Rawls ignited a debate in political theory when he introduced a division betweenthe ideal and nonideal parts of a theory of justice. In the ideal part of thetheory, one presents a positive conception of justice in a setting that assumesperfect compliance with the rules of justice. In the nonideal part, oneaddresses the question of what happens under departures from compliance. Criticsof Rawls have attacked his focus on ideal theory as a form of utopianism, andhave argued that political theory should be focused instead on providingsolutions to the manifest injustices of the real world. In this essay, I offer adefense of the ideal/nonideal theory distinction according to which it amountsto nothing more than a division of labor, and explore some scientific analogies.Rawls’s own focus on the ideal part of the theory, I argue, stemsfrom a felt need to clarify the foundations of justice, rather than a utopianneglect of real world problems.