"He was born in Ahwaz in Iran. He belonged to the Makhzumi clan and was the mawla (freed slave) of Imam Muhammad al-Bakir and Imam Jafar Sadik. His surname al-Qaddah is usually taken to mean oculist, which seems extremely doubtful. It is a word connected with al-qidah i.e., an ancient Arab play or a form of divination with the help of arrows. Tusi (d. 460/1068) in Tahdhibul Ahkam while dealing with Maymun al-Qaddah, explains the word as "a man who practises the game of qidah (yabra'ul qidah). Thus, he was a specialist in divination with the help of arrows.

Maymun al-Qaddah was a very pious man of ascetic life. Because of his close association and faithfulness, he was chosen for the task of stimulating the secret Ismaili mission, and became the primary architect in articulation of the Ismaili mission.

It also appears that the activities of Maymun al-Qaddah had been exaggerated by the Arabs because of being an Iranian. The derogations of his Arab enemies can be judged from their baseless propaganda that he and his son, Abdullah bin Maymun were against the Islamic tenets, and had planned to blow it up, and broadcast that the Ismailism was typically an Iranian. Silvestre de Sacy (1758-1838) therefore, is inclined to make his judgment curiously in his Expose de la Religion des Druzes (Paris, 1838, p. 31) that the Ismaili doctrine is typically Iranian, and later E.G. Browne in A Literary History of Persia (New York, 1902, 1:405) also advanced same views. Being influenced with the Arab propaganda, the orientalists adopted the theory that the Ismailis were of Iranian origin, which has been however falsified by W. Montgomery Watt, vide Islamic Philosophy and Theology (Edinburgh, 1985, p. 126). This idea led the other scholars to theorize the Ismailism not merely an anti-Arab movement, but more so an anti-Islamic revolution; but the recent researches have ruled out such groundless propaganda.

Allegorical interpretation (tawil) of the Koran was in vogue among the people of all walks of life, attempting the evolution of a religious philosophy. The Ismaili da'is had purified the Islamic Shariah polluted by the ignorants. The draining off the adulterated tenets through the agency of tawil by Maymun al-Qaddah and his son was violently opposed and misinterpreted by the Arabs, who were basically against the philosophical approaches. Most of the historians tried to project Maymun al-Qaddah as an enemy of Islam, planning to destroy it from within by founding the Ismaili movement and evolving its doctrines in such a way as to present Zoroastrian or Manhchean teachings in the Islamic garb. These historians want us to believe that Maymun al-Qaddah had nothing but contempt for Islam and fierce hatred towards the Arabs and that they conceived the idea of a secret society which should be all things to all men, and which, by playing on the strongest passions and tempting the inmost weaknesses of human nature, should unite malcontents of every description in a conspiracy to overthrow the then existing Abbasid regime. These are fantastic allegations levelled with a calculated purpose to discredit the Ismailis in the eyes of orthodox Muslims. Many eminent orientalists like de Goeje, R.A. Nicholson, etc., have erred in taking this story from the prejudiced historians.

Evincing their utter ignorance, the philosophy was officially banned in the orthodox orbits, propagating that it was the tool used by the Ismaili da'is to undermine Islam. Syed Abid Ali Abid writes in Political Theory of the Shi'ites (cf. A History of Muslim Philosophy, Germany, 1963, 1:740) that, "The orientalists - nay even such an erudite Iranian scholar as Muhammad Qazwini, the editor of Tarikh-i Jhangusha by Ata Malik Juvaini - were misled by the voluminous Abbasid propaganda, hostile commentary of the orthodox Shiites, and the specious argument of those opposed to the Ismailites, into thinking that Maimun and his son Abd Allah were opposed to the tenets of Islam or were inspired by the hatred for the Arabs." J.J. Saunders also advanced his doubts in this context, vide A History of Medieval Islam (London, 1965, p. 128). Besides, Maymun al-Qaddah is shown as a real founder of Ismailism, which is starkly a fabrication, and it was apparently a "brain-wave" on the part of Ibn al-Razzam, whose historical character is yet doubtful.

Maymun al-Qaddah was canonized in the rank of hijab (screen), whose function was in addition to screen the real Imam from his enemies, and was thus the hijab of Imam Ismail and his son. According to W. Ivanow in The Rise of the Fatimids (Calcutta, 1942, p. 56), "The idea of the hijab, or a dignitary, whose duty was to pretend to be the Imam, thus sheltering the real holder of the office."

The functions of the hijab in pre-Fatimid period were the same as the hujjat. The hijab was the most trusted, tested, devoted and reliable dignitary who was ostensibly assigned with high religious authority, posing as an Imam to the ordinary people, accepting oath of allegiance on behalf of the concealed Imam. According to Kashfu'l-Asrar by Jawbari, quoted by L. Massignon, Maymun al-Qaddah died in 210/825, leaving behind two sons, Aban and Abdullah.