of the Ashʿarīs, such as Abū Isḥāq and Ibn Fūrak. Ibn al-Bāqillānī, however, was the one who rejected this view, and he was followed by Abū al-Maʿālī, Abū Ḥāmid, Ibn ʿAqīl, Ibn al-Jawzī, Ibn al-Khaṭīb, al-Āmidī and their likes. The first position is the one recorded by Shaykh Abū Ḥāmid, Abū al-Ṭayyib, Abū Isḥāq and other leading Shāfiʿīs; it is likewise set down by Qāḍī ʿAbd al-Wahhāb and other Mālikīs, by Abū Yaʿlā, Abū al-Khaṭṭāb, Abū al-Ḥasan Ibn al-Zāghūnī and their fellow Ḥanbalīs, and by Shams al-Dīn al-Sarakh­sī and other Ḥanafīs.

Now, if a consensus that a report is truthful produces certainty regarding it, the point of reference for that consensus must be the agreement of the scholars of hadith—just as, in matters of law, consensus is assessed by the agreement of those qualified in what is forbidden, obligatory, or permissible.

The point at issue here is that when several independent chains exist with no evidence of collusion—something normally impossible to arrange—they yield knowledge of the substance transmitted. This principle is especially useful in the discipline that investigates the conditions of the transmitters. In such cases, the narration of an unknown narrator, one with poor retention, a mursal report, and the like, can all be of benefit. For that reason the scholars would record such narrations and say, “They are suitable for corroboration and comparison, though not for independent proof.” Aḥmad said, “I may write down a man’s ḥadīth so that I can compare it.”

The same applies to ʿAbd Allāh ibn Lahīʿa, the judge of Egypt: he was among the most prolific transmitters and one of the finest of men, but after his books were burned errors found their way into his later narrations. Consequently, his reports are now used for corroboration and supportive citation. He is often mentioned alongside al-Layth ibn Saʿd, whereas al-Layth is a firmly established, authoritative imām.

Just as they use the ḥadīth of someone with weak memory for corroboration, they also declare certain parts of a trustworthy, upright, precise narrator’s ḥadīth to be weak when clear indicators show that he erred in those particulars. They deduce this from various clues, and they call this discipline “ʿilm ʿilal al-ḥadīth” (the science of hidden defects in hadith).