Veil of ignorance
The veil of ignorance and the original position are concepts introduced by John Harsanyi and later appropriated by John Rawls in A Theory of Justice. It is a method of determining the morality of a certain issue (e.g., slavery) based upon the following thought experiment: parties to the original position know nothing about their particular abilities, tastes, and position within the social order of society.
The veil of ignorance blocks off this knowledge, such that one does not know what burdens and benefits of social cooperation might fall to him/her once the veil is lifted. With this knowledge blocked, parties to the original position must decide on principles for the distribution of rights, positions and resources in their society. As Rawls put it, "...no one knows his place in society, his class position or social status; nor does he know his fortune in the distribution of natural assets and abilities, his intelligence and strength, and the like". The idea then, is to render moot those personal considerations that are morally irrelevant to the justice or injustice of principles meant to allocate the benefits of social cooperation.
For example, in the imaginary society, one might or might not be intelligent, rich, or born into a preferred class. Since one may occupy any position in the society once the veil is lifted, the device forces the parties to consider society from the perspective of all members, including the worst-off and best-off members.
An application of the veil of ignorance towards a recognition of the worst-off members of society is captured in Mahatma Gandhi's Talisman, given in 1948.
"I will give you a talisman. Whenever you are in doubt, or when the self becomes too much with you, apply the following test. Recall the face of the poorest and the weakest man whom you may have seen, and ask yourself, if the step you contemplate is going to be of any use to him. Will he gain anything by it? Will it restore him to a control over his own life and destiny? In other words, will it lead to swaraj [freedom] for the hungry and spiritually starving millions? Then you will find your doubts and your self melt away."
The veil of ignorance is part of the long tradition of thinking in terms of a social contract. The writings of Immanuel Kant, Thomas Hobbes, John Locke, Jean Jacques Rousseau, and Thomas Jefferson offer examples of this tradition.
See also 
- Veil of Ignorance entry by Samuel Freeman in the Stanford Encyclopedia of Philosophy, 2008-20-12
- Legal Theory Lexicon: The Veil of Ignorance entry by Lawrence B. Solum in the Legal Theory Blog, 2011-11-14
- J. C. Harsanyi, Cardinal utility in welfare economics and in the theory of risk-taking, J. Polit. Economy 61 (1953), pp. 434–435.
- J. C. Harsanyi, Cardinal welfare, individualistic ethics, and interpersonal comparison of utility, J. Polit. Economy 63 (1955), pp. 309–321.
- John Rawls, A Theory of Justice, Cambridge, Massachusetts: Belknap Press, 1971. ISBN 0-674-00078-1
- John Rawls, Justice as Fairness: A Restatement, Cambridge, Massachusetts: Belknap Press, 2001.
- Rawls, John (1999). A Theory of Justice. Harvard University Press. p. 118. ISBN 0-674-00078-1.