In the _Essay on the Human Understanding_, Bk. IV., ch. x., Locke attempts to prove the existence of a God, which, though God has given us no innate idea of Himself, he regards as "the most obvious truth that reason discerns," and as resting on evidence equal to mathematical certainty. Morality is, he maintains, entirely based upon the Will of God. If there were no God, there would, for him, be no morality, and this is the reason of his denying to Atheists the protection of the State. In the chapter on the Existence of God he says expressly that this truth is so fundamental that "all genuine morality depends thereon," and almost at the beginning of the _Essay_ (Bk. I., ch. iii., § 6), while acknowledging that "several moral rules may receive from mankind a very general approbation, without either knowing or admitting the true ground of morality," he maintains that such true ground "can only be the Will and Law of a God, who sees men in the dark, has in his hand rewards and punishments, and power enough to call to account the proudest offender." Again, "the Rule prescribed by God is the true and only measure of Virtue." But how are we to ascertain this rule? "God has by an inseparable connexion joined Virtue and Public Happiness together," and hence we have only to ascertain, by the use of the natural reason, what on the whole conduces most to the public welfare, in order to know the Divine Will. The rules, when arrived at, have a "moral and eternal obligation," and are enforced by fear of "the Hell God has ordained for the punishment of those that transgress them." This form of Utilitarianism, resting on a theological basis and enforced by theological sanctions, is precisely that which afterwards became so popular and excited so much attention, when adopted in the well-known work of Paley. According to this system, we do what is right simply because God commands it, and because He will punish us if we disobey His orders. "By the fault is the rod, and with the transgression a fire ready to punish it." But, notwithstanding the divine origin and the divine sanction of morality, its measure and test are purely human. Each man is required by the Law of God to do all the good and prevent all the evil that he can, and, as good and evil are resolved into pleasure and pain, the ultimate test of virtue or moral conduct comes to be its conduciveness to promote the pleasures and avert the pains of mankind. Bentham, whose ethical system, it may be noticed, differed mainly from that of Locke and Paley by not being based on a theological foundation, extends the scope of morality to all sentient creatures, capable of pleasure and pain.