This book presents the first critical edition and translation into a European language of a text that has been largely overlooked by scholars: the Solution to the Doubts about Galen, by Ab? al-?Al?? ibn Zuhr, a physician dwelling in twelfth-century al-Andalus. He composed it to defend Galen against Ab? Bakr al-R?z?'s (d. 925) attacks in his Doubts about Galen (published in the same series). The Solution is of threefold interest: firstly, regarding Graeco-Arabic studies, it includes numerous testimonies of treatises by Galen of Pergamum (129-c. 216 CE) lost in Arabic, but also sometimes in Greek. The most famous of these lost texts is without a doubt Galen's most important logical treatise, On Demonstration. The Solution is thereby a veritable goldmine for Graeco-Arabic studies and our reconstruction of the Arabic Galen. Secondly, even though Ab? al-?Al??was a physician more than he was a philosopher, his answers to R?z? contribute to our understanding of the history of Islamicate philosophy: they provide access to several arguments circulating in the twelfth century on topics related to epistemology and natural philosophy, such as the existence of the void, for example. Finally, Ab? al-?Al?? includes colorful - and pitiless - comments on the medical milieu of his time. The book will be useful for students and scholars of ancient and medieval medicine and philosophy, as well as those engaged in the study of the classical world, Graeco-Arabic studies or Islamic studies.