Baruch Spinoza (1632–77) was born in Amsterdam of Jewish parents who were refugees from the Spanish Inquisition. They had fled Spain in quest of the religious tolerance of the Netherlands. Spinoza was brought up an orthodox Jew and studied the work of many Jewish philosophers, including Moses Maimonides. Spinoza was well versed in Jewish Arabic philosophy and theology, but he became increasingly influenced by modern rationalism and science, particularly the writings of Hobbes and Descartes.

His thinking moved further and further away from traditional Jewish thought, until in 1656 he was excommunicated from his synagogue for alleged heresies. He was a teacher, but earned his living primarily by being a lens grinder and polisher. He was a man of personal integrity who led a frugal lifestyle. He turned down a professorship at the University of Heidelberg and a pension from the French king, in both cases because he wanted to avoid any risk of losing his intellectual independence. Evidence suggests that he lived a life of simplicity, courage, and personal charm.

He kept company with a group of Protestants known as the “Collegians,” a sect without priests. In 1661 he began writing a Treatise on the Correction of the Understanding, a work that shows the influence of and also criticizes Descartes. In 1663 he also began to write his major philosophical work, the Ethics, but it was not completed until 1675 because he had put it aside in order to write a treatise in defense of liberty, thought, and speech.

The Ethics had to wait for publication until after his death, but it was his greatest work. It is presented in the form of Euclid's Elements, with numbered definitions, axioms, and propositions, each with a demonstration. Like Descartes, Spinoza had imposed a geometric, thoroughly deductive method in his style of philosophy. He died at the age of forty-five, the victim of a pulmonary condition, probably the result of his years as a lens grinder.