A lot of people don't seem to get John Rawls' political philosophy, with its concepts of the "Original Position" and the "Veil of Ignorance," so here's an analogy that I think might help people understand it better.
Imagine that the Eastern religions were partially right, and when you die, you'll be reincarnated. Not as an animal, and not as some kind of higher spiritual being on a higher plane, but as another human here on Earth. But the Eastern religions were also partially wrong, in the sense that reincarnation won't be a reward or punishment - you won't come back as a rich and healthy person if you did good deeds, or as a poor and sickly person if you committed evil acts, it's just completely random.
The ONLY real karma, the only way in which your present life can affect your future lives, is through the changes you make to the world as a whole. So, given that knowledge, it would be in your interest to make decisions that make the world better for everyone. You wouldn't want to just benefit Americans at the expense of everyone else, because you have a much higher chance of being born as a non-American in your next life, since the U.S. only contains 4% of the world's population. You wouldn't want a system where the rich get infinitely richer and the poor get infinitely poorer, because you have a much higher chance of being born as a poor person in your next life, simply due to the fact that a lot more poor people exist. (Of course, you also might not want a system that was perfectly equal if it meant that the overall median quality of life was lower, or if any attempts to achieve that goal necessitated a violent and chaotic revolution that risked making everything worse for the majority of people, which is why Rawls was a liberal and not a radical leftist.)
Now, this is just an analogy, and I'm not endorsing it as an actual belief system. As far as I know, Rawls didn't actually believe in reincarnation, and he certainly didn't mention it in his writing. But his concept of the "Veil of Ignorance" is based around a similar idea: the notion that, in order to have a truly just society, we should construct our social, cultural, political, and economic system as though we were designing it from a hypothetical "Original Position" outside of that system, where we would have no idea who we would be within it.