 SN is more demanding than  I.[9] I requires consistency for each pair of alternatives separately, as we go from one profile in the domain to the next. SN also requires this, but in addition it requires consistency as we go from one pair to the next, whether that is within a single profile or among several different ones. This is how SN keeps non-welfare features from making any difference: by compelling the social welfare function to treat any two pairs of alternatives the same way, if the pattern of individual preference is the same for both.