The "Reasonableness of Christianity" is Locke’s major book of theology. Before publishing this book in 1695, Locke always preferred to keep his religious ideas for himself. It was both his interest in some of the theological controversies of the day – particularly in the antinomian and deist controversies – and his effort to establish morality on convincing grounds that led him to turn to biblical theology. A markedly religious conception of life, however, conditioned his moral inquiry since the composition of the manuscript "Essays on the Law of Nature" (1664) and informed his reflections on morality in the "Second Treatise of Civil Government" and "An Essay concerning Human Understanding" (1690). In these works, Locke emphasized the necessity to believe in, and obey, a divine creator and legislator, and he described the moral law as God-given and, consequently, discoverable by natural reason (at least in principle) or through divine revelation. Nevertheless, Locke’s struggle to ground morality in theoretical foundations proved fruitless and eventually led him to turn, in the "Reasonableness," to a Scripture-based theological ethics in order to promote moral practice.