How do individuals think and behave? In other words, what does it mean for them to be rational? Answering this question requires some preliminary grounding in rational choice theory, and so I begin the chapter with a brief tour of it before contrasting the economizing and legitimizing perspectives that describe rationality, respectively, under the institutional collective action and sociocultural collective action frameworks. Second, what is the nature of the relationship of the individual to institutions? To answer this question, I define institutions, and then distinguish between institutional mediation versus institutional embeddedness.