Kant: A Very Short Introduction (Very Short Introductions)

In order to introduce this novel conception of objectivity (to which he gave the name ‘transcendental idealism’) Kant began from an exploration of a priori knowledge. Among true propositions, some are true independently of experience, and remain true however experience varies: these are the a priori truths. Others owe their truth to experience, and might have been false had experience been different: these are the a posteriori truths. (The terminology here was not invented by Kant, although it owes its popularity to Kant’s frequent use of it.) Kant argued that a priori truths are of two kinds, which he called ‘analytic’ and ‘synthetic’ (A. 6-10). An analytic truth is one like ‘All bachelors are unmarried’ whose truth is guaranteed by the meaning, and discovered through the analysis, of the terms used to express it. A synthetic truth is one whose truth is not so derived but that, as Kant puts it, affirms something in the predicate that is not already contained in the subject. It is a truth like ‘All bachelors are unfulfilled’, which (supposing it to be true) says something substantial about bachelors and does not merely reiterate the definition of the term used to refer to them.

Nevertheless, it is impossible to know the world ‘as it is in itself’, independent of all perspective. Such an absolute conception of the object of knowledge is senseless, Kant argues, since it can be given only by employing concepts from which every element of meaning has been refined away. While I can know the world independently of my point of view on it, what I know (the world of ‘appearance’) bears the indelible marks of that point of view. Objects do not depend for their existence upon my perceiving them; but their nature is determined by the fact that they can be perceived.

Neither experience nor reason is alone able to provide knowledge. The first provides content without form, the second form without content. Only in their synthesis is knowledge possible; hence there is no knowledge that does not bear the marks of reason and of experience together. Such knowledge is, however, genuine and objective. It transcends the point of view of the person who possesses it, and makes legitimate claims about an independent world.

Hume’s vision is in some measure the opposite of Leibniz’s. He denies the possibility of knowledge through reason, since reason cannot operate without ideas, and ideas are acquired only through the senses. The content of every thought must be given, in the last analysis, in terms of the experiences that warrant it, and no belief can be established as true except by reference to the sensory ‘impressions’ that provide its guarantee.

Leibniz believed that the understanding contains within itself certain innate principles, which it knows intuitively to be true, and which form the axioms from which a complete description of the world can be derived. These principles are necessarily true, and do not depend upon experience for their confirmation. Hence they lead to a description of the world as it is, not as it appears in experience or to a circumscribed ‘point of view’.

Whatever the world contains, it contains the thinking being who I am. Kant’s contemporary Lichtenberg pointed out that Descartes ought not to have drawn this conclusion. The ‘cogito’ shows that there is a thought, but not that there is an ‘I’ who thinks it.

The Metaphysics of Morals, he also described the married state as an agreement between two people for the ‘reciprocal use of each other’s sexual organs’ (C.

This argument occurs, in more rhetorical form, in the writings of Sartre, whose existentialist doctrine of the moral life owes much to Kant.

and my will is the originator of nothing in the natural world

I can identify experience as mine only if I locate it in time. I must therefore ascribe it to a subject who exists in time and endures through time. My unity requires my continuity. But to endure is to be substantial, and nothing can be substantial unless it also enters into causal relations. I endure only if my past explains my future. Otherwise there is no difference between genuine duration and an infinite sequence of momentary selves. If I can be conscious of my experience at all, I can therefore conclude that I belong to a world to which such categories as substance and cause are correctly applied, since they are correctly applied to me. A condition of self-consciousness is, therefore, the existence of just that objective order which my experience suggests to me.