A well-founded contract must fulfil the full condition of publicity: its full justification must be able to be effectively accepted by members of a well-ordered society. The hypothetical agreement itself provides only what Rawls (1996, 386) calls a “pro tanto” or “as much as possible” justification for the principles of justice. “Full justification” is only achieved if “people support and become liberal justice for the particular (and often contradictory) reasons that are implicit in the full reasonable doctrines they retain” (Freeman 2007b, 19). Thus understood, rawls` concern for the stability of justice as equity, which motivated the transition to political liberalism, is itself a matter of justification (Weithman, 2010). Only if the principles of justice are stable in this way are they fully justified. However, Rawls` concern for stability and publicity is not unique and is shared by all contemporary contractual theorites. It is significant that even theorists like Buchanan (2000, 26-27), Gauthier (1986, 348) and Binmore (2005, 5-7) – who are so different from Rawls in other respects – share his concern for stability. We could distinguish between negotiations and aggregation solutions. Instead of looking for a result that, as the Kalai-Smorodinsky solution pretty much does, divides the difference between the different claims, we could try to bring the different rankings together into a general social choice. Arrow`s sentence and the problems associated with the rules of social choice cast doubt on any claim that a certain type of aggregation is merely rational: all have their flaws (Gaus 2008, chap. 5). Harsanyi (1977, Chapter 1 and 2; 1982) developed a contract theory similar to Rawls`s. It creates a veil of ignorance in which people do not know their identities under the contract and assumes that rational contractors will assume that they are just as likely to be a particular person.
In addition, it argues that contractors can agree on people-to-people supply comparisons and will therefore choose a contract that will aggregate the supplier in the highest average (see also Muller 2003, chap. 26). It depends, of course, on the assumption that there is an undisputed metric that allows us to aggregate the usefulness functions of the parties. Binmore (2005) follows Harsanyi and Amartya Sen (2009, chap. 13) on the grounds that interpersonal comparisons can be made for aggregation purposes, at least in part. However, one of the problems with this approach is that interpersonal comparisons, if incomplete, will not be able to achieve a complete social order.