At the beginning of his Ars medica , Galen enumerates three ways of imparting knowledge, the only ones (as he asserts) that follow a strict order. This claim gave rise to never-ending polemics in the Western Middle Ages with a discussion of what doctrina really means, juxtaposing Galens three ways with the four procedures in Aristotles Analytica posteriora. The controversy became virulent with the wide reception of the Commentum Hali, a translation from the Arabic by Gerard of Cremona ( 1187) of Alî ibn Ridwâns ( between 1061 and 1069) commentary on the Galenic Ars. While, from the 13th century onwards, the Commentum Hali marks a turning point as far as reflection on Galens ideas is concerned, the exchanges about Galens teachings are considerably older and were heated already in the context of the School of Alexandria at the beginning of the 6th century. According to the opinion of some scholars, it was here that Galens three modes were in opposition to the five methods to be used, both for teaching and for the acquisition of knowledge. Centuries later, Constantine the Africans (d. before 1098/1099) Pantegni transmitted the theory of the five methods to the Salernitan doctors of the 12th century, who also had access to a version of the Ars translated directly from the Greek. This was the reason why the Salernitans were constrained to resolve the conflicting positions that had already been discussed in Alexandria even before the Commentum Hali became known. This article analyzes the two oldest phases of this controversy, i. e. the first, which had developed in Alexandria and which is studied here with reference to recent work on the transmission from Greek to Arabic, and the second phase, at Salerno, drawing on texts by Master Bartholomew which have not been edited so far.