racial difference between the peoples involved. If this difference is very great and the numerical relation makes the absorption of the one by the other impossible, there develops a distinction of castes, as in India, where the lower castes are clearly distinguishable from the higher, even as to physical characteristics. The situation is radically different where there is less divergence between the two populations. In such cases, racial distinctions do not occur, or at least only to a small extent; in their stead, we find differences with respect to property and power. The conquering race becomes a privileged class; those who are subjugated form a class of dependents who possess fewer rights. There is no impassable barrier between the two classes, however, as there is in the caste system. The more a fairly unitary folk-type emerges from the racial fusions, and the more other factors than descent come into prominence--such as common interest in internal order and external defence, or a remarkable personal ability on the part of individual leaders of the lower classes--the greater the tendency, on the one hand, towards the abolition of traditional differences, and, on the other, towards an increased recognition of personal achievement as the basis of social standing. Such social struggles as occurred in the history of Greece and Rome from their early days on, are particularly illuminating as regards this point, for they exhibit clearly the motives that were originally involved--motives that later everywhere become more complicated.