This paper attempts to make clear the following points: 1. The system of the philosophy of John Locke is based on his Christian faith, and his main problem was both to investigate the moral principles and to acquire the knowledge of the existence of God, as the ground of morality. This problem is seen all through his works, from his early Essays on the Law of Nature, written shortly after 1660, to Two Treatises of Civil Government, 1690, and An Essay concerning Human Understanding, 1690. Locke deals with the Christian faith directly in his later work, The Reasonableness of Christianity, as delivered in the Scripture, 1695. 2. As it has been since his ESSAYS, the principle of knowledge in his ESSAY, bk. I and II, is the light of nature. But ...