REVOLT AGAINST PURE EMPIRICISM AND PURE RATIONALISM
From among the pronounced tendencies of the seventeenth and eighteenth centuries I shall select two for special emphasis. In the first place, it was characteristic of these two centuries to isolate and over-emphasize either one or the other of the two great sources of human knowledge, sense-perception or reason. Locke and his followers attempted to convert reason into a mere echo of sense; while for Descartes and his followers, sense was always viewed with suspicion as confusing the intellect, or as supplying only an inferior sort of knowledge which must yield precedence to “rational science.” Extreme sensationalism or empiricism seemed to have reached an impasse in Hume; while rationalism degenerated into formalism and word-making in Wolff. Thus Kant’s greatest work, the “Critique of Pure Reason” (1789), was an attempt to correct these extreme views by making the necessary provision for both sense-perception and reason. Perception without conception, he said, is blind; while conception without perception is empty. Kant’s critique was aimed first at excessive emphasis on sense-perception. He showed that the bare sequence of sense-impressions can never yield the connections, necessities, unities, laws, etc., which are required for science. The intellect must supply these itself. They constitute what Kant called “categories,” the instruments which the mind must use when it works in that peculiar way which is called knowing. But it follows that they are not by themselves sufficient for knowledge. They cannot themselves be known in the ordinary way because they are what one knows with. And since they are instruments, it follows that they require some material to work upon; they cannot spin knowledge out of nothing. Hence the data of sense are indispensable also. In short, to know is to systematize, by the instrumentalities native to the mind, the content conveyed by the senses. This is the Kant of the first Critique, the Kant of technical philosophy who numbers many faithful devotees among the thinkers of to-day.