Amr Ibn Ubayd ibn Bāb (, died 761) was one of the earliest leaders in the "rationalist" theological movement of the Mu'tazilis, literally 'those who withdraw themselves' – which was founded by Wasil ibn Ata (died 749). Of Iranian descent, he was a student of the famous early theologian Hasan al-Basri, and led the Mutazilis during the early years of the Abbasid caliphate. He generally followed a quietist political stance toward the Abbasid political establishment. Life His grandfather had been captured when the Muslims conquered Kabul under Abd Allah ibn Samora in 663 and again in 665. Amr's father had served as a sergeant under al-Hajjaj, but by profession he was a weaver; Amr had learned the same craft and thus may have made an early acquaintance with Wasil ibn Ata. Their close personal relations are attested by the fact that Wasil married his sister. Doctrinally, they had disagreements in the beginning; Wasil is said to have converted Amr to his Mu'tazilite opinion in a long discussion. More than Wasil, Amr had belonged to the circle of close disciples around Hasan al-Basri, whose Tafsir he transmitted. Mu'tazila According to the Muslim heresiographers, members of the movement adhered to five principles, which were clearly enunciated for the first time by Abu al-Hudhayl. These were: (1) the unity of God; (2) divine justice; (3) the promise and the threat; (4) the intermediate position; and (5) the commanding of good and forbidding of evil (al-amr bil ma'ruf wa al-nahy 'an al munkar). It is said that when Hasan al-Basri was questioned about the position of the Muslim who committed a grave sin, his pupil Wasil bin 'Ata' said that such a person was neither a believer nor an unbeliever, but occupied an intermediate position. Hasan was displeased and remarked, 'He has withdrawn from us (i'tazila 'anna)', at which Wasil withdrew from his circle and began to propagate his own teaching. The historicity of this story has been questioned on the ground that there are several variants: according to one version the person who withdrew was Amr ibn Ubayd, and according to another the decisive break came in the time of Hasan's successor Qatada ibn De'ama. Moreover, it is noteworthy that at least one influential member of the Basra school, Abu Bakr al-Asamm, rejected the notion of an intermediate position and argued that the grave sinner remained a believer because of his testimony of