The logical presuppositions of Spinoza's philosophy lie in the fundamental ideas of Descartes, which Spinoza accentuates, transforms, and adopts. Three pairs of thoughts captivate him and incite him to think them through: first, the rationalistic belief in the power of the human spirit to possess itself of the truth by pure thought, together with confidence in the omnipotence of the mathematical method; second, the concept of substance, together with the dualism of extension and thought; finally, the fundamental mechanical position, together with the impossibility of interaction between matter and spirit, held in common with the occasionalists, but reached independently of them. Whatever new elements are added (_e. g_., the transformation of the Deity from a mere aid to knowledge into its most important, nay, its only object; as, also, the enthusiastic, directly mystical devotion to the all-embracing world-ground) are of an essentially emotional nature, and to be referred less to historical influences than to the individuality of the thinker. The divergences from his predecessors, however, especially the extension of mechanism to mental phenomena and the denial of the freedom of the will, inseparable from this, result simply from the more consistent application of Cartesian principles. Spinoza is not an inventive, impulsive spirit, like Descartes and Leibnitz, but a systematic one; his strength does not lie in brilliant inspirations, but in the power of resolutely thinking a thing through; not in flashes of thought, but in strictly closed circles of thought. He develops, but with genius, and to the end. Nevertheless this consecutiveness of Spinoza, the praises of which have been unceasingly sung by generations since his day, has its limits. It holds for the unwavering development of certain principles derived from Descartes, but not with equal strictness for the inter-connection of the several lines of thought followed out separately. His very custom of developing a principle straight on to its ultimate consequences, without regard to the needs of the heart or to logical demands from other directions, make it impossible for the results of the various lines of thought to be themselves in harmony; his vertical consistency prevents horizontal consistency. If the original tendencies come into conflict (the consciously held theoretical principles into conflict with one another, or with hidden aesthetic or moral principles), either one gains the victory over the other or both insist on their claims; thus we have inconsistencies in the one case, and contradictions in the other (examples of which have been shown by Volkelt in his maiden work, _Pantheismus und Individualismus im Systeme Spinozas_, 1872). Science demands unified comprehension of the given, and seeks the smallest number of principles possible; but her concepts prove too narrow vessels for the rich plenitude of reality. He who asks from philosophy more