Human agency has proven to be a contested issue in development research and practice. Although economics has been the most influential discipline, increasingly different accounts highlight distinct features of human beings and the contexts they inhabit, which lead to different implications. This article seeks to delineate the boundaries of the discussion and map out what are arguably the main alternatives within the field. Since such discussion deals with the question of what human action is, the argument is elaborated from the philosophy of science. Contra convention, the discussion uses a philosophical ontology, which is concerned with out connection to the world. Jackson’s heuristic is adopted to generate four philosophies of science and four notions of agency, regarded as ideal typical. Neopositivism advances a rational agent, reflexivity suggests a patient, critical realism furthers an interagent, and analyticism proposes a transagent. This article invites scholars and practitioners interested in this increasingly interdisciplinary area to raise their awareness regarding the foundations on which their ideas about human agency build and note the implications they have for the production and consumption of knowledge.