sound innate reason determines, because it is internal evidence just as the Prophet is external evidence. Or else, one should follow what has been established by the infal‌ lible leaders-the Prophet and the Imams-since they are the authorities in matters of religion. They are also the ones about whom the Prophet has•left his last will and testament, requiring the Muslims to adhere to them. Thus he declared, "I leave among you two things of high esteem: the Book of God and my family, my ahl fll-bayt. As long as you adhere to them both, you will never go astray, ever."١
There is no doubt about the certainty of their opinion if it is established through a
reliable source of transmission that is not open to doubt, just as there is no doubt about the absence of its certainty if it is proven that it was transmitted through a weak tradition that does not meet the conditions for its admission as evidence. Is it pos‌ sible to establish an authentic proof by means of evidence derived through conjec‌ ture? There is a dispute in this matter among the scholars.
The problem can be stated as follows:
The question rests on the dispute about the evidential nature of a reliable single tradition (khabar al-wal:zid al-thiqa), related from the infallible Imams, explaining the Quran. The point of the dispute is that the evidentiary nature that is admitted for a single tradition, or for any other conjectural proof, requires that actions should be based on [these traditions or conjectures] when the true state of affairs is unknown, just as they would be based on the true state of affairs if it were known with cer‌ tainty. This corollary is not realized except when the underlying idea of communica‌ tion is a religious-legal ordinance, or a question on which the lawgiver has constructed such an ordinance. This condition may not be available in a single tradition that is related on the authority of the infallible Imams in regard to the exegesis of the Quran.
The response to the problem can be formulated as follows:
This objection is without substantiation. We explained, in our discussion of the science of legal theory, that the meaning of the evidentiary admission of a documen‌ tation, in matters that function as indicators of the true state of affairs, is their ad‌ vancement to the level of ascertainment by means of an injunction from the lawgiver. Accordingly, the considered method would be one of the several ways to certainty. But it is the way that is based on obedience to the injunction of the lawgiver, rather than on reasoning. Hence, all that can be derived from the reliable documentation among the transmitted sources can also be derived from this conjectural source. The traditions are authenticated when they are in conformity with it, just as they become authenticated by means of mental knowledge. In any case, it is not an opinion formed without certainty.
This is corroborated by the practice that is common among rational persons. The reason [for this corroboration] is that they treat the reliable method as they do men‌ tal knowledge, without differentiating between their effects. Thus, the hand, for ex‌ ample, among rational persons, is a symbol of ownership for the person to whom the hand belongs when he has something in his hand. It is on the basis of this that they assign to him the effect of ownership and inform about his being an owner of a thing, with no one rejecting [the claim]. There is no evidence from the direction of the law‌ giver that prohibits this continuous rational method.
Indeed, the crucial factor that is taken into consideration in a reliable tradition, and in other acceptable methods [of transmission], is that they should meet all the