge, while others will forever remain speculative, as their conclusions can never be definitively proven. What is needed is a clear distinction between these two kinds of disciplines—to understand why some belong to the realm of science, while others belong to mere belief or opinion.

What, then, are these two kinds of disciplines?

Some theories can be verified through experience. For instance, I can verify the theory that “this stone, once released, will fall” simply by performing the experiment. Such a theory is said to be empirically confirmed.

By contrast, some theories go beyond what experience can teach us because they concern things that are not part of our physical world. For example: Does God exist? or Is there life after death? I could only know the answer by dying—that is, by leaving this physical world. As long as I am alive, I will have no way of answering these questions, which transcend all possible experience within this world.

In other words, these are metaphysical questions (meta- meaning beyond, outside, or above). They go beyond the experience of our physical world and can never be grounded in it.

Once this is understood, we are in a better position to grasp Kant’s thesis: unlike other disciplines, metaphysics can never constitute true knowledge. It is merely a set of speculations that can never be experimentally verified and therefore belongs to the realm of belief. We thus arrive at a clear distinction between science and metaphysics.

¹ Our translation. The references for the quotations are available in the book Kant: A Close Reading