This study examines in detail the basis of al-Shafi`i's arguments for the supremacy of oral tradition over communal legal practice. It concentrates on one broad issue, the definition of `ilm (knowledge) and one technical issue, the problem of authenticating a particular khabar (oral tradition or report, plural akhbar, ) and its binding nature, especially a report of the category known as the specialists' report (khabar al-khassa). On the first issue, this study examines the concept of knowledge based on reports (`ilm al-khabar) because it had an important influence on al-Shafi`i. This is followed by a detailed account of al-Shafi`i's own discussion of `ilm. It brings out clearly that al-Shafi`i means religious law when discussing `ilm. It also shows how knowledge of religious law can be obtained. Al-Shafi`i's approach is to restrict the argument to knowledge of specialised and debatable points, rather than what is generally accepted. He seeks to prove the indispensability in this area of specialists' knowledge of reliable documentation external to the law itself. The following chapter deals with the question of authenticating a khabar from the Prophet (a hadith), not as purely technical question but within a polemical context in which the practical difficulty of authenticating a khabar was used by those opposed to the intellectual dominance of oral tradition as a reason not to use the khabar. In the final chapter al- Shaf i's arguments with two identifiable schools of opposing thought, ahl al-kaläm and ahl al-figh, are examined in detail. The thesis as a whole gives a significant insight into the efficacy and durability of al-Shafi`i's arguments, not so much by defeating his opponents' arguments but by buttressing those of the defenders and advocates of oral tradition.