This thesis offers an interpretation of the ontology associated with Medicinal Plants as displayed in Pliny the Elder’s Natural History. The goal of this study, broadly speaking, was to provide new ways of thinking about medicine by paying attention to old ways of thinking about medicine; narrowing the study of Pliny’s work to the vegetal specifically gave a necessary focal point in an otherwise too expansive field, while not closing off the possibility of extrapolating conclusions about medicine beyond either Plants or even Pliny. The unique array of medical and ontological ideas convened by Pliny are both distant enough temporally, and different enough practically and philosophically, to stimulate thought and beg for questions to be asked. At the same time, similarity has been found not to be lacking between medical thought then and now, which suggests the tenability of comparing two snapshots of Western medicine. The main finding of this thesis is that transparency regarding what medicine is, does, and where it comes from is often segregated, and sometimes forgotten altogether, in the pursuit of health as a subject now sterilized from philosophy. A practical recommendation based on this finding is that the Medical Humanities may offer a much-needed bridge between the now otherwise divergent fields of philosophy and medicine. The implications for medical education and practice of a human society more curious of its own medical history are far-reaching and could only begin to be touched upon in this thesis. An overall statement can be made however, that philosophy needs to once again more fully permeate medicine as it seems to have in 1st century Rome.