The Hadith Basis
The foundational hadith: “My community shall not agree on an error.” If the entire Muslim scholarly community agrees that something is true or required, that agreement itself is evidence — because God would not allow the whole community to be wrong simultaneously.
The implication: ijma’ is not infallible because the scholars are individually infallible, but because God guarantees the community’s collective reliability.
The Four Types
Ijma’ al-sahaba (consensus of the Companions): the highest form — if all the Companions agreed on a ruling, subsequent scholars treat this as incontrovertible. Example: the Companions agreed that the Quran should be compiled into a single text under Abu Bakr.
Ijma’ explicit/tacit (sarih/sukuti): explicit = all scholars stated their agreement. Tacit = the matter was presented and no one objected. Tacit ijma’ is weaker but still invoked.
Ijma’ of each generation: later generations of scholars can achieve ijma’ on questions that arose after the Companions — but their ijma’ carries less weight than the Companions’.
Ijma’ of the Four Schools: on questions where all four Sunni schools agree, the ruling is practically treated as settled — though theoretically this is not ijma’ but very strong precedent.
The Practical Problem
Achieving genuine ijma’ is almost impossible to verify:
- How do you poll all scholars simultaneously?
- What if a scholar disagreed but silently?
- What about scholars in remote regions who were never consulted?
For this reason, most invocations of ijma’ in classical fiqh are retrospective: “The scholars have agreed” means “everyone we know of agreed and no dissent was recorded.”
The Ismaili Perspective
In Ismaili jurisprudence, the living Imam holds the authority that the Sunni tradition attempts to locate in scholarly consensus. The Imam’s teaching is the living ijma’ — not a retrospective reconstruction but a present authority. The difficulty of achieving genuine scholarly consensus in the Sunni framework is, in Ismaili thought, precisely why God preserved the Imam: to prevent the community from disagreeing on fundamental matters of religion.
See also: Ilm Al Usul, Ilm Al Qiyas, Dai Al Mutlaq, Ismaili Dawat Organization, Sunna Al Nabawi, Nubuwwa Prophethood