In recent work in political philosophy there has been much discussion of two approaches to theorizing about justice that have come to be called ‘ideal theory’ and ‘non-ideal theory’. The distinction was originally articulated by Rawls, who defended his focus on ideal theory in terms of a supposed ‘priority’ of the latter over non-ideal theory. Many critics have rejected this claim of priority and in general have questioned the usefulness of ideal theory. In diagnosing the problem with ideal theory, they (...) have frequently fingered for blame the idealization it involves. In this paper I focus on one particular, much-discussed idealization—full compliance—in order to defend it. Focusing on the assumption, I argue that Rawls’s work is not ideal in the way that it is usually thought to be, is less ideal than is widely recognized, and became less ideal over time. I also argue that critics who in effect claim that it is not realistic enough simply fail to understand Rawls’s central motivation. Finally, I defend the assumption by arguing that there is an important sense in which all theories of justice must assume full compliance. Such an assumption, I argue, is needed if we are to have a plausible basis on which to judge the normative attractiveness of a theory. (shrink)