Saadiah Gaon and Petrus Alfonsi

Identifying sources is particularly difficult when authors had access to works or took part in oral exchanges in different languages and sociocultural milieus. This paper illustrates relevant methodological problems and possible solutions by discussing Petrus Alfonsi's possible use of Saadiah Gaon's Emunot ve-De'ot (Book of Beliefs and Opinions) as a source for his Dialogus. The presence of some parallels between both works has already been observed in two instances (the passages on the forms of knowledge and on the Trinity), but an attentive reading demonstrates still more similarities relating to these two subjects as well as in other parts of the Dialogus dealing with resurrection and allegorical exegesis. The use of Emunot ve-De'ot as a source is blurred by its adaptation to new argumentative needs and by the combination with other sources. There is evidence, however, both of a historical (Petrus Alfonsi's biography and knowledge of Arabic and Hebrew, circulation of Emunot ve- De'ot in Andalus) and a textual character (agreement in several details or in significant variants, clustering of parallels, similar contextualization of themes), that these parallels are not mere coincidences.