This major work in the history of ethics provides the first study of early modern British ethics in several decades. It aims to uncover the roots of the idea (called internalism in contemporary discussion) that any binding 'ought' must be based in the motives of a deliberating agent, as this notion developed in the thought of British philosophers writing in the period from Hobbes to the appearance of Hume's Treatise in 1740.

Stephen Darwall discerns two different traditions within which this idea was worked out. On the one hand, an empirical naturalist tradition, comprising Hobbes, Locke, Cumberland, Hutcheson, and Hume, argued that obligation is the practical force that empirical discoveries acquire in the process of deliberation.

On the other, a group including Cudworth, Shaftesbury, Butler, and, in some moments, Locke, viewed obligation as inconceivable without an autonomous will and sought (well before Kant) to develop a theory of the will as self-determining and to devise an account of obligation linked to that.