Biological scientists seldom find themselves writing an introduction to what is essentially a study of a social problem. However, the problem in this instance is of such great importance from both the scientific and social standpoints, and the two are so closely interrelated, that we cannot dissociate ourselves from the task. Our professional interest lies in the scientific foundations on which Mr. Putnam rests his thesis. We are in complete accord with what he has to say concerning these foundations. We agree with his balanced presentation of genetic and environmental factors in the area of both racial and individual biology. We believe they deserve this sharp reappraisal in the light of current problems in the world at large. We can also confirm Putnam's estimate of the extent to which non-scientific, ideological pressures have harassed scientists in the last thirty years, often resulting in the suppression or distortion of truth. The intrusion of political thought into the social and anthropological sciences which has occurred on a massive scale during this period, has been a very great disservice to scientific investigation and to the guidance which scientific work and its conclusions ought to be able to render to human society. Man must be guided by science, but scientific thought must not be moulded to preconceived political ideas.