Abraham Miguel Cardozo is one of the most unusual and complex figures in the history of Jewish thought, but his identification with the Sabbateans caused him to be largely excluded from the study of that history, in his time and in ours. He had no impact to speak of on the larger development of Jewish ideas; yet, his biography and thought shed much light on the peculiarities of late-seventeenth-century Jewish identity. Cardozo was born to a New Christian (converso) family in Spain in 1626, and, after fleeing the Iberian Peninsula with his older brother, Isaac (who was the subject of a well-known biography by Yosef Hayim Yerushalmi), reverted to Judaism in Italy in 1648. He had already completed university studies by this time, and his fine Iberian training in philosophy and theology left its mark on all his writings.