Original position
From Internet: Knowledge and Community
In the context in which Rawls applies it, the concept of an original position of equality refers to a sense of balance in society amongst its citizens as far as social or class standings are concerned as the basis from which justice as fairness is reasoned. In the original position, people are assumed to be behind a veil of ignorance, so that no person is aware of anything about themselves or their place in society; theoretically, this makes everyone equal to begin with. If no one is aware of their own situation, then they at least all have that in common.
Due to the fact that everyone is equal in ignorance toward themselves, regardless of whether they are rich or poor, or whatever abilities or attributes they may or may not possess, fair is fair. This concept is hypothetical precisely because, in reality each person is aware that they are born into a particular status and situation which can influence them to feel entitled to succeed based on that. Essentially, original position presupposes that people would cooperate efficiently if they all believed things were fair in relation to one another from the get go.
