Eugenics and Society 13 Eugenics is not, as some of its devotees have perhaps unconsciously assumed, a special branch of natural science; it is a branch of social science. It is not merely human genetics. True that it aims at the improvement of the human race by means of the improvement of its genetic qualities. But any improvement of the sort can only be realized in a certain kind of social environment, so that eugenics is inevitably a particular aspect of the study of man in society. Up to the present, eugenics has concerned itself primarily with a study of the hereditary constitution, and with deductive reasoning on the effects of selection. It was rightly shocked at the intellectual excesses of the perfectionists and sentimental environmentalists, who adhered to the crudest form of Lamarckism and believed that improvements in education and social conditions would be incorporated in an easy automatic way into human nature itself and so lead to continuous and unlimited evolutionary progress. As a result, it converted the distinction between nature and nurture into a hard antithesis, and deliberately or perhaps subconsciously belittled or neglected the effects of the environment and the efforts of the social reformers -- except in so far as their real or alleged dysgenic effects might be used to point a moral or provide a horrid warning. This was natural, and perhaps necessary; but it was neither scientific nor sufficient. It was an example of an error to which I have already referred, the error of assuming that the methods of the natural sciences will serve for the social sciences. The pure natural science of genetics was able, at least during it early career, to neglect consideration of the environment. It could do this because in its experiments it can and does control the environment in order to deal solely with constitutional factors. By this means it has succeeded (and by no other means could it have succeeded) in making those spectacular discoveries about chromosomes and their doubling and halving, about the existence, number and localization of the genes or hereditary units, their mutation and its effects, which in a brief quarter-century have raised it to the position of being that branch of biology which in its method and its progress most nearly conforms to the standard set by physics. But in eugenics this is not possible. The purpose of eugenics is on the one hand to study the presence of different inherited types and traits in a population, and the fact that these can be increased or diminished in the course of generations as the result of selection, unconscious or deliberate, natural or artificial, and on the other, eventually to use the results of this study for control. Eugenics studies the selective implications of human genetic differences. However, these implications may and often indeed must differ in different environments. Since the social environment is now by far the most important part of the environment of man; and since the social environment differs from one nation to another, one class to another, and its differences are outside the control of the eugenist, he must not neglect it. Its uncontrolled variables bring the eugenist face to face with the principle of multiple causation, at work here as in all the social sciences. [italics]Need for a Study of Environment[end italics] The study of the environment is necessary for the eugenist on a number of counts. First, because he cannot equalize it experimentally, he must learn to discount its effects if he is not to mistake their pinchbeck glitter (as he would be apt to think it) for the true gold of genetic influence. If, for instance, the observed lower stature of the so-called lower classes should prove to be due to inadequate diet, it is eugenically of no significance. Secondly, because by the limited control of social conditions which is open to us already, it is often possible to alter the effect of a genetic factor. Inherited eye defects, once a grave handicap in almost every walk of life, are now, in most cases, thanks to the progress of the science of optics and the art of spectacle-making, no more than a minor inconvenience. [end]