We need not fear that our old fundamental beliefs will be lost. Their very age shows that they have been thoroughly tested in the great experiment of human history and found sure. Modified they may be; they will be used for higher purposes and the building of better characters than ours. They will not be lost or discarded. We too often think of nature as building like man, with huge scaffoldings, which must later be torn down and destroyed. But in the forest the only scaffolding is the heart of oak.
We have seen that the sequence of functions in animal development has culminated in man's rational, moral nature. He alone has the clear perception of the reality of right, truth, and duty. The pursuit of these has made him what he is. His advance, if there is any continuity in history, depends upon his making these the ruling motives and aims of his life. He must continually grow in righteousness and unselfishness, if he is not to degenerate and give place to some other product of evolution. Moreover, as these moral faculties are capable of indefinite, if not infinite, development, they must dominate his life through a future of indefinite duration. For the length of the period of dominance of a function has always been proportional to the capacity of that function for future development. These can never, so far as we can see, be superseded, for no rival to them can be discovered. We have found in them the culmination of the sequence of functions.
We have attempted to show in this lecture that reversal of this grand sequence has always led to degeneration, or, in higher forms, far more frequently, to extinction. As we ascend, natural selection works more, rather than less, unsparingly. And as advance depends upon conformity to environment, and as the highest forms must be regarded as therefore most completely conformed, we gain our most adequate knowledge of environment when we study it as working especially for these. For these have been from the very beginning its far-off, chief aim and goal. Viewed from this standpoint, environment proves to be a host of interacting forces uniting in a resultant "power, not ourselves, that makes for righteousness," and unselfishness.