The Ismailis, among whom are the followers of the Aga Khan, rose to prominence during the fourth Islamic/tenth Christian century. They developed a remarkably successful intellectual programme to sustain and support their political activities, promoting demands of Islamic doctrine together with the then newly imported sciences from abroad. The high watermark of this intellectual movement is best illustrated in the writings of the Ismaili theoretician Abu Ya´qub al-Sijistani. Using both published and manuscript writings of al-Sijistani that have hitherto been largely hidden, forgotten or ignored, Dr Paul Walker reveals the scholar's major contribution to the development of philosophical Shiism. He analyses his role in the Ismaili mission (da'wa) of that time and critically assesses the major themes in his combination of philosophy and religious doctrine.

The seminal contribution, known as the Condorcet Jury Theorem, observes that under a specific set of conditions an increase in the size of a group tasked with making a decision leads to an improvement in the group's ability to make a good decision. An assumption under-appreciated is that the competency of the members of the group is assumed to be exogenous. In numerous applications, members of the group make investments to improve the accuracy of their decision making (e.g. pre-meeting efforts). We consider the collective action problem that arises. We show that if competence is endogenous, then increases in the size of the group encourages free riding. This trades off with the value of information aggregation. Thus, the value of increased group size is muted. Extensions illustrate that if committee members are allowed to exit/not participate, then the equilibrium committee size is reduced. Additionally, (non-decisive) supermajority voting rules encourage the investments and, consequently, individual competence.

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Dhimmī (non-Muslim subjects, mostly Christians and Jews, who were afforded protection by the Islamic state) persecution in Islamic Egypt included most notably that instigated by the Fatimid caliph al-Ḥākim from about 395/1004 until near the end of his reign in 411/1021. This ruler imposed burdensome restrictions and sumptuary regulations on Jews and Christians, causing significant numbers of them to adopt Islam. He also commenced the state-sponsored destruction of churches and synagogues, most famously the Church of the Holy Sepulchre. And yet, near the end, this same caliph relented, mitigating the severity of his previous policies. A general picture of what happened already exists, but the precise chronological order of these events and many of the exact details remain vague. Most importantly, we continue not to have a reason for his radically new policy. Al-Maqrīzī’s various accounts provide useful evidence although they hardly suffice. The Jewish reaction is far from clear. Two Christian histories, those by the Melkite Yaḥyā ibn Saʿīd of Antioch and the History of the Patriarchs of Alexandria, confirm many particulars. However none of this information explains why. Was al-Ḥākim moved to act as he did in response to, or in imitation of, the strikingly similar set of restrictive regulations imposed long before under the so-called “Pact of ʿUmar”?