The 1970s have seen an explosive growth in the philosophical analysis of rational behaviour, rational beliefs and rational choice. Ethics, the philosophy of action and the philosophy of the social sciences are increasingly converging towards a common set of problems, where the notion of rationality is perhaps the most important unifying element. Rawls ([1], p. 16) and Harsanyi (2], p. 10) both include justice and ethics in the broader field of rational choice theory. In the philosophy of action class="EmphasisTypeItalic ">intentionality with close — if ambiguous — ties to the notion of rationality is emerging as the central concept. And the dominating place of economics within the social sciences, being both the most highly formalized and the most important for applications, has ensured that the economic theory of rational behaviour has come under close scrutiny from philosophers of science.