Reading Middle Ages in terms of the history of man’s education – made possible by merging Patristics and Scholastics – the present paper focuses on interpreting Thomas Aquinas’ De Magistro with the aim to show how, in this treatise, the problem of human knowledge moves from an epistemological to a pedagogical level, in so opening the question of the formal autonomy of the knowledgeable subject. If the teacher, through his/her teaching, stimulates the student to learn, the latter in turn is able to know autonomously, even without the help of the teacher, and this knowing involves an independent, personal and free use of the intellect. The paper points out, therefore, that the De Magistro is not to be seen as a simple treatise on teaching since, behind the didactic problem, it hides a much deeper epistemological and pedagogical issue that contributes to prepare the transition from the perfectio of the Latin language to the Bildung of the Mittelhochdeutsch.