How Shaykh Ṭūsī Encountered the Discourse of Mufīd and Murtaḍā on the " Validity of an Isolated Tradition"

From the age of Shaykh Mufīd (d. 413) up to Muḥaqqiq Ḥillī (d. 676), we have witnessed an approach within the Imāmiyya discourse, which, by non-acceptance of traditions narrated by a single sources (āḥād), suffices with traditions narrated by several sources (mutawātir) and wrapped in evidences. In the meantime, Shakh Ṭūsī has not only considered as valid the āḥād traditions in his book, Al-‘Udda fī Uṣūl al-Fiqh, but has also claimed consensus in this respect, a claim that is in contradiction to the consensus claimed by Sayyid Murtaḍā. To resolve this contradiction various patterns have been presented by the Imāmiyya scholars. A brief look at the collected works of Shaykh Ṭūsī indicates that he too has not been committed to his claimed consensus and has preferred the view of invalidity of the āḥād traditions in most of his works. Such evidences suggest that instead of interpreting the discourse of Sayyid Murtaḍā, one should turn to a new explanation of Shaykh Ṭūsī’s view about the way to encounter āḥād traditions. It seems that Ṭūsī is also within discourse of Mufīd and Murtaḍā. Since his masters’ approach would result in putting aside a great part of the sunna and therefore turning to the verdict of intellect and scholarly principles, he has presented a new version of “principality of evidences school” (Mufīd’s and Murtaḍā’s school) so that by relying on it to make some development in accepting traditions.