In every treatise upon Christian ethics and "natural theology," so called, you will find these rules of "natural morality" in the first chapter. Thomas Aquinas called them "the eternal law." Even the Greeks and Romans, for all their skepticism in morals, had a sneaking belief in them. Aristotle tried to formulate them and the Latin lawyers constantly assumed their existence. Most of them are held in firm faith today by all save a small minority of the folk of Christendom. The most familiar of them, perhaps, is the rule against murder--the sixth commandment. Another is the rule against the violation of property in goods, wives and cattle--the eighth and tenth commandments. A third is the rule upon which the solidity of the family is based, and with it the solidity of the tribe--the fifth commandment. The theory behind these rules is, not only that they are wise, but that they are innate and sempiternal, that every truly enlightened man recognizes their validity intuitively, and is conscious of sin when he breaks them. To them Christianity added an eleventh commandment, a sort of infinite extension of the fifth, "that ye love one another"[5]--and in two thousand years it has been converted from a novelty into a universality. That is to say, its point of definite origin has been lost sight of, and it has been moved over into the group of "natural virtues," of "eternal laws." When Christ first voiced it, in his discourse at the Last Supper, it was so far from general acceptance that he named a belief in it as one of the distinguishing marks of his disciples, but now our moralists tell us that it is in the blood of all of us, and that we couldn't repudiate it if we would. Brotherhood, indeed, is the very soul of Christianity, and the only effort of the pious today is to raise it from a universal theory to a universal fact.