Hospice and Palliative Medicine is a relatively new medical specialty that treats patients who are suffering from uncontrolled symptoms or for whom the goals of medical care are ambiguous. These role sets frequently overlap for the chronically and terminally ill, patients whose care is not well managed by the logic of medical intervention that emphasizes both the maximization of longevity and the curing of illnesses. Considering this unique role and patient population, how do these kinds of physicians establish criteria of success, and how do they make this intelligible to their colleagues in other specialties to promote the work of HPM. And how do they do this when they are working at the discretion of skeptical and guarded colleagues? The internal structure of professional bodies has been treated as generic and unproblematic for understanding the inter-relations between different professional groups. With the growing functional differentiation within professions, understanding intra-professional collaboration and competition is needed. The sociology of Professions has been marked by an emphasis on the means by which different kinds of professionals dominate their areas of work to the exclusion of all competitors. This "turf model" emphasizes competition at the expense of collaboration, and the ready at hand theoretical alternatives to the turf model have traded pure competition for pure collaboration. These extreme theoretical alternatives are both motivated by a shared theoretical progenitor, ecology. In this dissertation I emphasize an ecological model of the professions by observing the different lines of influence that draw different professional bodies together and push them apart. To do this I advance a further theoretical innovation, ontology as a social theoretical device for understanding the small worlds individuals occupy. Functional differences cause cognitive, linguistic and practical differences between social groups that undermine their ability to successfully collaborate. Using the case study of Hospice and Palliative Medicine, I advance our understanding of the professions and organizations, and elaborate on how the work of these clinicians is completed despite the professional circumstances that promote failure at the expense of success.