We have now reached a point of divergence in the development of philosophy. Descartes had affirmed and attempted to mediate the opposition, between thought and being, mind and matter. This mediation, however, was hardly successful, for the two sides of the opposition he had fixed in their widest separation, when he posited them as two substances or powers, which reciprocally negated each other. The followers of Descartes sought a more satisfactory mediation, but the theories to which they saw themselves driven, only indicated the more clearly that the whole premise from which they started must be given up. At length Spinoza abandoned the false notion, and took away its substantiality from each of the two opposed principles. Mind and matter, thought and extension, are now one in the infinite substance. Yet they are not one in themselves, which would be the only true unity of the two. That they are one in the substance is of little avail, since they are indifferent to the substance, and are not immanent distinctions in it. Thus even with Spinoza the two remain strictly separate. The ground of this isolation we find in the fact that Spinoza himself did not sufficiently renounce the Cartesian notion, and thus could not escape the Cartesian dualism. With him, as with Descartes, thought is only thought, and extension only extension, and in such an apprehension of the two, the one necessarily excludes the other. If we would find an inner mediation for the two, we must cease to abstract every thing essential from each. The opposite sides must be mediated even in their strictest opposition. To do this, two ways alone were possible. A position could be taken either on the material or on the ideal side, and the attempt made to explain the ideal under the material, or the material under the ideal, comprehending one through the other. Both these attempts were in fact made, and at about the same time. The two parallel courses of a one-sided idealism, and a one-sided realism (Empiricism, Sensualism, Materialism), now begin their development.