The Question
In Shia theology, isma is the divinely conferred immunity from sin and error that distinguishes the Prophets and the Imams from ordinary believers. It is one of the load-bearing concepts of the doctrine of the Imamate: because the Imam is the appointed guide after the Prophet, his guidance must be trustworthy without qualification, and that trustworthiness is grounded in his being ma’sum (divinely protected). On this much, Twelver (Ithna Ashari) and Ismaili Shi’ism agree. Both traditions hold that the Imam of the age is infallible and that obedience to him is bound up with walayah (loving allegiance to the rightful authority).
What is actually disputed is narrower and more interesting: what does isma require in practice, and how is it to be recognized in the historical conduct of an Imam? If an Imam is infallible, does that mean his every outward political act must appear flawless to an external observer — or does isma attach primarily to his authoritative religious guidance, leaving room for the compromises that governing a real state imposes? The two traditions answer differently, and because the Ismaili line passes through the Fatimid caliph-imams, who actually held worldly power, the question becomes concrete in a way it does not for the largely quietist or hidden Twelver Imams. The debate matters because it is not only about history; it is about how infallibility is theorized in the first place.
The Twelver Critique
The Twelver critique, set out in Ali Azhar Arastu’s booklet Examining the Ismaili Imams and the Bohras (published by the World Islamic Network and hosted on al-Islam.org, from an explicitly Twelver standpoint), proceeds from a strong reading of isma: an infallible Imam can neither sin nor commit error, in private or in public, and any well-attested instance of sinful or erroneous conduct would therefore disqualify a claimant from the Imamate. On this premise the booklet contends that aspects of the Fatimid record cannot be reconciled with infallibility. It points to political accommodations, reversals of policy, and above all to the contested conduct ascribed to al-Hakim bi-Amr Allah (r. 996–1021) — the harsh and sometimes erratic measures reported of him — as evidence that the men the Ismailis venerate as ma’sum Imams did not in fact display the conduct infallibility requires.
The argument is thus partly historical and partly definitional. Historically, it marshals reports of contested behaviour; definitionally, it insists that isma must mean an observable, uniform perfection of action, so that the burden falls on the Ismailis to show that their Imams met that standard. It should be noted that the most damaging of the historical reports it draws upon — the image of al-Hakim as a “mad caliph,” for example — are themselves drawn largely from hostile or later sources, a point the scholarly assessment below takes up.
The Ismaili-Tayyibi Response
The Ismaili-Tayyibi tradition states isma within its own theology of the Imamate rather than as a simple checklist of outward acts. The Imam is held to be the living, speaking locus of divine guidance for his age — the natiq of ta’wil, the one in whom the inner meaning (batin) of revelation is vested. His infallibility, on this understanding, guarantees the soundness of the guidance he transmits and the walayah owed to him; it is inseparable from his rank within the cosmic hierarchy of the hudud al-din, the graded “limits” or ranks of religion through which divine knowledge descends to the community. Within this framework, the outward (zahir) acts of an Imam who also rules a state are not the measure of his isma but an arena in which his guidance is exercised under real constraints.
Accordingly, the tradition reads the Fatimid record through the relation of zahir and batin. The political compromises of rule — alliances, concealment (taqiyya), reversals demanded by circumstance — are seen as the prudent governance of a ma’sum Imam acting in a fallen world, not as lapses in his protected guidance. Conduct that an outside observer finds opaque is, on this view, precisely the kind of thing whose inner wisdom is accessible through ta’wil. Isma, then, is not a promise that an Imam will behave indistinguishably from any pious private person; it is the guarantee that his teaching authority and his transmission of divine knowledge are free from error. The Bohra tradition holds that the critique mistakes a demand for uniform worldly behaviour for the doctrine itself.
Scholarly Assessment
Mainstream academic historians tend to treat the sharpest factual premises of the critique as contested rather than settled. Farhad Daftary, in his standard history of the Ismailis, and Heinz Halm, in his studies of the Fatimid state, both caution that the lurid “mad caliph” portrait of al-Hakim derives heavily from hostile, later, or anti-Fatimid sources and is not a neutral record of his reign; Halm in particular reconstructs a more complex and politically intelligible ruler. Wilferd Madelung’s work on early Shia and Ismaili doctrine similarly frames isma as a theological concept that developed and was theorized differently across the Shia schools, rather than a single fixed yardstick against which dynasties can be simply scored. Scholars also note that the “slave-girl” genealogy argument against the Fatimids and the informer story about Muhammad ibn Isma’il are polemical motifs of long standing whose historicity is doubtful. The fair academic conclusion is that the dispute is as much doctrinal as historical: the two traditions affirm isma but build it into different theologies of the Imamate, and several of the historical charges used to press the critique are not facts that scholarship has established.
See also: Scholarly Debates Overview, Al Hakim Bi Amr Allah Assessment, Ismaili Cosmology Hudud Al Din, Bayah And Walayah, Imam And Salvation Debate