is, in short, our mind which, by its operation, creates the things whose aspects only at a given moment we can know and register, whose relations only we can seek to establish by means of categories which are themselves fashioned by our mind for the practical utility of life. Verifications, registrations, and categories make up our science, which is, therefore, not an immediate and objective knowledge of reality, but its representation elaborated by us at a given moment, and so subjective, relative, and capable of transformation and variation in accordance with the evolution of the human spirit, which is in a continual process of becoming. Thence has sprung a great revolution, not only in the circle of the empirical sciences, but in that of the rational sciences as well. The latest attempts to reconstruct the mathematical and geometrical sciences on a basis utterly different from that hitherto employed, attempts which have been
