To sum up, we may say that the crude application to human affairs of the doctrine of the struggle for existence, torn from its biological context, isolated and over-emphasized, is wholly unwarranted. On the other hand, a struggle does continue, both of the direct and indirect type defined by Darwin: and there is no prospect of it ceasing to play an important part in human biology. Co-operation is not, any more than competition, to be taken as the sole desirable principle. Panaceas of this sort do not exist, except to make bubble reputations and quack fortunes. Even within such a highly organized co-operative unit as the mammalian body a struggle continues--the different tissues are in competition with each other for food, and if the available supply diminishes below the necessary level, some tissues will be drawn upon by other more successful competitors, and the struggle will lead to an end-result in which the proportion of the various kinds of cells comes to be very different from what they were in the normal well-nourished body.[24] That is a purely biological example. In man, since the unification of the community is of a low order, it is inevitable that individuals and sections will continue in some form of competition with each other: not only this, however, but the additional fact that man’s mental organization reacts strongly to the stimulus of competition make it probable that a “struggle” of some sort will not only be inevitable but up to a point beneficial in any form of society. What is more, once co-operation exists, competition between the co-operative units is necessary to bring out the full efficiency of their combination. All that the biologist can do is to point out that neither the one-sided application of the principle of struggle nor of that of co-operation is biologically sound. But, as everywhere else in human conduct, after the broad principles have been grasped, success lies always in a delicate, continuous adjustment of conflicting claims, in what one may call a personal conscious effort. Struggle is universal: but by itself it can only lead to a certain stage of evolutionary progress. The half-baked moralist may lay down the law about right and wrong with the most positive assurance; but, by not paying attention to the necessity for sweet reasonableness, give-and-take, unselfishness, for thought about the thousand and one details of daily conduct, he may be making himself and his wife thoroughly unhappy, ruining his family’s chances, and, as a matter of fact, be thoroughly immoral without once suspecting it. It is in a very similar way that the militarist, for instance, fortifying himself in the doctrine of the struggle for existence with what he regards as an impregnable sanction for his theories, is in reality acting immorally because not attempting to envisage the whole problem.