McDougall is repeating what many, especially among eugenists, have previously said. While not disputing the element of truth in the facts and arguments brought forward from this side, it may be pointed out that they are often overstated. This has been well argued by Carr-Saunders in his valuable and almost monumental work, “The Population Problem,” and his opinion is the more worthy of attention as he is himself a worker in the cause of eugenics. He points out that the social ladder is, after all, hard to climb, and that it only removes a few individuals from the lower social stratum, while among those who thus climb, even though they do not sink back, regression to the mean is ever in operation so that they do not greatly enrich in the end the class they have climbed up to. Moreover, as Carr-Saunders pertinently asks, are we so sure that the qualities that mark successful climbers—self-assertion, acquisition, emulation—are highly desirable? “It may even be,” he adds, “that we might view a diminution in the average strength of some of the qualities which mark the successful at least with equanimity.” Taken altogether, it would seem that the differences between social classes may mainly be explained by environmental influences. There is, however, ground to recognise a slight intellectual superiority in the upper social class, apart from environment, and so great is the significance for civilisation of quality that even when the difference seems slight it must not be regarded as negligible.[120]