The account of the origin of Mutazalism given by Shahrastani is widely accepted as the standard one. According to his account, once Hasan Basri (d. 110/728), one of the earliest Sufis, was imparting instructions to his pupil in a mosque. Before the lessons were finished, someone turned up and asked, whether they should regard the grave sinner as a believer or an unbeliever. Hasan Basri was on the point of giving a reply to this query when a long-necked pupil, Wasil bin Ata (d. 131/748), burst into discussion with the assertion that the perpetrator of grave sins is neither a complete unbeliever nor a perfect; he is placed midway between unbelief and belief - an intermediate state, i.e., manzila bayn al-manzilatayn (a position between the two positions). Having spoken he strode to another pillar of the mosque followed by a number of those in the circle. Hasan Basri shot a swift glance at him and said that, "He has withdrawn (i'tazala anna) from us." From this remark originated the name, Mutazila or Mutazalite, i.e., the Withdrawers or Secessionists. Other versions have a similar story, but the man who withdraws is not Wasil bin Ata but Amr bin Ubaid (d. 144/761). About the same time as al- Khayyat Ibn Qutayba wrote of Amr that he held the doctrine of Qadar and made propaganda for it; and he and his followers withdrew (i'tazala) from Hasan Basri and were called the Mutazila. Ibn Munabbih says that the title of Mutazila came into vogue after the death of Hasan Basri. When Hasan passed away, Qatada succeeded him and continued his work. Amr bin Ubaid and his followers avoided the company of Qatada, therefore, they were given the title of al-Mutazila.
The material so far examined shows a divergence of view on whether the leader was Amr or Wasil. Yet other considerations, however, suggest that the originator of the sect in the form in which it became famous was neither of these men but Abul Hudhayl and his generation. The statement of Ibn Hazm shows that the Mutazalites were a group of rationalists who judged all Islamic beliefs by theoretical reason and renounced those that related to all that lay beyond the reach of reason. They raised the problems of freewil and determinism, the attributes of God, the nature of the soul, the createdness of the Koran, etc. In sum, an endless chain of polemics was started by them in the Muslim society to such extent that Islam began to be assailed both from inside and outside. The situation was fraught with great danger for the faith. When the various forces arrayed themselves against the extremism of the rationalists, the orthodox ulema also reacted against them negatively.