But in the popularization and wide acceptance of the natural selection dogma, we are in face of one of those familiar histories of the rise and dominance of a plausible, logically-constructed, apparently simple and sufficient explanation of a great problem pressing for solution. It is difficult for the world to accept the evolution theory without a causal explanation of it. But as the known facts prove the theory beyond reasonable doubt, it is necessary to accept it. Hence there is to most people a simultaneous necessity for accepting some explanation of it. Natural selection has had the fortune of being, since Darwin's time, the generally accepted explanation. What then is it, really? It is an explanation of evolution which it is the merit of Darwin to have devised;--or perhaps we ought already to say in the light of the fatal results brought about by the wide unreasoning acceptance of it, it is the demerit of Darwin to have devised;--an explanation based partly on certain observed facts, but more largely on a certain logical elaboration of argument for which the observed facts are assumed to be sufficient base. The more relevant of these facts are the production by parents of too many young and the slight differing of these young among themselves in most of their characters, physical and mental. The production of too many young leads, according to the natural selectionists, to a life and death struggle for existence among them, and the slight differences among them lead to a decision in this struggle on a basis of the slight advantages or disadvantages of these differences. The two logical conclusions seem to be inevitable on the basis of the two facts. On the structure so far reared, however, other blocks are placed. The selectionists believe that by the laws of heredity, although the young of a different parent or pair of parents do differ among themselves, they resemble their own parents more closely than they resemble other individuals of their kind of species. So that the young produced by the survivors in the struggle for existence, although again slightly differing from their parents and each other, will, by the laws of heredity, tend to reproduce in their make-up the advantageous variations which were possessed by their parents and which gave these parents success in the struggle for life.