Cudworth's view of moral obligation may seem to contrast with none more sharply than with Locke's. Certainly this is the impression one gets from Essays on the Law of Nature. Here morality obligates because its demands emanate from a source that is external and superior to the moral agent; moral obligation is rooted in a juridical relation of superior authority obtaining between God and His creatures. Even so, Locke also implies that what can rationally motivate serves as a constraint on divine command – since God cannot sensibly issue commands that agents will lack rational motives to obey – and thus on moral obligation. And even in the Essays he holds that the structure of rational human motives is what makes it necessary for God to institute a system of morality in the first place. It is precisely because human agents would lack adequate motive to act in mutually advantageous ways without supernaturally sanctioned directives that God must establish these. This brings into the picture a connection between obligation and a source of rational motivation. Motivation is no part of Locke's understanding of what moral obligation is in the Essays, but it is nonetheless central to his account of why there should be such a thing.

By the time of the Essay, Locke is even clearer that obligation must connect closely to motive. Leaving out logic and semantics, all knowledge can be divided into theoretical and practical, he now says.