It may be that this difference in the conception of ideal justification follows from an unannounced paradigm shift. While Rawls would seem to prefer an efficient justification capable of yielding a single judgment for all time without, ideally, backwards movement, Stout would set out from an opposed position whereon a dialectical, circular movement would issue in positions to which we incessantly come back. Were we to distill this distinction to its simplest form, we could hold that Rawls privileges a closed(-ended) ideal justification over Stout’s open-ended ideal justification when the time comes to justify the basic structure of society.
One consideration which Rawls puts forward in favor of his more closed(-ended) approach is the notion of stability. More precisely, the thinker holds that the basic structure of society must demonstrate stability in order to apply a set of just standards consistently and to secure each person’s consent to the basic structure of society and its institutions. In light of these conditions, the surest way whereby we might arrive at a stable situation would follow from an ideal justification always issuing in one and the same conception of justice. Indeed, this aligns with Rawls’ appeal to pure procedural justice as a manner of fixing results as invariably just. Unconstrained justification undermines an end-state capable of instantiating the conception thereby arrived at.
Confronted with charges of instability, we may wonder how Stout would respond thereto. The clearest way forward would lie in denying said charges and turning Rawls’ contention on its head. In other words, Stout could conceivably show in what way unconstrained justification better fulfills the conditions of stability. In truth, the person’s freedom to express her real reasons for a particular conception of justice may increase the likelihood that the person consents to the basic structure of society and its institutions. For that person will have made, in one way or another, a contribution to the shape of the basic structure and its institutions. Moreover, nothing hinders the consistent application of a set of just standards within a given time and place, i.e. within the limits of a concrete location and time period. There is no reason prima facie to suppose that mutable standards will necessarily change from one day to the next and prevent a consistent, durable application.
Accordingly, Stout would arrive at a position whereon the two conditions are, at least partially, fulfilled, and he can consequently turn aside Rawls’ charges of instability. Yet he could push his refutation further in maintaining that Rawls’ constrained justification falls prey to its own variety of instability in two distinct fashions. On one hand and somewhat exaggeratedly, a conception of justice which does not evolve in time with its social environment and resulting changes in the conditions of justification of conceptions of justice will inevitably bring on conflict between a.) the application and the institutions of that conception of justice and b.) the cognitive context and conceptual economy framing the justification of a given conception of justice. In short, the conception of justice underlying society would not evolve in time with that society’s assumptions about justice and institutions. On the other hand, Stout could contend that Rawls’ constraints on individual expression in ideal justification might frustrate citizens to the point that they feel it necessary to overturn the basic structure with its underlying conception of justice and its associated institutions. In sum, constrained ideal justification and the resultant basic structure prove too rigid for adaptation and continued survival.
Wherefore the most striking difference between these authors: constraints, or lack thereof, on contingent factors in ideal justification.