PHILOSOPHICAL METHOD OF DIOSCORIDES ’ S DE MATERIA MEDICA Marina Marren and Kevin Marren It is commonly thought that Dioscorides ’ s view on medicine is purely pragmatic, focused entirely on the effectiveness of medicines, and derived from trial and error. One reason for this interpretation is that Dioscorides himself wrote little about his theory of medicine. In this article, however, we argue that he would have arranged De Materia Medica in a way that would have been useful only to a skilled practitioner. This argument implies that Dioscorides had a medical theory, as the arrangement of the content could not have fol- lowed a trial-and-error approach. It is only in the sense of having a theory that he is able to claim that his text is more “ complete” than others. This article provides a historical over- view of the text from its genesis to its reception and, ultimately, to its falling out of use. This article concludes with a series of hypotheses on the correspondence between theory and arrangement of the treatise, with the aim of narrowing scholarly conjectures about both. In the final analysis, we argue that an arrangement by family resemblance most closely corresponds to the theory that animates Dioscorides’ s text. 1. Introduction The purpose of this article is to offer a speculative reconstruction of the principles or theory guiding the original arrangement of medicines in Dioscorides ’ s De Ma- teria Medica. Dioscorides himself makes no thorough statement of his theory of medicine. He even disparages others who give causal accounts and who presum- ably rely on theory more than practice. And yet, as a practical work, De Materia Medica cannot be completely devoid of theory. According to Vivian Nutton (2012), Dioscorides’ s “ aim was to provide as complete a listing of medicinal Contact the corresponding author, Marina Marren (mmarren@uaeu.ac.ae), at United Arab Emir- ates University, United Arab Emirates. We thank our anonymous reviewers for their careful attention to our work and numerous excellent recommendations, which helped improve the article in many ways. Electronically published March 10, 2023. HOPOS: The Journal of the International Society for the History of Philosophy of Science, volume 13, number 1, Spring 2023. © 2023 International Society for the History of Philosophy of Science. All rights reserved. Published by The University of Chicago Press for the International Society for the History of Philosophy of Science. https://doi .org/10.1086/724061 180