 We have no reason to suppose that human behavior is so uniform in its motivation. A far more plausible hypothesis about human motives is that they vary a great deal from one person to another. Some people are never altruistic; others are just as this weak form of psychological egoism says: they are altruistic, but only when they think this will not detract from their own well-being; and then there is a third and large category filled with people who, to some degree or other, are willing to sacrifice their well-being for others. Within this category there is wide range—some are willing to make only small sacrifices, others larger sacrifices, and some extraordinarily large sacrifices. This way of thinking has the great advantage of allowing our experience of each individual to provide us with the evidence by means of which we characterize him. We should not label everyone as an egoist on the basis of some a priori theory; rather, we should assess each person’s degree of egoism and altruism on the basis of what we can discern of their motives.