"The difference principle tries to establish objective grounds for interpersonal comparisons in two ways. First of all, as long as we can identify the least advantaged representative man, only ordinal judgments of wellbeing are required from then on. We know from what position the social system is to be judged. It does not matter how much worse off this representative individual is than the others. The further difficulties of cardinal measurement do not arise since no other interpersonal comparisons are necessary. The difference principle, then, asks less of our judgments of welfare. We never have to calculate a sum of advantages involving a cardinal measure. While qualitative interpersonal comparisons are made in finding the bottom position, for the rest the ordinal judgments of one representative man suffice. Second, the difference principle introduces a simplification for the basis of interpersonal comparisons. These comparisons are made in terms of expectations of primary social goods. In fact, I define these expectations simply as the index of these goods which a representative individual can look forward to. One man’s expectations are greater than another’s if this index for some one in his position is greater. Now primary goods, as I have already remarked, are things which it is supposed a rational man wants whatever else he wants."