 Hume and Kant operate with two somewhat different conceptions of morality itself, which helps explain some of the differences between their respective approaches to moral philosophy. The most important difference is that Kant sees law, duty, and obligation as the very heart of morality, while Hume does not. In this respect, Kant’s conception of morality resembles what Bernard Williams calls “the moral system”, which defines the domain of morality primarily in terms of an unconditionally binding and inescapable form of obligation (Williams 1985: 193–94). Kant believes that our moral concerns are dominated by the question of what duties are imposed on us by a law that commands with a uniquely moral necessity. Like most eighteenth-century philosophers, he also believes that our moral lives are preoccupied with the question of how to be virtuous over a lifetime, but he defines virtue in terms of the more fundamental concepts of law, obligation, and duty. By contrast, these concepts play a role in Hume’s understanding, but they are far less central. For Hume, the broader and somewhat looser notion of “personal merit” lies at the heart of morality (EPM 9.1.1). Our moral concerns are dominated by the question of which motives are virtuous, and we answer this question by looking to the responses of our fellow human beings, who—when viewing things properly—approve of those motives and character traits that are useful or immediately agreeable (EPM 9.1.13). These are the terms that characterize duty and obligation for Hume, rather than the other way around.