Criticizing Kant's theory of knowledge exposed in the "Critique of Pure Reason" and his conception of truth – which he compares to Plato's conception of truth as its symmetrical inversion (order of nature/order of thought) – Bergson attempted to redefine the relations between science and metaphysics, intelligence and intuition, and insisted on the necessity of increasing thought's possibility through the use of intuition, which, according to him, alone approached a knowledge of the absolute and of real life, understood as pure duration. Because of his (relative) criticism of intelligence, he makes a frequent use of images and metaphors in his writings in order to avoid the use of concepts, which (he considers) fail to touch the whole of reality, being only a sort of abstract net thrown on things. For instance, he says in "The Creative Evolution" (chap. III) that thought in itself would never have thought it possible for the human being to swim, as it cannot deduce swimming from walking. For swimming to be possible, man must throw itself in water, and only then can thought consider swimming as possible. Intelligence, for Bergson, is a practical faculty rather than a pure speculative faculty, a product of evolution used by man to survive. If metaphysics is to avoid "false problems", it should not extend the abstract concepts of intelligence to pure speculation, but rather use intuition.