Born in Spain in 1488, Joseph Karo was taken by his family to nearby Portugal during the expulsion of 1492—before they fled again five years later to avoid forced conversation. Karo would go on to write magisterial commentaries on the seminal halakhic compendia of Moses Maimonides and Jacob ben Asher, before codifying his own scholarship in the Shulḥan Arukh—a Jewish legal handbook invested with an authority given to no work since the Babylonian Talmud. He was also one of the leading kabbalists of his day. Tamar Marvin describes his early life and intellectual formation:
Following . . . the route of so many Iberian exiles, [Karo’s] family found its way to the newly minted and bustling Ottoman empire, settling first at Constantinople (now Istanbul, or, as Jews called it, Custa). When Joseph’s father, Ephraim, died at a young age, his uncle took over his education. By 1522 Joseph sought his own fortune, moving to Adrianople (today’s Edirne), Nikopol, and then Salonika (something like, we might say, the Chicago, Miami, and Los Angeles of Turkey in those days).
Along the way, Karo met compatriots and brushed shoulders with the colorful messianic figure Solomon Molcho. Molcho, born Diogo Pires in Portugal, was a Marrano—the pejorative descriptor of forcibly converted Portuguese Jews. He returned to Judaism; was circumcised by another messianic pretender, David Reuveni; studied Kabbalah; and eventually made overtures to the pope and Holy Roman Emperor. The latter did not take kindly to Molcho’s messianic pretensions and had him tried, whereupon he was burned at the stake as a Christian heretic in 1532. This public martyrdom impressed itself upon Karo’s consciousness.
While still in Adrianople, at the age of thirty-four, Karo began work on his masterpiece, which would take him twenty years to complete. His goal was ambitious and born in worry: concern that the exigencies of the time—especially the traumatic dislocation of Iberian Jewry—were leading to a multiplicity of halachic rulings. This sense of unruly diversity was certainly informed by a key feature of early modernity, which, due to expulsions from Western Europe, brought together disparate Jewish communities.