But in saying that the essence of morality is unreasoning I do not mean that it is unreasonable. All I mean is that it can receive a reasonable justification, and that no matter how lofty the development it has its basis in the fundamental conditions of associated animal and human life. We may surround the subject with a vague and attractive idealistic verbalism, but we come back to this as a starting point. The love of family, with all its attendant values, rests upon the fact of crude sexual desire, refined, of course, during the passing of many generations, but dependent upon it all the same. Remove the sexual desire and the family feelings are inexplicable. Thus, the _reason_ for the existence of the sexual instinct is race preservation, but the end has been achieved in a quite unreasoning manner. In the animal world at large there is certainly no conscious desire for the production of offspring, nor is there with the mass of human beings. There is the desire to gratify an impulse, and very little more. And for the strengthening of an instinct there need not be, nor is there, any consciousness of its social value. All that is necessary is that it shall be useful. Natural selection attends to the rest.
This will, I think, supply an answer to the contention that secular ethics can supply a "must," but not an "ought"; that is, it may show that an individual should act in accordance with his inclinations, but in cases where these clash with the social well being, it can supply no reason why the former should give way to the latter.
The argument rests upon a dual confusion. First, the moral "ought" is no more than an organised and conscious form of "must," and not something distinct from it. One may test the matter by taking a case. A man says, I ought so to work as to promote the general welfare of society. If we seek to find the source of this feeling we come ultimately upon the feeling of tribal solidarity in virtue of which certain tribes survive in the struggle for existence. It is gregariousness struggling into consciousness. The moral "ought" is an idealised form of the primitive tribal "must." And the "must" of primitive life is encouraged and developed because it is one of the conditions of survival.