The concept of human nature usually enters discussions of the nature and implications of the social sciences in connection with one or another form of ‘relativism’. Confronted with the enormous and apparently conflicting variety of phenomena of human life at different places and times, we are inclined to ask whether there is not something which holds these phenomena together and unifies them. Stated thus baldly this question is no doubt so vague as to approach meaninglessness; it will have to be posed in different forms — and probably answered differently – according to the particular phenomena of human life which we happen to have in mind. In this lecture I shall concentrate my attention on some questions about the relevance of sociological investigations to our understanding of ethics and about the treatment of ethics in such investigations. I shall be particularly interested in the way in which the concept of human nature enters into such discussions; and I shall devote a good deal of attention to Professor Alasdair Maclntyre's recent Short History of Ethics. It is a large merit of this book that it explicitly and invigoratingly relates the manner of its historical exposition to a distinctive philosophico-sociological standpoint concerning the nature of morality. I call this a ‘merit’ and want to stand by that characterisation even though I think that there are important confusions enshrined in Maclntyre's approach. A large part of the task which I want to set myself in this lecture is to make clear the nature and importance of these confusions.