The Castilian Jew Abner of Burgos/ Alfonso of Valladolid converted to Christianity around 1320, some seventy years before the mass persecutions of Jews that swept across the Iberian Peninsula in 1391. Although there is no direct or causal connection between Abner/Alfonso’s ideas and the events of 1391, many modern scholars have linked the two phenomena. This article examines Abner/Alfonso’s writings to determine if he expressed support for forced or mass conversion that might make such a connection logical. It shows that Abner/Alfonso’s statements on the subject of forced conversion are contradictory and express contrasting views in social, pastoral, philosophical, and theological terms. While he does seem to support social policies that pressure Jews to convert, he also speaks at length about the need to convince individual Jews with logical arguments and fair treatment. Although he does espouse a philosophical doctrine of determinism, he does not use this to argue in favor of forced conversion nor does he claim that such determinism frees the individual from judgment for good and bad choices. He ultimately argues that forced conversion would be contrary to God’s salvific plan for the Jews, which involves keeping them in subjugation and “captivity” as a just punishment for their rejection of Jesus. Although his arguments certainly played a part in the decline in Jewish-Christian relations in fourteenth-century Castile, scholars must proceed with caution in trying to establish a causal link between those arguments and the persecutions of 1391 and beyond.