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These are important objections. Can they be met? In the broadest way they can and must be met by the only possible method, the method of Science, which consists in examining facts objectively, and by drawing conclusions not a priori, but a posteriori. A law of Nature is not (and I wonder how often this fallacy has been exploded, only to reappear next day)—a law of Nature is not something revealed, not something absolute, not something imposed on phenomena from without or from above; it is no more and no less than a summing-up, in generalized form, of our own observations of phenomena; it is an epitome of fact from which we can draw several conclusions. By beginning in this way from the very beginning, by examining the basis of our mode of thinking in natural science, only thus are we enabled to see at one and the same moment how to investigate the question of progress on the constructive side, and how to neutralize the force of the objections to the idea.

Questions of fact are simple to deal with. It is indubitable that some forms of life remain stationary and unevolving for secular periods; it is equally indubitable that degeneration is widespread in evolution. These are facts. But we are not therefore called upon to deny the possibility of progress. To do so would be to fall into the error of reasoning which we have already condemned. It remains for us to take these facts into account when examining the totality of facts concerning organic life, and to see whether, in spite of them, we cannot discover a series of other facts, a movement in phenomena, which may still legitimately be called progress. To deny progress because of degeneration is really no more legitimate than to assert that, because each wave runs back after it has broken, therefore the tide can never rise.