Isaac Orobio de Castro was born Baltazar Orobio de Castro in Braganza, Portugal. He grew up among crypto-Jews who were trying to preserve some of their heritage in the face of the Spanish Inquisition. He became an important Spanish doctor and a professor of metaphysics. He was arrested by the Inquisition for secretly practicing Judaism. After being tortured and tried, he was released. He then fled Spain for France, where he became professor of pharmacy at Toulouse (c. 1660). Finally, deciding to abandon living as a Christian, he moved to Holland, where in 1662 he changed his name from Baltazar to Isaac and became one of the leading intellectual figures and a medical practitioner in the Spanish-Portuguese Jewish community in Amsterdam. When he arrived in the Jewish community, he learned that there had been trouble about a former classmate of...