We have now described the entire scale of evolution. Looking back upon it, we can see its inner significance. The Absolute is reason, matterless form. Everything in the world, therefore, is, in its essence, reason. If we wish to know the essential nature even of this clod of earth, the answer is that it is reason, although this view is not consistently developed by Aristotle, since he allows that matter is a separate principle which cannot be reduced to form. The whole universal process of things is nothing but the struggle of reason to express itself, to actualize itself, to become existent in the world. This it definitely does, for the first time proximately in man, and completely in the stars. It can only express itself in lower beings as sensation (animals), as nutrition (plants), or as gravitation and its opposite (inorganic matter). The value of Aristotle's theory of evolution is immense. It is not the details that signify. The application of the principle in the world of matter and life could not be carried out satisfactorily in the then state of physical science. It could not be carried out with perfection even now. Omniscience alone could give finality to such a scheme. But it is the principle itself which matters. And that it is one of the most valuable conceptions in {308} philosophy will perhaps be more evident if we compare it, firstly, with modern scientific theories of evolution and secondly, with certain aspects of Hindu pantheism. What has Aristotle in common with such a writer a Herbert Spencer? According to Spencer, evolution is a movement from the indefinite, incoherent, and homogeneous, to the definite, coherent, and heterogeneous. Aristotle has all this, though his words are different. He calls it a movement from matter to form. Form he describes as whatever gives definiteness to a thing. Matter is the indefinite substrate, form gives it definiteness. Hence for him too the higher being is more definite because it has more form. That matter is the homogeneous, form the heterogeneous, follows from this. We saw that there are in matter itself no differences, because there are no qualities. And this is the same as saying it is homogeneous. Heterogeneity, that is, differentiation, is introduced by form. Coherence is the same thing as organization. Aristotle has himself defined the form of a thing as its organization. For him, as for Spencer, the higher being is simply that which is more organized. Every theory of evolution depends fundamentally upon the idea of organism. Aristotle invented the idea and the word. Spencer carried it no further, though the more advanced physical knowledge of his day enabled him to illustrate it more copiously.