Although not a rabbi, as Spanish chroniclers claim, he was well versed in the Talmud and in rabbinical literature. In order to show his zeal for the new faith he tried to win over to Christianity his former co-believers, and to throw suspicion on them and on their religion. For that reason he was called "megaddef" ("the blasphemer"), from the initial letters of his name, Maestro Geronimo de Santa Fé.