Prior to the 1263 Disputation of Barcelona, he followed Nicholas Donin's lead in attempting to ban the Talmud, which he argued had "irrational" textual material. As for his participation in the Disputation, it was his attempt to convert Nahmanides and other fellow Jews to Christianity.
Before the 1263 Barcelona Disputation, he followed Nicholas Donin's lead in trying to ban the Talmud, claiming its text contained "irrational" material. During the Disputation itself, he sought to convert prominent Jewish figures like Nahmanides to Christianity.