Originally published in 1964, this book critically examines some philosophical theories of the relation between reason and morality, with particular reference to the writings of Cudworth, Locke, Clarke, Hume and Kant. It also discusses the ways in which conduct may be assessed or criticised, and of the extent to which these ways of assessment may amount to, or be connected with, moral assessment. The conclusion shows how far and in what ways rational moral judgment is possible and what are its inevitable limitations.