Mathematics, at least, is saved from the dissolvent scepticism of David Hume. Can all the sciences be similarly saved? Yes, if their basic principle, the law of causality—that a given cause must always be followed by a given effect—can be shown, like space and time, to be so inherent in all the processes of understanding that no future experience can be conceived that would violate or escape it. Is causality, too, à priori, an indispensable prerequisite and condition of all thought?
