We will suppose then that a theory has been formed which professes to explain, on the method of a natural history conducted according to the principle of evolution, the process by which the human animal has come, according to the terminology in vogue, to exhibit the phenomena of a moral life—to have a conscience, to feel remorse, to pursue ideals, to be capable of education through appeals to the sense of honour and of shame, to be conscious of antagonism between the common and the private good, and even sometimes to prefer the former. It has generally been expected of a moralist, however, that he should explain not only how men do act, but how they should act: and as a matter of fact we find that those who regard the process of man’s natural development most strictly as a merely natural one are as forward as any to propound rules of living, to which they conceive that, according to their view of the influences which make him what he is, man ought to conform. The natural science of man is to them the basis of a practical art. They seek to discover what are the laws—the modes of operation of natural forces—under which we have come to be what we are, in order that they may counsel us how to seek our happiness by living according to those laws. (§7 ¶1)

Now it is obvious that to a being who is simply a result of natural forces an injunction to conform to their laws is unmeaning. It implies that there is something in him independent of those forces, which ma determine the relation in which he shall stand to them. A philosopher, then, who would reconstruct our ethical systems in conformity with the doctrines of evolution and descent, if he would be consistent, must deal less scrupulously with them than perhaps any one has yet been found to do. If he has the courage of his principles, having reduced the speculative part of them to a natural science, he must abolish the practical or preceptive part altogether. Instead, for instance, of telling men of a greatest sum of pleasures which they ought to seek, and which by acting in the light of a true insight into natural laws they may attain, he will content himself with ascertaining, so far as he can, whether such and such a temperament under such and such circumstances yields more frequent, durable, and intense pleasures than such another temperament under such other circumstances. He will not mock the misery of him who fails, nor flatter the self-complacency of him who prospers, by speaking of a happiness that is to be obtained by conformity to the laws of nature, when he knows that, according to his own principles, it is a struggle for existence determined by those laws which has brought the one to his wretchedness and the other to his contentment. He will rather set himself to show how the phraseology of ought and ought not, the belief in a good attainable by all, the consciousness of something that should be though it is not, may according to his philosophy be accounted for. Nor, if he has persuaded himself that the human consciousness, as it is, can be physically accounted for, will he find any further difficulty in thus explaining that language of moral injunction which forms so large an element in its expression. He will probably trace this language to the joint action of two factors—to the habit of submission to the commands of a physical or political superior, surviving the commands themselves and the memory of them, combined with that constant though ineffectual wish for a condition of life other than his own, which is natural to a being who looks before and after over perpetual alternations of pleasure and pain. (§7 ¶2)