Any animal whatever, endowed with well-marked social instincts . . . would inevitably acquire a moral sense of conscience, as soon as its intellectual powers had become as well, or nearly as well developed, as in man. . . . A moral being is one who is capable of reflecting on his past actions and their motives—of approving of some and disapproving of others, and the fact that man is the one being who certainly deserves this designation, is the greatest of all distinctions between him and the lower animals.