The philosophy of Wolff was an offshoot directly from Leibnitz, indirectly from the Cartesian school. It is hardly necessary to reiterate the remark that the revolution in thought wrought by Descartes was nothing less than a protest of the human mind against any external authority for the first principles of its belief. Two great philosophers followed out his method in an independent manner; Spinoza, who attempted to exhibit with the rigour of deduction the necessary development of the idea of substance into the various modes which it assumes; and Leibnitz,(663) who, with less attempt at formal precision of method, starting with the idea of power, endeavoured, by means of the monadic theory, which it is unnecessary here to explain, to exhibit the nature of the universe in itself, and the connexion of the world of matter and of spirit. Wolff was a disciple of Leibnitz; great as a teacher rather than an inventor, who invested the system of his master slightly modified, with the precision of form which raised it to rivalry with the perfect symmetry of Spinoza’s system. Adopting his master’s two great canons of truth, the law of contradiction as regulative of thoughts, and the law of the sufficient reason as regulative of things,(664) he attempted in his theoretic philosophy to work out a regular system on each of the great branches of metaphysic,—nature, the mind, and God; by deducing them from the abstract ideas of the human mind.(665) The true method of conducting this inquiry would be strictly an _à posteriori_ one, an analytical examination of our own consciousness, to ascertain what data the facts of the thinking mind furnish with respect to things thought of. But without any such examination Wolff, assuming in reference to these subjects the abstract ideas of the human mind as his data, proceeded to reason from them with the same confidence as the realists of the middle ages, or as mathematicians when they commence with the real intuitions of magnitude on which their science is founded. Thus his whole philosophy was form without matter; a magnificent idea, but not a fact. Yet though really baseless, it was not necessarily harmful.