Spinoza’s personal life was, as he wished it to be, simple and relatively isolated. There was a small circle of devoted friends, freethinking Christians from various dissenting Protestant circles, who regarded Spinoza as their master and closely studied, and guarded, his thoughts. He combined a Marranoist cautious discretion about revealing his true views to the dangerously narrow-minded with a touching faith in the power of reason to persuade. So he published his Tractatus Theologico-Politicus (The Treatise on Theology and Politics) anonymously, but also hoped that it would convince the powers that be of its main conclusion, which is succinctly stated in the book’s subtitle: Wherein is set forth that freedom of thought and speech not only may, without prejudice to piety and the public peace, be granted; but also may not, without danger to piety and the public peace, be withheld. The book evolves into one of the most impassioned defenses of a free democratic state in the history of political theory, an eloquent plea for the separation of church and state. Spinoza allowed himself to hope that, should its argument for tolerance find its mark, he might be able to publish the work on which he had been toiling for years. The rain of abuse that poured down on the author of the Tractatus, whose true identity was soon an open secret throughout Europe, made him a very dangerous man to even remotely acknowledge, and all but foreclosed the possibility of his publishing his magnum opus in his lifetime. This is The Ethics, a work that makes all the claims for reason that have ever been made.

Some favors came his way. The University of Heidelberg, which had fallen from its perch of previous glory through the prolonged tribulations of the Thirty Years’ War, had no professor of philosophy on staff and, in the name of Karl Ludwig, Elector Palatine, offered him a chair of philosophy.