In the past decade, the value of so-called ideal theory has become a major point of dispute among political theorists. While critics of ideal theory accuse this approach of “idle utopianism”, its advocates fault the critics for conceding to “cynical realism”.

This dissertation examines two charges against ideal theory. The demandingness charge states that ideal theory fails to acknowledge the constraints on justice set by the empirical conditions that prevail in our world, and that it therefore produces invalid principles. The uselessness charge states that ideal theory, even if it tells us what justice would require under exceptionally favorable circumstances, offers no information valuable for guiding action in the nonideal circumstances characteristic of today’s societies. The two charges target the idealized assumptions made in ideal theory, in particular the assumption of full compliance. By assuming full compliance, the critics argue, ideal theory ignores the way real-world agents’ motivational limitations render the pursuit of its proposed principles infeasible or undesirable.

In four free-standing articles, I examine when and why noncompliance due to motivational limitations puts constraints on justice, and how this affects the status and usefulness of ideal theory. I argue that motivational limitations constrain justice in ideal theory if we hold that justice is action-guiding in the sense that it confers actual duties on individual agents, and that the distribution of collective duties to individuals requires reasonable expectations of others’ compliance. In nonideal theory, adopting an actualist standpoint will lead us to conclude that not only the noncompliance of others, but also our own foreseeable noncompliance constrains what justice can demand. I further argue that how this affects the usefulness of ideal theory depends, on the one hand, on how we interpret crucial concepts such as “action-guidance”, and, on the other, on which task we expect political theory to perform. My findings shed new light over the complex conflict lines that underlie the current dispute, and urge debaters to render explicit and argue for the assumptions upon which they rest their judgments about ideal theory.