Leo Strauss, "Locke's Doctrine of Natural Law" in What is Political Philosophy? And Other Studies (Chicago: University of Chicago Press, 1959), 197-220.
Locke’s notion of natural right appears to be much closer to the traditional view as restated by Hooker than to the revolutionary view of Hobbes. Closer inspection would show that this appearance is deceptive and must be traced to Locke’s peculiar caution. To indicate with utmost brevity the main point, Locke says on one hand that, in order to be a law, the law of nature must not only have been given by God, it must in addition have as its sanction divine “rewards and punishment, of infinite weight and duration, in another life.” On the other hand, however, he says that reason cannot demonstrate that there is another life. Only through revelation do we know of the sanctions of the law of nature, or of “the only true touchstone of moral rectitude.” Natural reason is therefore unable to know the law of nature as a law. Yet Locke contends that there is “a law knowable by the light of nature, that is, without the help of positive revelation. If there is to be such a law this law must therefore consist of a set of rules whose validity does not suppose life after death or a belief in life after death.