The cathedral ceiling located in the entrance hall of the Montreal Neurological Institute, planned by its founder Wilder Penfield, has intrigued visitors since it was erected in 1934. Central to its charm is a cryptic comment by the ancient physician Galen of Pergamum, which refutes a dire Hippocratic aphorism about prognosis in brain injury. Galen's optimism, shared by Penfield, is curious from a fellow ancient. In this article, we use primary sources in Ancient Greek as well as secondary sources to not only examine the origins of Galen's epistemology but also, using a methodology in classics scholarship known as reception studies, illustrate how an awareness of this ancient debate can illuminate contemporary clinical contexts. While Galen based his prognostications on direct clinical observations like the Hippocratics, he also engaged in experimental and anatomic work in both animals and humans, which informed his views on neurologic states and outcomes. Penfield's memorialization of Galen is representative of the evolution of the neurosciences and the ongoing importance of evidence-based prognostication in severe brain injury.