This book provides a critical edition as well as a French translation of the Doubts About Galen, a polemical treatise written by Abū Bakr al-Rāzī, one of the most innovative clinicians and philosophers of the Arabo-Islamic Middle Ages. His Doubts stand at the cross-roads of metaphysics, natural philosophy and medicine. The edition includes a comprehensive introduction which discusses the treatise’ most significant philosophical features.