Galen had an abiding reverence for the classicized Greek poets of his day, in keeping with the prevailing cultural norms of the educated elite. He wrote monographic works on Attic comedy, and often peppered his medical treatises (particularly the psychological and propaedeutic works) with quotations from Homer, the Greek lyric poets and the tragedians. But while he regarded the study of poetry as essential for a complete education, however nebulously construed, he was conflicted about its utility for the scientific enterprise. Often in On the Opinions of Hippocrates and Plato (Plac. Hipp. Plat.), for example, Galen ridicules the Stoic Chrysippus for misusing the testimony of poets in the service of philosophical and scientific argument, while elsewhere in the treatise he freely cites classic poets as illustrative of his own arguments. In Protrepicus, too, he includes mousikē (encompassing for Galen something like our notion of ‘the literary’) as one of the ‘elevated arts’ (semnai tekhnai), the cultivation of which will help humans live according to truth and reason. This paper will examine Galen’s complicated, often inconsistent, attitude to the role of ‘literature’ in his work, focusing specifically on questions of poetic vs. logical/philosophical authority. In particular, I will discuss how Galen aligns his own practice of invoking poetic authors as evidence or exempla with Plato’s, and attempt to clarify what he believed literary testimony could contribute to his argument, both rhetorically and philosophically.