Locke concerned himself with a philosophic inquiry into the nature of the mind itself, and was looked upon as a destroyer of the faith. Descartes based his philosophy on the rejection of authority in favor of human reason for which his works were honored by being placed on the Index in 1663. Hume, with the publication of the highly heretical "Treatise on Human Nature," threw consternation into the ranks of the theists. His theory of knowledge played havoc with the old arguments for belief in God and immortality of the soul. His works were widely read and were instrumental in leading to the philosophical agnosticism of the nineteenth century. Spinoza's religious views seemed in his time little short of atheism and brought him the hostility of both Jews and Christians, to which was added the excommunication from the synagogue. In his philosophy God and nature are equivalent terms and it is pantheistic only in the sense that if man is to have a god at all, nature must be that god, and whatever man considers godlike must be found in nature. Spinoza recognizes no supernatural realm and denies the survival of personal memory. Professor G. Boas, in his "Adventures of Human Thought," discusses the attitude of public opinion of the time of Spinoza. "He was the arch-atheist, the materialist, the subverter of all that was held most dear by the reigning powers. It was only after the French Revolution that he came into his own when certain Germans, captivated by Neo-Platonism, emphasized the pantheistic element in him. But by then Christianity had ceased to be a dominant intellectual force and had become what it is today, a folk belief." In the "Tractus Theologico-Politicus," Spinoza states: "When people declare, as all are ready to do, that the Bible is the Word of God teaching men true blessedness and the way of salvation, they evidently do not mean what they say, for the masses take no pains at all to live according to Scripture, and we see most people endeavoring to hawk about their own commentaries as the word of God, and giving their best efforts, under the guise of religion, to compelling others to think as they do. We generally see, I say, theologians anxious to learn how to wring their inventions and sayings out of the sacred text, and to fortify them with divine authority."