Imagine that you have set for yourself the task of developing a totally new social contract for today's society. How could you do so fairly? Although you could never actually eliminate all of your personal biases and prejudices, you would need to take steps at least to minimize them. Rawls suggests that you imagine yourself in an original position behind a veil of ignorance . Behind this veil, you know nothing of yourself and your natural abilities, or your position in society. You know nothing of your sex, race, nationality, or individual tastes. Behind such a veil of ignorance all individuals are simply specified as rational, free, and morally equal beings. You do know that in the "real world", however, there will be a wide variety in the natural distribution of natural assets and abilities, and that there will be differences of sex, race, and culture that will distinguish groups of people from each other.
In this original position , behind the veil of ignorance, what will the rational choice be for fundamental principles of society? The only safe principles will be fair principles, for you do not know whether you would suffer or benefit from the structure of any biased institutions. Indeed the safest principles will provide for the highest minimum standards of justice in the projected society.
To use a more mundane illustration, imagine that you had the task of determining how to divide a cake fairly among a group of individuals. What rule or method should govern the cutting? A simple one would be to let the person who does the cutting receive the last piece. This would lead that person to cut all pieces as equally as possible in order to receive the best remaining share.