The race problem has sometimes been described as a problem in assimilation. It is not always clear, however, what assimilation means. Historically the word has had two distinct significations. According to earlier usage it meant "to compare" or "to make like." According to later usage it signifies "to take up and incorporate."

There is a process that goes on in society by which individuals spontaneously acquire one another's language, characteristic attitudes, habits, and modes of behavior. There is also a process by which individuals and groups of individuals are taken over and incorporated into larger groups. Both processes have been concerned in the formation of modern nationalities. The modern Italian, Frenchman, and German is a composite of the broken fragments of several different racial groups. Interbreeding has broken up the ancient stocks, and interaction and imitation have created new national types which exhibit definite uniformities in language, manners, and formal behavior.

It has sometimes been assumed that the creation of a national type is the specific function of assimilation and that national solidarity is based upon national homogeneity and "like-mindedness." The extent and importance of the kind of homogeneity that individuals of the same nationality exhibit have been greatly exaggerated. Neither interbreeding nor interaction has created, in what the French term "nationals," a more than superficial likeness or like-mindedness. Racial differences have, to be sure, disappeared or been obscured, but individual differences remain. Individual differences, again, have been intensified by education, personal competition, and the division of labor, until individual members of cosmopolitan groups probably represent greater variations in disposition, temperament, and mental capacity than those which distinguished the more homogeneous races and peoples of an earlier civilization.

What then, precisely, is the nature of the homogeneity which characterizes cosmopolitan groups?

The growth of modern states exhibits the progressive merging of smaller, mutually exclusive, into larger and more inclusive, social groups. This result has been achieved in various ways, but it has usually been followed or accompanied by a more or less complete adoption by the members of the smaller groups of the language, technique, and mores of the larger and more inclusive ones. The immigrant readily takes over the language, manners, the social ritual, and outward forms of his adopted country. In America it has become proverbial that a Pole, Lithuanian, or Norwegian cannot be distinguished, in the second generation, from an American born of native parents.

There is no reason to assume that this assimilation of alien groups to native standards has modified to any great extent fundamental racial characteristics. It has, however, erased the external signs which formerly distinguished the members of one race from those of another.

On the other hand, the breaking up of the isolation of smaller groups has had the effect of emancipating the individual man, giving him room and freedom for the expansion and development of his individual aptitudes.

What one actually finds in cosmopolitan groups, then, is a superficial uniformity, a homogeneity in manners and fashion, associated with relatively profound differences in individual opinions, sentiments, and beliefs. This is just the reverse of what one meets among primitive peoples, where diversity in external forms, as between different groups, is accompanied by a monotonous sameness in the mental attitudes of individuals. There is a striking similarity in the sentiments and mental attitudes of peasant peoples in all parts of the world, although the external differences are often great. In the Black Forest, in Baden, Germany, almost every valley shows a different style of costume, a different type of architecture, although in each separate valley every house is like every other and the costume, as well as the religion, is for every member of each separate community absolutely after the same pattern. On the other hand, a German, Russian, or Negro peasant of the southern states, different as each is in some respects, are all very much alike in certain habitual attitudes and sentiments.

What, then, is the rôle of homogeneity and like-mindedness, such as we find them to be, in cosmopolitan states? So far as it makes each individual look like every other—no matter how different under the skin—homogeneity mobilizes the individual man. It removes the social taboo, permits the individual to move into strange groups, and thus facilitates new and adventurous contacts. In obliterating the external signs, which in secondary groups seem to be the sole basis of caste and class distinctions, it realizes, for the individual, the principle of laissez faire, laissez aller. Its ultimate economic effect is to substitute personal for racial competition, and to give free play to forces that tend to relegate every individual, irrespective of race or status, to the position he or she is best fitted to fill.

As a matter of fact, the ease and rapidity with which aliens, under existing conditions in the United States, have been able to assimilate themselves to the customs and manners of American life have enabled this country to swallow and digest every sort of normal human difference, except the purely external ones, like the color of the skin.