"Some important intellectual figures of the day made their way to the modest rooms he rented in the Hague in his last years, including the up-and-coming young go-getter Gottfried Wilhelm Leibniz, who would emerge as one of the most dazzling figures in the seventeenth century's impressive lineup of genius. Leibniz spent a few days with Spinoza, conversing on metaphysics. The only written record of their extensive conversations was a slip of paper on which Leibniz had written down, for Spinoza's approval, a proof for God's existence. Leibniz was profoundly influenced by Spinoza's ideas but sought always to conceal his philosophical debt, and is on record as denouncing the philosopher. When a professor of rhetoric at the University of Utrecht, one Johan Georg Graevius, wrote to Leibniz, castigating the Tractatus Theologico-Politicus as a "most pestilential book," whose author "is said to be a Jew named Spinoza, but who was cast out of the synagogue because of his monstrous opinions," Leibniz prudently chimed in with his own diplomatic calumny: "I have read the book by Spinoza. I am saddened by the fact that such a learned man has, as it seems, sunk so low.""