The unity of Spinoza’s God is further suggested by the relation of the attributes of thought and extension, however separate they must appear in their quality and causal dependence. Both are aspects of the same substance, in the one case in the form of extension, and in the other in the form of thought. In the all-inclusive nature of God, presumably each moment has an infinite number of correlative moments corresponding to the infinite number of the attributes of God. Since to human beings only two of these worlds lie in sight, only two corresponding modes appear, but always two. This correspondence of the physical and psychical throughout nature is called in later times _panpsychism_; in the relation of the body and mind of a human being it is called _psycho-physical parallelism_. This correspondence helped Spinoza to solve the apparent dualism of the two worlds. While ideas are determined only by ideas, and motions by motions, both series point below to the divine substance which is the significance of both. They are like the top and bottom sides of a piece of paper, neither side constituting the piece of paper, but both being necessary to it. The substance is immanent in thought as well as in extension. Both thought and extension are aspects of God. The relation of thought and extension through the Deity discloses the monistic character of Spinoza’s philosophy and seems to prove that he cannot be a materialist, although some critics have said that he is. The same reality is seen, now as consciousness and now as extension.