Page:The Harvard Classics Vol. 51; Lectures.djvu/164

 154 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.

A second and more general tendency of seventeenth and eighteenth century philosophy was its comparative neglect of what are vaguely called the "spiritual" demands. These centuries themselves may be regarded as a reaction against what was thought to be the excessive anthropomorphism of earlier times. Man had erred by reading himself into his world; now he was to view it impersonally and dispassionately. He might prefer to record the findings of perception, or the necessities of reason, but in either case he was to repress his own interests and yearnings. Of course at the time it was confidently expected that morality and religion would in this way be served best. Men believed in the possibility of a "natural religion," without mystery or dogma, a rational morality without authority, and a demonstrable theology without either revelation or faith. But gradually there developed a sense of failure. Man had left himself too much out of it, and felt homeless and unprotected. Early in the seventeenth century Pascal had announced the religious bankruptcy of the mathematical rationalism of Descartes. Natural religion was readily converted into atheism by Hume. The most vigorous and stirring protest against the whole spirit of the age was made by Rousseau, who urged men to trust their feelings, make allowance for the claims of the heart, and return to the elemental and spontaneous in human nature. The same note was caught up by