The Cairo Geniza is the largest and rich­est store of doc­u­men­tary evi­dence for the medieval Islam­ic world. This book seeks to rev­o­lu­tion­ize the way schol­ars use that trea­sure trove. Phillip I. Ack­er­man-Lieber­man draws on legal doc­u­ments from the Geniza to recon­ceive of life in the medieval Islam­ic mar­ket­place. In place of the shared prac­tices broad­ly under­stood by schol­ars to have tran­scend­ed con­fes­sion­al bound­aries, he reveals how Jew­ish mer­chants in Egypt employed dis­tinc­tive trad­ing prac­tices. High­ly influ­enced by Jew­ish law, these com­mer­cial prac­tices served to man­i­fest their Jew­ish iden­ti­ty in the medieval Islam­ic con­text. In light of this dis­tinc­tive­ness, Ack­er­man-Lieber­man pro­pos­es an alter­na­tive mod­el for using the Geniza doc­u­ments as a tool for under­stand­ing dai­ly life in the medieval Islam­ic world as a whole.