theory, because it does not guarantee justice, and he says he wrote his book to refute it, as it will not go away until a better alternative is in place.

Rawls argues that the best basis for a society is justice, which he defines as fairness. He says that given a situation in which people have to devise a social system in which they do not know ahead of time where they will end up, they will prefer a system based on fairness to a system based on utilitarianism. As Rawls notes, increasing the average happiness is not the same as increasing justice. He uses slavery as an example, saying that it could provide for the greatest aggregate happiness but would not be a just system. Rawls writes,

Consider an extreme case: a slaveholder when confronted by his slaves attempts to justify his position to them by claiming that, first of all, given the circumstances of their society, the institution of slavery is in fact necessary to produce the greatest average happiness

Rawls says, however, that we don't need to go as far as slavery to see that an intrinsic part of the utilitarian worldview is the logic of trading away rights and freedoms for greater happiness. In the end, Rawls says, this leads to injustice and that for this reason, we need to reject utilitarianism.