Efforts within organized medicine over the last twenty years to reestablish an ethic of professionalism have obscured the fact that currently there are several competing clusters or types of medical professionalism, each of which represents a unique approach to medical work. Stated differently, the "professionalism" that has emerged within the academic medical journals, conferences, debates, and discussions over the past twenty years is a highly selective and privileged narrative, developed and delivered by one, possibly two, particular strata within the organizational structure of medicine. We call this strata the ruling class of medicine, and we refer to its medical professionalism as nostalgic. The other clusters of medical professionalism that we empirically "discovered" include entrepreneurial, empirical, lifestyle, unreflective, academic, and activist professionalism. The development of this seven-cluster system of medical professionalism was by no means an accident. Instead, it was the direct result of our involvement in the new science of complexity (e.g., Axelrod, 1997; Bak, 1999; Capra, 1996; Cilliers, 1998; Holland, 1998). Specifically, we are in the process of developing our own theoretical and methodological framework, which we applied to the current study. The purpose of this chapter is to introduce readers to a more "complex" medical professionalism. To do so, we begin with a quick overview of the theory and method we developed, along with the historical archive we used to conduct our empirical analyses. Next, we review the five important ways the theory and method helped us to recognize, discover, analyze and assemble medical professionalism as a complex social system, including a thick description of the seven clusters we discovered. We conclude by putting the complex social system of medical professionalism together, reflecting on the insights our results have for the future teaching and evaluation of professionalism.