ʿIṣma — Prophetic and Imamic Infallibility

The Prophet's statements in his prophetic capacity are infallible because they are revelation — divinely protected at the channel, not merely through human moral effort. Q 53:3–4 establishes ʿiṣmat al-anbiyāʾ (prophetic infallibility) as a Quranic given, accepted across all schools. The cross-school dispute is not over this but over: (a) whether minor non-prophetic slips are possible; (b) whether the Imams share prophetic ʿiṣma.

Q 33:33 combined with the Ḥadīth al-Kisāʾ (confirmed in Ṣaḥīḥ Muslim) establishes the ʿiṣma of the Five: the Prophet, Imam ʿAlī, Fāṭima, Imam al-Ḥasan, and Imam al-Ḥusayn. The Sunni counter-argument (the verse addresses the Prophet's wives) is refuted by: (a) the Kisāʾ hadith explicitly limits the Ahl al-Bayt designation to the Five in this context; (b) the grammatical shift to masculine plural in Q 33:33b; (c) the presence of the verse in a chapter whose context includes both the wives and the extended Ahl al-Bayt.

ʿIṣma is a rational necessity for the Imam's function as ḥujja. The argument from rational necessity is independent of the textual proofs (Q 33:33, Kisāʾ): even if one disputed those texts, reason establishes that a ḥujja who can err provides no certainty of guidance and therefore fails its defining function. The Sunni objection — "only Prophets have ʿiṣma because only they receive revelation" — misidentifies the basis: ʿiṣma is grounded in the ḥujja function, not in receiving new revelation. An Imam who interprets the final revelation without ʿiṣma may build the entire community's practice on a corrupted foundation.

The Imam's ʿiṣma is grounded in ʿilm ladunnī (God-bestowed knowledge). The chain: God bestows knowledge directly → the Imam knows the divine command with certainty → certainty eliminates the ground for error → ʿiṣma follows as a consequence of the type of knowledge possessed. This distinguishes the Imami claim from any assertion that the Imam is humanly infallible: the infallibility is not a human achievement but a consequence of the type of knowledge divinely given to the ḥujja.

The cross-school consensus on prophetic ʿiṣma in conveying revelation is the common starting point. The Imami school extends this to comprehensive ʿiṣma from birth in all acts and extends ʿiṣma to the Imams — based on the ḥujja function argument. The Ashʿarī and Māturīdī limitations reflect their view that guidance does not require a humanly infallible interpreter after the Prophet — the Quran and Sunna (mediated through scholarly ijtihad) are sufficient. The Imami counter: scholarly ijtihad on corrupted foundations produces corrupted output; the ḥujja is needed to guarantee the foundation.

ʿIṣma is voluntary, not compelled. The Imam's infallibility is the highest actualization of creaturely freedom — he has exercised his free will so completely in the direction of divine will that the two coincide. This connects to Ṣadrā's Four Journeys: the Perfect Man who has completed the Four Journeys has his will fully merged with divine will; ʿiṣma is the moral expression of this metaphysical achievement, not its override. The Imam's moral excellence is therefore real and admirable — not the "empty" perfection of a being who could not have done otherwise.