_Universality of Evolution._--Evolution as a _process_ is not confined to one thing, the egg, nor as a doctrine is it confined to one department of science--biology. The process pervades the whole universe, and the doctrine concerns alike every department of science--yea, every department of human thought. It is literally one half of all science. Therefore, its truth or falseness, its acceptance or rejection, is no trifling matter, affecting only one small corner of the thought-realm. On the contrary, it affects profoundly the foundations of philosophy, and therefore the whole domain of thought. It determines the whole attitude of the mind toward Nature and God. I have said evolution constitutes one half of all science. This may seem to some a startling proposition. I stop to make it good. Every system of correlated parts may be studied from two points of view, which give rise to two departments of science, one of which--and the greater and more complex--is evolution. The one concerns changes within the system by action and reaction between the parts, producing equilibrium and stability; the other concerns the progressive movement of the system, as a whole, to higher and higher conditions--the movement of the point of equilibrium itself, by constant slight disturbance and readjustment of parts on a higher plane, with more complex inter-relations. The one concerns the laws of sustentation of the system, the other the laws of evolution. The one concerns things as they are, the other the process by which they become so. Now, Nature as a whole is such a system of correlated parts. Every department and sub-department of Nature, whether it be the solar system or the earth, or the organic kingdom, or human society, or the human body, is such a system of correlated parts, and is therefore subject to evolution. We can best make this thought clear by examples: