  The next two centuries in European philosophy can be described in terms of two lines of development, rationalism and empiricism, both of which led, in different ways, to the possibility of a greater detachment of ethics from theology. The history of rationalism from René Descartes (1596–1650) to Gottfried Wilhelm Leibniz (1646–1716) is a history of re-establishing human knowledge on the foundation of rational principles that could not be doubted, after modern science started to shake the traditional foundations supported by the authority of Greek philosophy and the church. Descartes was not primarily an ethicist, but he located the source of moral law (surprisingly for a rationalist) in God's will. The most important rationalist in ethics was Benedict de Spinoza (1623–77). He was a Jew, but was condemned by his contemporary faith community as unorthodox. Like Descartes, he attempted to duplicate the methods of geometry in philosophy. Substance, according to Spinoza, exists in itself and is conceived through itself (Ethics, I, def. 3); it is consequently one, infinite, and identical with God (Ethics, I, prop. 15). There is no such thing as natural law, since all events in nature (‘God or Nature’) are equally natural. Everything in the universe is necessary, and there is no free will, except in as far as Spinoza is in favor of calling someone free who is led by reason ( Ethics, I, prop. 32). Each human mind is a limited aspect of the divine intellect. On this view (which has its antecedent in Stoicism) the human task is to move towards the greatest possible rational control of human life. Leibniz was, like Descartes, not primarily an ethicist. He said, however, that ‘the highest perfection of any thinking being lies in careful and constant pursuit of true happiness’ (New Essays on Human Understanding, XXI, 51). The rationalists were not denying the centrality of God in human moral life, but their emphasis was on the access we have through the light of reason rather than through sacred text or ecclesiastical authority.