varies directly with the amount of intercommunication with him. The capacity to assimilate the interests of another individual with one’s own, to allow him, as it were, to partake in one’s own personality, is what is called altruism, and might equally well perhaps be called expansive egoism. It is a characteristic of the gregarious animal, and is a perfectly normal and necessary development in him of his instinctive inheritance.
Altruism is a quality the understanding of which has been much obscured by its being regarded from the purely human point of view. Judged from this standpoint, it has been apt to appear as a breach in the supposedly “immutable” laws of “Nature red in tooth and claw,” as a virtue breathed into man from some extra-human source, or as a weakness which must be stamped out of any race which is to be strong, expanding, and masterful. To the biologist these views are equally false, superfluous, and romantic. He is aware that altruism occurs only in a medium specifically protected from the unqualified influence of natural selection, that