One of the disputed and challenging issues is the subject of taqlid of the most learned Mujtahid. Taqlid in legal parlance means following the most knowledgeable jurist. The controversy revolves around the necessity of following or not following the most learned scholars. Also, when it comes to being the most learned (aʿlamiyya) of jurists, does the presence of the criterion suffice or is it necessary that the most learned and the less learned Mujtahids should be so different in terms of knowledge and understanding and that the saying of the less learned should not be deemed authoritative. Jurists have discussed this issue in terms of religious obligation but scientific qualification as a subject-matter has not been scrutinized or has been investigated but very little. This study, which is presented with the intention of commemorating the great scholar of Uṣūl, al-Shaykh Murtaḍa al-Ḥāʾiri (ra), consists of two parts. The first part deals mainly with criticizing his theory which states that following the most learned Mujtahid is not necessary. His objections and arguments have been discussed and rejected and finally the necessity of following the most learned Mujtahid has been established and it has been argued that in the event that one knows that the most learned Mujtahid and the less learned differ in their opinion about a given issue, it is obligatory to follow the most learned Mujtahid. The second part deals with the application of different principles to conflicts and it has been established that following the most learned Mujtahid is obligatory only when the gap between the most learned and the less learned is so wide and unbridgeable that, in common view, the saying of the less learned is not deemed a manifestation of a legal proof.