disregarding every other possible route of transmission—whether the correct view lies with him, with the opposing scholar, or with both of them according to those who maintain that “every mujtahid is correct.”

There are several causes for this:

• One is that the very narrator of the report is considered weak by one scholar while the other regards him as trustworthy. The science of evaluating transmitters is vast. At times the scholar who declares him weak may indeed be right because he knows of a flaw that undermines the narrator; at other times the truth may be with the one who declares him reliable because he realizes that the alleged flaw is not actually discrediting—either because that type of flaw is not harmful in principle, or because the narrator had an excuse that neutralizes the criticism. This, too, is a broad field.

Among the experts in narrator criticism there is both consensus and disagreement on such matters, just as specialists in every other discipline concur and differ within their own sciences.

• Another cause is that one scholar does not believe the narrator actually heard the ḥadith from the authority he names, whereas another scholar is convinced that he did, on the basis of well-known reasons that warrant such a conclusion.

• Yet another cause is that a narrator may have two distinct periods: one of soundness and another of confusion—for example, after becoming senile or after his books were lost in a fire. Whatever he related during his sound period is authentic, whereas what he narrated during his confused period is weak; yet it may be unclear to which period a given ḥadith belongs.