Our approach in this volume is both epistemological and comparative. We are raising two types of questions. Since we are historians working on textual sources written in different languages, we are first of all engaging in comparisons, and raising questions about the validity of a comparative approach to classical medicine: ‘What are the relevant intellectual parallels and the possible historical connections between, for example, Āyurvedic medicine in India and Galenism in the West?’ This contribution to the debate is based on the historical evidence we have of extensive intellectual exchanges between India and the West in the first centuries of the common era. Although the detailed evidence must be kept in the background, the following pages will expose two features that relate Āyurveda with Galenism. The first section, which deals with stylistic and rhetorical features of medical Sanskrit texts, will describe an Indian version of scholasticism, comparable on many points with medical Galenism. Another feature common to both scholarly traditions is humoralism. But a comparative study of the humoral theory is dependent upon a second type of question that bears upon the ways knowledge is established and put into practice: ‘What are the criteria for regarding a given aetiology, diagnosis, or prognosis as valid in Āyurvedic medicine, or any other scholarly tradition for that matter, and, in therapeutics, what are the criteria for efficacy?’ I shall first address the question of knowledge and experience in the context of a classical tradition, emphasizing the role of language. Then, pursuing one concrete example, the aetiology and therapeutics of epilepsy, I expound some key concepts of Āyurveda that revolve around the themes of rationality, truth and efficacy.