Abū Manṣūr ʿAbd al-Qāhir ibn Ṭāhir bin Muḥammad bin ʿAbd Allāh al-Tamīmī al-Shāfiʿī al-Baghdādī (Arabic: أبو منصور عبدالقاهر ابن طاهر بن محمد بن عبدالله التميمي الشافعي البغدادي), more commonly known as Abd al-Qāhir al-Baghdādī (عبد القاهر البغدادي) or simply Abū Manṣūr al-Baghdādī (أَبُو مَنْصُورالبغدادي) was an Arab[4] Sunni scholar from Baghdad.
[4] Ibn 'Asakir writes that Abu Mansur met the students of the companions of Imam al-Ashari and acquired knowledge from them.
Abu Mansur was known as a wealthy man where he donated his whole fortune to the scholars of wisdom until he was qualified to instruct in seventeen various subjects, including fiqh, usul, arithmetic, law of inheritance and theology.
[5] Due to Turkmen riots near the end of his life, Abu Mansur was forced to flee from Nishapur and established himself as a venerable citizen of Isfayayin, where he died in 449/1038.
[10] Abu Uthman al-Sabuni highly praised him and said: “one of the imams of the principles of the Religion and foremost authorities of Islam by consensus of its most eminent and competent scholars.”[5] 'Abd al-Qahir al-Baghdadi was a prolific writer who wrote on numerous subjects and authored several quality books including Kitāb Uṣūl al-Dīn, a systematic treatise, beginning with the nature of knowledge, creation, how the Creator is known, His attributes, etc.... and Al-Farq bayn al-Firaq which takes each sect separately, judges all from the standpoint of orthodoxy and condemns all which deviate from the straight path.