Al-Qadi al-Nu'man

Abū Ḥanīfa al-Nuʿmān ibn Muḥammad ibn Manṣūr ibn Aḥmad ibn Ḥayyūn al-Tamīmiyy or as ibn Ḥayyūn was an Isma'ili jurist and the official historian of the Fatimid Caliphate. He was also called Qāḍī al-Quḍāt "Jurist of the Jurists" and Dāʻī al-Duʻāt "Missionary of Missionaries".

Biography

Born in Kairouan, in what is now Tunisia, al-Nu'man converted to Isma'ilism and began his career in Ifriqiya under the first Fatimid caliph, Abdullah al-Mahdi Billah, quickly rising to become the most prominent judge of the Fatimid state.
His father, Muhammad ibn Mansur, had trained as a Sunni Maliki jurist in Qayrawan. Some have suggested that al-Qadi al-Numan's father converted to Isma'ili Shi'ism prior to the founding of the Fatimid Caliphate, suggesting that al-Qadi al-Nu'man was raised an Isma'ili. Ibn Taghribirdi has alternatively suggested however that al-Qadi al-Nu'man was a Hanafi prior to his own conversion to Isma'ili Shi'ism. This has largely been dismissed due to the assumption that Ibn Taghribirdi based this on the apparently erroneous idea that the Hanafi school had been pre-dominant in North Africa until al-Mu'izz ibn Badis imposed the Maliki school. However, Ibn Taghribirdi's assertion may have alternatively been based on the fact that al-Qadi al-Numan's patronymic, "Abu Hanifah," matches with the name of the eponymous founder of the Hanafi school. This may lend support to the idea that his father, Muhammad, may have converted to the Hanafi school prior to any conversion to Isma'ili Shi'ism. Regardless, al-Qadi al-Numani certainly was an Isma'ili when he entered the employ of the Fatimids at a young age.
During his lifetime, al-Qadi al-Nu'man served four Fatimid Caliphs:

During al-Nu'man's fifty years of service to the Fatimids, he wrote a vast number of books under the encouragement of the caliphs on history, biography, fiqh and the esoteric interpretation of the Quran. After the Fatimid conquest of Egypt and Syria, al-Nu'man left Ifriqiya and travelled to the newly founded city of Cairo, where he eventually died in 974 CE/363 AH.
Under al-Mahdi began the career of Qadi al-Numan, the founder of Ismaili law and author of its most authoritative compendium, the Kitab da'a'im al-Islam. In the absence of an Ismaili legal tradition, Qadi al-Numan relied primarily on the legal teaching of Imams Muhammad al-Baqir and Ja'far al-Sadiq, transmitted by Twelver Shii traditionists, and secondarily on Zaydi traditions.
It gives the imam authority for determining the beginning of the month without regard to the sighting of the new moon as required by all other Muslim legal schools. Since the early Fatimid period the beginning of the months was generally established in practice on the basis of astronomical calculation and thus often fell one or two days earlier than for other Muslims; this discrepancy often caused intercommunal quarrels about the beginning and end of the fasting month of Ramadan.

His works

Al-Nu'man's work consists of over 40 treatises on fiqh, history, religious beliefs and Quranic esoteric exegesis. Fuat Sezgin cites 22 works by him.
Al-Nu'man's most prominent work, the Da'a'im al-Islam, which took nearly thirty years to complete, is an exposition of Isma'ili jurisprudence. This work was finally completed during the reign of the fourth caliph, al-Mu'izz li-Din Allah, was accepted in its time as the official code of the Fatimid Caliphate, and serves to this day as the primary source of religious law for some Musta'li communities, particularly Tayyibi Isma'ilis. Iran incorporated the Da'a'im al-Islam into their constitution. The book consists of 32 chapters in two volumes. The first volume consists of 7 chapters discussing the Seven pillars of Ismailism. The second volume consists of 25 chapters about various topics relating to different facets of life.
Alongside his Pillars of Islam, the Foundation of Symbolic Interpretation, is one of al-Nu’man's most celebrated works and deals with esoteric interpretation. In the author's own words, “Our aim is to explain the inner dimension of what we laid out in the book Daʿāʾim al-Islām, so that this book may be a source for the inner meaning, just as that one is for the external form.
Qadi al-Nu'man believed that it is important to recognize and understand the symbolism behind the stories in the Quran based on certain verses that point to an inner meaning such as: “Thus your Lord will choose you and teach you the symbolic interpretation of events ”. In his work Foundation of Symbolic Interpretation, he indicates that God made the Quran the miracle of Muhammad and its inner meaning the miracle of the Imams. Just as nobody can replicate the miracle of the Book, nobody can produce its inner meanings except for the Imams. This sacred knowledge is passed down through generations in their lineage and is entrusted to them.
Another major work, the Kitab iftitah al-da‘wa wa-ibtida’ al-dawla narrates the rise of the Fatimids. It mentions the initial stages of the Isma'ili dawah in Yemen under Ibn Hawshab. It also discusses Abu Abdallah al-Shi'i's correspondence with the Kutama Imazighen and their military expeditions, leading to the conquest of the Aghlabids, who ruled Ifriqiya. It discusses Imam al-Mahdi's emigration from Salamiyah, his captivity in Sijilmasa and eventual release, culminating in the establishment of the Fatimid state in 909. The book also gives an account of the circumstances leading to the revolt of al-Shi'i, for which it holds responsible the incitement of his elder brother Abu al-Abbas, and his later execution. It also gives a description of the Fatimid state up to the year 957, when the book was completed.
Ikhtilaf usul al-madhahib was a refutation of Sunni principles of Islamic jurisprudence written at roughly the same time as the earliest of such works. Nu'man's book borrows heavily from those of Dawud al-Zahiri, Muhammad bin Dawud al-Zahiri and al-Tabari, three Sunni authors about whom Nu'man displays complex mixed feelings. It has been noted that while Nu'man's book is famous, it was not the first Ismali refutation of Sunni juristic principles.
Al-Nu'man's other major works are the Kitab al-majalis wa’l-musayarat and the Kitab al-himma fi adab atba‘ al-a’imma.