If I manage to prove this proposition, I shall have given a meaning to the word “degeneration.” By showing how the essential quality of a nation gradually alters, I shift the responsibility for its decadence, which thus becomes, in a way, less shameful, for it weighs no longer on the sons, but on the nephews, then on the cousins, then on collaterals more or less removed. And when I have shown by examples that great peoples, at the moment of their death, have only a very small and insignificant share in the blood of the founders, into whose inheritance they come, I shall thereby have explained clearly enough how it is possible for civilizations to fall—the reason being that they are no longer in the same hands. At the same time I shall be touching on a problem which is much more dangerous than that which I have tried to solve in the preceding chapters. This problem is: “Are there serious and ultimate differences of value between human races; and can these differences be estimated?” I will begin at once to develop the series of arguments that touch the first point; they will indirectly settle the second also. To put my ideas into a clearer and more easily intelligible form I may compare a nation to a human body, which, according to the physiologists, is constantly renewing all its parts; the work of transformation that goes on is incessant, and after a certain number of years the body retains hardly any of its former elements. Thus, in the old man, there are no traces of the man of middle age, in the adult no traces of the youth, nor in the youth of the child; the personal identity in all these stages is kept purely by the succession of inner and outer forms, each an imperfect copy of the last. Yet I will admit one difference between a nation and a human body; in the former there is no question of the “forms” being preserved, for these are destroyed and disappear with enormous rapidity. I will take a people, or better, a tribe, at the moment when, yielding to a definite vital instinct, it provides itself with laws and begins to play a part in the world. By the mere fact of its wants and powers increasing, it inevitably finds itself in contact with other similar associations, and by war or peaceful measures succeeds in incorporating them with itself. Not all human families can reach this first step; but it is a step that every tribe must take if it is to rank one day as a nation. Even if a certain number of races, themselves perhaps not very far advanced on the ladder of civilization, have passed through this stage, we cannot properly regard this as a general rule.