Joseph bar Ḥiyya became gaon of the Pumbedita yeshiva in Iraq in 825 and before this was av bet din (chief justice) under Abraham ben Sherira (816–828). He was nominated for the gaonate when Sherira was deposed in connection with the exilarchic succession dispute between David ben Judah and Daniel ben Saul.  He and Abraham ben Sherira apparently took opposite sides in the dispute, but it is uncertain which claimant each supported. They eventually agreed to share the leadership of the academy as co-geonim, but with Abraham enjoying superior status on public occasions. In his Epistle, Rav She…