Now that I have sketched my main purpose, it is time to ex­plain why a book dedicated to new ideas on the nature and signif­icance of human feeling s… - Benedictus de Spinoza

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."

He [Spinoza] does not prove the existence of God, existence is God. And if for this reason others would brand him Atheum then I would praise him and call him theissimum and christianissimum. [Original in German: Du erkennst die höchste Realität an, welche der Grund des ganzen Spinozismus ist, worauf alles übrige ruht, woraus alles übrigefliest. Er [Spinoza] beweist nicht das Daseyn Gottes, das Daseyn ist Gott. Und wenn ihn andre deshalb Atheum schelten, so mögte ich ihn theissimum ja christianissimum nennen und preisen.]

This work [The Savage Anomaly] was written in prison. And it was also conceived, for the most part, in prison. Certainly, I have always known Spinoza well. Since I was in school, I have loved the Ethics (and here I would like to fondly remember my teacher of those years). I continued to work on it, never losing touch, but a full study required too much time. Once in prison I started from the beginning: reading and making notes, tormenting my colleagues to send me books. I thank them all with all my heart.