In 1391, in the wake of a wave of bloody pogroms that swept Spain, Profayt Duran, along with tens of thousands of other Jews, was baptized a Christian. Privately, however, he continued to write treatises on Hebrew grammar and the Jewish calendar and to polemicize vigorously against Christianity. Reviewing Maud Kozodoy’s The Secret Faith of Maestre Honoratus, the first full-length biography of Duran, Frederic Raphael writes:
Before his conversion, Duran had prospered professionally as sage, physician, astrologer, and mathematician. Though excluded from the universities, Jews could find favor at court. Diplomatic doctors moved freely in Christian Spain. . . . As well as being guardians of Jewish science, philosophy, and literary culture, successful medical men, once rich, often became moneylenders.
Duran’s case is particularly fascinating because he was impelled publicly to embrace a religion he continued to scorn in private essay-letters. Secretly, Duran confessed his agony over the dichotomy in which “inner orientation cannot correspond to outward practice.” . . . As a converso, Duran may have guarded his tongue, but he was covertly outspoken with his pen.
[As a Jewish rationalist], Duran accepted the . . . “stark [Maimonidean] dichotomy between reason and revelation.” The distinction left science free to be “grounded in an assumption of the fundamental validity of rational thought.” Jewish religious belief neither muzzled scientific discovery nor tortured logic. . . . Duran saw that science set standards against which Christian dogma, transubstantiation in particular, could be anatomized.