Having completed the main defense of the two principles of justice, part ii of A Theory of Justice aims to “illustrate the content of the principles of justice.” (TJ, 195/171) The principles do not require a single institutional scheme for all circumstances, so any application needs to be sensitive to the conditions in which the principles are to be applied. This often requires that we rely on the specialized empirical knowledge that can be provided by economists, sociologists, and political scientists, among others. Philosophers have no particular expertise in these areas and so the design of institutions and policies is a quintessentially interdisciplinary task. Although the principles identify the standards and the ideals on the basis of which institutions and policies should be assessed, there is often a great deal of controversy about which designs and policies will, in fact, best live up to and satisfy these standards.

Rawls, therefore, is hesitant to consider in much detail the application of the principles to concrete circumstances, and he stresses that arrangements other than the ones he describes may also be just. Nonetheless, it is important to illustrate an institutional scheme that may plausibly be thought to realize the two principles. This is for three main reasons. First, the task of justification is not complete until we reach reflective equilibrium. Until we consider at least some main applications of the principles, we are not yet in a position to test them against many of our considered judgments and provisional fixed points.