surrounding nature may give a remarkable impetus to the development of science. Now this puts an entirely different construction on the facts. Assume that racial differences _are_ at the bottom of some of the observed cultural differences. This fact would not necessarily mean, then, that the _average_ ability of the inferior races is less, but only that extreme variations of an advantageous character occur less frequently among them. This, for example, is the view taken by Professor Eugen Fischer, the physical anthropologist, a very firm believer in racial differences, but as regards variability rather than in point of average intellectual equipment. It is also essentially, if I understand him, the point made by Professor Thorndike. But precisely because the population of the several races differs so enormously, we are for many of them without a fair standard of comparison. Statistically, any actual number of measurements is only a small sample of an infinite series; but we have no means of ascertaining empirically what the extreme variations of which Veddas or Australians are organically capable, would be like. This, necessarily, leaves the ultimate problem of racial differences unsolved. Nevertheless, our considerations have not been in vain. They show, for one thing, how many factors have to be weighed in arriving at a fair estimate of racial capabilities, factors which are naively ignored in most popular discussions of the subject. We can, farther, say positively that whatever differences may exist have been grossly exaggerated. In the simpler mental operations, comparative psychological studies indicate a specific unity of mankind. Differences in culture are certainly not proportionate to mental differences, _i.e._, relatively slight differences in native ability may well have produced tremendous cultural effects. Since, finally, cultural differences of enormous range occur within the same race, and even within very much smaller subdivisions, the ethnologist cannot solve his cultural problems by means of the race factor. Even if an ultimate investigation should definitely fix the cultural limits to which a given race is hereditarily subject, such information could not solve the far more specific problem why the same people a few hundred years earlier were a horde of barbarians and a few hundred years later formed a highly civilized community. The supposed explanation by racial potentialities would be far too general to interpret the actual happenings. Racial psychology, no less than general psychology, thus fails to solve the problems of culture. III. CULTURE AND ENVIRONMENT[1]