The value criterion is...consistency with the original position.
Here are some of the best justifications for a Rawls framework.
Core to any conception of justice is that we prevent arbitrary rights allocation. RAWLS:
John Rawls. Professor at Harvard: A Theory of Justice, 1971
Existing societies are of course seldom well-ordered in this sense, for what is just and unjust is usually in dispute. Men [ People] disagree about which principles should define the basic terms of their association. Yet we may still say, despite this disagreement, that they each have a conception of justice. That is, they understand the need for, and they are prepared to affirm, a characteristic set of principles for assigning basic rights and duties and for determining what they take to be the proper distribution of the benefits and burdens of social cooperation. Thus it seems natural to think of the concept of justice as distinct from the various conceptions of justice and as being specified by the role which these different sets of principle, these different conceptions, have in common. Those who hold different conceptions of justice can, then, still agree that institutions are just when no arbitrary distinctions are made between persons in the assigning of basic rights and duties and when the rules determine a proper balance between competing claims to the advantages of social life. Men can agree to this description of just institutions since the notions of an arbitrary distinction and of a proper balance, which are included in the concept of justice, are left open for each to interpret according to the principles of justice that he accepts. these principles single out which similarities and differences among persons are relevant in determining rights and duties and they specify which division of advantages is appropriate. clearly this distinction between the concept and the various conceptions of justice settles no important questions. It simply helps to identity the role of the principles of social justice.
People do not choose the conditions available to them. Opportunities influence prospects. Such benefits are arbitrarily acquired and should not enter justice. This necessitates the original position. RAWLS (2):
One should not be misled, then, by the somewhat unusual conditions which characterize the original position. The idea here is simply to make vivid to ourselves the restrictions that it seems reasonable to impose on arguments for principles of justice, and therefore on these principles themselves. Thus It seems reasonable and generally acceptable that no one should be advantaged or disadvantaged by natural fortune or social circumstances in the choice of principles. It also seems widely agreed that It should be impossible to tailor principles to the circumstances of one’s own case. We should insure Further that particular inclinations and aspirations, and persons’ conceptions of their good do not affect the principles adopted. The aim is to rule out those principles that it would be rational to propose for acceptance, however little the chance of success, only if one knew certain things that are irrelevant [to] from the standpoint of justice. For example, If a man knew that he was wealthy, [they would not] might ﬁnd it rational to advance the principle that various taxes for welfare measures be counted unjust; if he knew that he was poor, [they] would most likely propose the contrary principle. To represent the desired restrictions one imagines a situation in which everyone is deprived of this sort of information. One excludes the knowledge of those contingencies that set men at odds and allow them to be guided by their prejudice.
The standard is consistency with the original position. Goodness or badness is based on conforming the will to this principle since knowledge of how things will empirically fare is precluded from actors behind the veil – we could accord a principle to help poor people, but if I got crushed by a boulder before donating money I wouldn’t be responsible for failure even though I acted as an actor in the original position would endorse.
[This framework originally and generously contributed by Torrey Pines VB.]