John Rawls uses the idea of a veil of ignorance to argue that fair distribution can be defended on rational grounds, not moral ones. He asks us to imagine a situation where we have to decide how society should be organised without knowing what position we would occupy in that society.

Under this veil of ignorance, we do not know which family we would be born into, whether we would be rich or poor, privileged or disadvantaged, or born into an upper or lower caste. Since no one knows who they would be or what would benefit them, each person would naturally think in terms of their own interests.

However, because no one knows their future position, each person would envisage the future society from the point of view of the worst-off. It would be rational to support rules that ensure reasonable opportunities to weaker sections, as one might end up being born in a disadvantaged position with few opportunities.

Rawls argues that rational persons would also ensure that policies benefit society as a whole, not just any particular section. They would seek rules that protect them if born among the worst-off, but also ensure that the better-off are not weakened, as they could be born into a privileged position.

Thus, such fairness would be the outcome of rational action, not benevolence or generosity. This provides a rational justification for acknowledging the need to help the least privileged members of society.