ALCASTIEL, JOSEPH , Spanish kabbalist, who lived in Játiva, Aragon, at the time of the expulsion of the Jews in 1492. While there is no evidence that Alcastiel was among the exiles he is indeed mentioned by R. Isaac ha-Kohen of Játiva, an expellee from Valencia. A recently published treatise contains Alcastiel's responsa to 18 questions purportedly asked by Judah *Ḥayyat, although it is not known that Alcastiel ever lived in Italy or knew Ḥayyat: Ḥayyat does not mention him in his writings nor do his writings show the influence of Alcastiel's work. On the other hand, Alcastiel's ideas, distinguished by their originality and insight, influenced other important kabbalists in the generation after the expulsion from Spain, such as Meir ibn *Gabbai, Solomon ha-Levi *Alkabeẓ, Moses *Cordovero, and, almost certainly, Isaac *Luria. According to one account, these responsa were written at Játiva in 1482. The treatise entitled Ma'amar Mufla al ha-Tanninim ("Wondrous Treatise on the Sea Monsters"; Ambrosian Library, Milan, Ms. 62/12) is ascribed to Ha-Ḥakham ha-Elohi Alcastilo ("the divine scholar Alcastilo"). Judging by its content and style, the author of this was Joseph Alcastiel and not Joseph b. Samuel of Catalonia as suggested in the catalog.
Scholem, in: Tarbiz, 24 (1954/55), 167–206. add. bibliography: M. Idel, "Chronicle of an Exile: R. Isaac ben Hayim Ha-Kohen of Jativa," in: Y. Assis and Y. Kaplan (eds.), Jews and Conversos at the Time of the Expulsion (1999), 259–71 (Heb.).