On 27 July 1656, in the Portuguese synagogue of Amsterdam, the parnassim pronounced herem on a twenty-three-year-old merchant's son named Baruch Spinoza. The text survives, and it is the harshest the community ever issued: cursed by day and cursed by night, cursed in his going out and his coming in; none may speak with him, do business with him, read anything he writes, or come within four cubits of him. The stated grounds are abominable heresies and monstrous deeds, unspecified; Spinoza had published nothing. Whatever the young man was saying, likely the positions that later filled the Ethics and the Theological-Political Treatise, denial of providence, of the soul's immortality as commonly understood, of the divine origin of the Torah's text, the community of former conversos, itself insecure in Calvinist Amsterdam, judged it intolerable.
Spinoza neither recanted nor converted. He accepted the ban, changed Baruch to Benedictus, ground lenses, and wrote; he is the rare excommunicate of any tradition who simply continued, building outside every communion one of the great philosophical systems of Europe. The ban was never lifted, and the question of lifting it has become a small modern institution of its own: petitions to Amsterdam's rabbinate have been considered and declined, most recently after a 2015 symposium, on the reasoning that the community that imposed it no longer exists to speak for. The herem on Spinoza thus outlived its makers, a monument to the boundary it drew and to the thinker who walked past it.