The veil of ignorance is a very important part of Rawls’ argument in A Theory of Justice. It allows us to evaluate possible actions without prejudice. This makes it possible for us to do a better job of understanding whether a potential action would be just.
Rawls says that we must use the veil of ignorance when trying to decide if a certain way of ordering society or changes to our society are just. To use the veil of ignorance, a person must think about society without knowing what place they hold in that society. For example, if we are going to introduce more free market reforms to ensure that people have to compete to prosper in our society, we have to think about this without knowing whether we are likely to be well-placed in that competition. It is easy to advocate for more competition if you have been born to a middle class, educated family. But what if you do not know whether you are going to be placed in a lower class family where no one is educated and you have no way to compete effectively? Your perspective on the justice of this course of action might be different.
This is what the veil of ignorance does for us. It allows us to think about changes to our society in a more objective way. If we effectively use the veil of ignorance, we think about how changes will affect everyone in our society, not just those who are like us.