It would be strange, reasoning from general principles, if races which have been bred apart for thousands of years and, in some cases, have become so different physically, should remain just alike as to innate mental traits. Surely it is not in accordance with what we know of heredity to suppose that millenniums of growth and adaptation in different environments have no effect upon this most plastic part of the organism. Or why should races be presumed equal in mental and moral capacity when family stocks in the same race are so evidently unequal in these respects? The next easiest thing to accepting the apparent as true is to declare it wholly false; and so in regard to races; if you have come to see that many of the differences supposed to be racial are due to environment, you will save yourself trouble by believing that all of them are of this nature. But I cannot think that a patient consideration of the facts justifies this conclusion. However, judgments of race capacity are very open to bias, and have proved so untrustworthy in the past that it is not surprising that some students regard them as altogether illusory. Fortunately, it is seldom necessary, in dealing with practical questions, to depend upon such judgments. In practice we never have to deal with race as a separate factor, but always in intimate combination with social and historical conditions. The essential thing, for most purposes, is to understand the working of the combination as a whole. Accordingly, a race problem, as understood in practical politics and sociology, does not mean one based upon a strictly biological distinction, but one in which biological and social factors, working together, produce lasting differences sufficient to keep the groups apart. In Europe most of the cases where there is an acute race situation—as between Germans and Poles in northern Prussia, between Russians and Finns, Germans and Czechs, or English and Irish—are cases where the strictly biological difference is probably not very great; the question is mainly one of antagonistic traditions. In our own Negro problem natural differences in color and physiognomy certainly play a large part, if only by defining the race line and instigating psychological attitudes. What we have to deal with, in any case, is the total situation. It follows from the importance of environment that differences which make a race problem in Europe do not necessarily do so when the peoples in question migrate to America and undergo in common the assimilating influences of a democratic civilization. Germans and Czechs, for example, do not form hostile groups here as they do in Bohemia. America has demonstrated the impermanence of many Old World divisions, while others seem to be as persistent here as anywhere. The only conclusive test is that of experience.