John Rawls, answered from the texts and cited to the page.
The veil of ignorance is a methodological device, not a metaphysical claim about human nature. It operates within the original position — a hypothetical situation designed to model the conditions under which free and equal citizens would agree on principles of justice for the basic structure of society. The core idea is this: when parties are choosing principles of justice, they must do so without knowing their place in society, their class position or social status, their distribution of natural talents and abilities, their particular conception of the good, or their distinctive psychological dispositions.1
The reason for these exclusions is straightforward — if any party knew such facts about themselves, they would be tempted to propose principles favorable to their own position, and the agreement reached would reflect bargaining advantages rather than fair terms among equals.2 The veil strips away precisely those contingent advantages that arise from cumulative social, historical, and natural tendencies, so that the principles chosen govern the basic structure from a genuinely impartial standpoint.3
Two objections arise immediately, and both deserve a direct answer. First, one might ask: if the agreement is hypothetical and nonhistorical, what binds anyone to it? The answer is that the original position is a device of representation, not a real contract.4 Its significance lies in what it models — namely, the conditions we regard, here and now, as fair for specifying terms of social cooperation among free and equal citizens.5
The agreement's force comes from the fairness of the procedure, not from a historical act of consent. Second, one might worry that the veil presupposes some metaphysically thin, unencumbered self stripped of all attachments. It does not. The parties behind the veil are not real persons emptied of their ends; they are representatives of free and equal moral persons reasoning under conditions that model impartiality.6
The veil is a modeling tool — it ensures that no one is advantaged or disadvantaged by natural contingencies or social chance in the adoption of principles.7 There is also a further consequence worth noting. Because the veil excludes any prior and independent notion of desert — perfectionist or otherwise — citizens come to deserve what they do through their actual decisions and efforts within an ongoing background system of cooperation with publicly announced rules.8
Desert, on this view, is derivative from the principles the parties agree to, not a prior standard that could override those principles. The name "justice as fairness" captures the underlying conjecture precisely: the fairness of the circumstances under which agreement is reached transfers to the principles agreed to.9
they do not know their place in society, their class position, or social status, nor do they know their fortune in the distribution of natural talents and abilities. It is assumed also that they do not know their conception of the good, that is, their particular final ends; nor finally, their own distinctive psychological dispositions and propensities.16 Kantian Constructivism in Moral Theory, p. 325
Excluding this information is required if no one is to be advantaged or disadvantaged by natural contingencies or social chance in the adoption of principles. Otherwise the parties would have disparate bargaining advantages that would affect the agreement reached.16 Kantian Constructivism in Moral Theory, p. 325
the conditions for a fair agreement on the principles of political justice between free and equal persons must eliminate the bargaining advantages that inevitably arise within the background institutions of any society from cumulative social, historical, and natural tendencies.Political Liberalism, pp. 58–59
it is clear that the original position is to be seen as a device of representation and hence any agreement reached by the parties must be regarded as both hypothetical and nonhistorical.Political Liberalism, pp. 59–60
it models what we regard—here and now—as fair conditions under which the representatives of free and equal citizens are to specify the terms of social cooperation in the case of the basic structure of society.Political Liberalism, pp. 59–60
the parties are symmetrically situated is required if they are to be seen as representatives of free and equal citizens who are to reach an agreement under conditions that are fair.Political Liberalism, pp. 59–60
these and other limitations on information are necessary to establish fairness between the parties as free and equal moral persons and, therefore, to guarantee that it is as such persons that they agree to society's basic principles of justice.16 Kantian Constructivism in Moral Theory, p. 325
citizens come to deserve this or that by their actual decisions and efforts within an ongoing background system of cooperation with publicly announced rules that support legitimate expectations and acquired claims.16 Kantian Constructivism in Moral Theory, pp. 353–354
we conjecture that the fairness of the circumstances under which agreement is reached transfers to the principles of justice agreed to; since the original position situates free and equal moral persons fairly with respect to one another, any conception of justice they adopt is likewise fair.16 Kantian Constructivism in Moral Theory, p. 325