This paper explores Elinor Ostrom's account of practical reason through the conceptual lens provided by a typology of dimensions of rational conduct advanced by Amartya Sen. On Sen's view, self-interested behaviour has three independent, and separable, features: self-centred welfare, self-welfare goal and self-goal choice. We suggest that Ostrom is committed to a version of rational choice theory that retains the assumptions of self-welfare goal and self-goal choice but, by acknowledging that people's welfare is affected by factors beyond their material consumption, departs from the assumption of self-welfare goal. We argue that this departure is not necessarily driven by an acknowledgement, along Senian lines, that people may have reasons for action other than the single-minded pursuit of their own goals, but rather by Ostrom's belief that the decision problem people face is so complex that maximising behaviour is rendered impossible. We illustrate this argument by analysing how Elinor Ostrom's position differs not only from Sen's but also from that of her husband and long-time collaborator Vincent Ostrom, who in his analysis of the covenantal aspects of rule-making seems to depart from the assumptions of instrumental rationality and preference-satisfaction.