Descartes had shown that matter could be described entirely by extension and motion, with no purposes in it and no spirits behind it — and then, to save the soul and save God, he set thinking substance outside that machine and God outside them both. Everyone could see the seam, and a philosopher in Amsterdam pulled at it until the whole arrangement came apart: there is no outside. God and nature are one thing, and everything that happens follows from it as necessarily as the properties of a triangle follow from a triangle.
That sentence took a life to defend, and it cost him the community he was born into. In July 1656, before he had published a word, the Portuguese synagogue of Amsterdam read a ban over him from the Ark — expulsion, curses by day and by night, an instruction that no one speak with him or read anything he wrote. The document lists abominable heresies and monstrous deeds and specifies neither. The congregation had reason to be nervous: refugees from the Inquisition, tolerated by the Dutch on the understanding that they kept order among themselves, they could not afford a twenty-three-year-old asking in public whether the Torah had a divine author. He never sought readmission and never converted to anything. He took the Latin form of his name, Benedictus, and ground optical lenses for a living.
What he built afterwards is a moral argument dressed as geometry. The Ethics proceeds by definitions, axioms and numbered propositions, each with its proof, because Spinoza held that how to live can be deduced. The deductions are unforgiving: there is one substance, and mind and body are one thing described two ways. Free will is an illusion produced by knowing one's desires and not their causes. Nothing was made for anyone. What remains is understanding — grasping why things must be as they are, which loosens their grip. Blessedness, in his account, is not the wage paid for virtue but the virtue itself.
He published almost none of this while alive. The Theological-Political Treatise went out in 1670 without his name, under a false printer and a false city, and by 1674 the Court of Holland had banned it beside Hobbes's Leviathan. In 1673 the Elector Palatine offered him a chair at Heidelberg with an explicit guarantee of freedom to teach; he declined, having noticed the clause about not disturbing the established religion. In 1675 he carried the finished Ethics to Amsterdam to put it in press, learned that theologians were already telling the magistrates it proved there was no God, and carried it home again.
He died in The Hague in February 1677, at forty-four, of a lung disease. His friends printed the manuscripts that year over the initials B.d.S.; the States of Holland banned the book in June 1678 and Rome indexed it in 1679. For a hundred years Spinozist was an accusation. Then in 1785 Jacobi revealed that Lessing had confessed to knowing no other philosophy worth the name, and German thought turned overnight. Philosophers still divide over what his necessity leaves of praise, blame and choice; the readers it won include Goethe, Hegel, Herder, and eventually Einstein, who said that this was the God he believed in.