considers him weak because he knows of grounds for impugning his reliability. Yet the other scholar may be correct because he knows that those grounds do not warrant such criticism—either because they are not inherently discrediting, or because the narrator had an excuse that precludes criticism in that instance. This is a vast field. Scholars of narrators and their circumstances have areas of agreement and disagreement, just as other scholars do within their respective disciplines.

Another reason is that one scholar may not believe that a narrator heard the hadith from the person on whose authority he relates it, while another believes that he did, on well-known grounds that establish this.

Another reason is that a narrator may have experienced two periods: one of sound transmission and another of unreliable transmission, as when his memory becomes confused or his books are destroyed by fire. What he transmitted during the period of sound transmission is authentic, while what he transmitted during the period of unreliable transmission is weak. One scholar may not know to which category a particular hadith belongs, while another knows that it was transmitted during the period of sound transmission.

Another reason is that a narrator may have forgotten the hadith and been unable to recall it later, or denied having transmitted it. One scholar considers this a defect requiring that the hadith be rejected, whereas another holds that it may validly be cited as evidence. This is a well-known issue.

Another reason is that many scholars of the Hijaz hold that a hadith transmitted by an Iraqi or Syrian narrator should not be accepted as authoritative evidence unless it has a basis in the Hijaz. Indeed, one of them went so far as to say: “Treat the hadiths