The usage of all language shows that community of blood was the leading idea in forming the greater and smaller groups of mankind. Words like _phylon, genos, gens, natio, kin,_ all point to the natural family as the origin of all society. The family in the narrower sense, the children of one father in one house, grew into a more extended family, the _gens_. Such were the Alkmaionidai, the Julii, or the Scyldingas, the real or artificial descendants of a real or supposed forefather. The nature of the _gens_ has been set forth often enough. If it is a mistake to fancy that every Julius or Cornelius was the natural kinsman of every other Julius or Cornelius, it is equally a mistake to think that the _gens Julia_ or _Cornelia_ was in its origin a mere artificial association, into which the idea of natural kindred did not enter. It is indeed possible that really artificial _gentes_, groups of men of whom it might chance that none were natural kinsmen, were formed in later times after the model of the original _gentes_. Still such imitation would bear witness to the original conception of the _gens_. It would be the doctrine of adoption turned the other way; instead of a father adopting a son, a number of men would agree to adopt a common father. The family then grew into the _gens_; the union of _gentes_ formed the State, the political community, which in its first form was commonly a tribe. Then came the nation, formed of a union of tribes. Kindred, real or artificial, is the one basis on which all society and all government have grown up.