The essay agues that there is little scope for ideal theory in politicalphilosophy, even under Rawls’s conception of its aims. It begins byidentifying features of a standard example of ideal theory in physics— the ideal gas law, PV=NRT and draws attention to thelack of these features in Rawls’s derivation of the principles ofjustice from the original position. A. John Simmons’s defense ofideal theory against criticisms of Amartya Sen is examined, as are furthercriticisms of both by David Schmidtz. The essay goes on to develop a conceptionof the domain of social relations to be characterized by justice that suggeststhat as a moving target it makes ideal theory otiose. Examination ofRawls’s later views substantiate the conclusion that ideal theory aspropounded in A Theory of Justice is a mistaken starting point in the enterpriseof political philosophy. Differences between the domains of ideal theory inmathematics, physics, and economics on the one hand, and political philosophy onthe other, reinforce this conclusion.
