This paper takes up ancient holism as a significant problem in ancient Greek medicine and philosophy that has to be approached with a critical awareness of modern receptions of ancient Greek medicine and science as naively vitalist, and of ancient Greece, more broadly, as the site of a pure, unified form of life. I argue that viewing questions of part and whole within the living being from the perspective of sympathy (sumpatheia) can help us articulate the major conceptual axes operative within ancient holism as a problem. I begin by situating the inquiry into ancient holism both in relationship to a history of scholarship on ancient Greek medicine and science that has focused on cultural and historical difference, and in relationship to the contested status of ancient, or premodern, 'life' within continental philosophy. I then turn to the two major axes that I argue help to structure the conceptual field of sympathy as it develops from the late fourth and early third century BCE in learned medicine and philosophical psychology. I focus on the development of sympathy in the Stoics, the Epicureans, and Galen, while also considering the theorization of living beings in the Hippocratics, Plato, and Aristotle. The first axis moves from 'part-to-part' sympathy to 'part-to-whole' sympathy; the second from the sympathy of body and soul to a sympathy that encompasses all the parts of the living thing. Following these axes helps us identify, in turn, persistent questions about the material structure of the body that allows for the communication of affections between its parts but also its coordinated work as a living whole. It also focuses attention on what guarantees the unity of the whole over and above that structure. Through tracking sympathy as both the occurrence of co-affection between the parts of a living thing and the relationship enabling that occurrence, we can gain insight into the theorization of a living being as a dynamic and complex but unified whole in the centuries after Aristotle.