This interpretation and commentary of the first book of Augustine's earliest extant work Contra Academicos establishes for the first time a close relationship between the topicalisation of various methods for imparting knowledge in the first book of the dialogue (reading, conversation, divination) and the argument with the sceptics. The disputed role of Cicero's protreptic dialogue Hortensius as a reference text is clarified. The commentary furnishes detailed analyses of the argumentative structure and a wealth of information on philological, historical and philosophical issues.