This chapter focuses on some of the major writings of John Locke, who made an unequaled contribution to the emergence of secularism in general and political secularism in particular. He is an inventive and resourceful theorist, and many of the principal elements of mature secularism are present in his work. Locke emphasizes the political and social advantages that ensue when the state tolerates all religions, despite his allowance for some interference. There are two principal expressions of the secular disposition in Locke's writings. It is the first expression, found in the great works, Two Treatises of Government and A Letter on Toleration, which has exercised enormous influence in promoting secularism in the West. Yet the second expression contains instructive lessons for the student of secularism. Secular investigation must begin with the postulate that mind developed out of matter, out of the constituent elements of the universe, but that mind is not just another manifestation of matter.