al-Muḥāsibī was the founder of the Baghdad School of Islamic philosophy, and a teacher of the Sufi mastersJunayd al-Baghdadi and Sirri Saqti. His full name is Abu Abdullah Harith bin Asad al-Basri. He was born in Basra in 781. Muhasibi means self-inspection/audit. It was his characteristic property. He was a founder of Sufi doctrine, and influenced many subsequent theologians, such as al-Ghazali. The author of approximately 200 works, he wrote about theology and Tasawwuf, among them Kitab al-Khalwa and Kitab al-Ri`aya li-huquq Allah.
Life
His parents left Basra for Baghdad shortly after his birth, perhaps inclined to the economic opportunities in the new capital. His father became wealthy, though al-Muhasibi refused it. Despite the affluentlifestyle available to him, he retained am ascetic quality from Al-Hasan al-Basri. The Sufis of his time has taken on certain practices, such as wearing woolen clothing, reciting the Qur'an at night, and limiting the kind and quantity of food eaten. He saw that Sufi practices can help control the passions, but can also result in other problems like hypocrisy and pride. When outward piety becomes a part of one's image, it can mask hidden problems with the ego. Both the inner and outward states must be rectified. Constant self-examination in anticipation of the Day of Judgement was his proposed method for developing awareness of the inner self and purifying the heart. Al-Muhasibi later joined a group of scholars of theology, led by Abdullah ibn Kullāb. They criticized the Jahmis, Mu'tazilis, and Anthropomorphists. The Mu'tazilis argued that the Qur'an was created, while Ibn Kullab argued against the createdness of the Qur'an by introducing a distinction between the speech of God and its realization: God is eternally speaking, but he can only be mukallim, addressing Himself to somebody, if this addressee exists. In 848, the caliph al-Mutawakkil ended the Mihna, and, two years later, banned the Mu'tazilites' theology. In al-Khalwa, in a discourse on fear and hope: Al-Khalwa's argument elsewhere cites al-Hasan al-Basri. The above pericope was later transplanted into a fictional response by al-Hasan to 'Umar b. 'Abd al-Aziz.