Although broader ethnic or religious loyalties sometimes supervene, people all over the world attach special importance to the fate of their compatriots. How to measure the preferential factor is an intriguing question: perhaps we could measure the front–page space devoted to domestic and international matters respectively, or the extent of a foreign as opposed to a domestic disaster needed to cross the threshold of attention, or compare foreign–aid budgets with domestic welfare and social service expenditures. Or perhaps we could measure generally accepted “them–us” kill ratios in warfare. Some measures might yield a very high factor: possibly compatriots are given a thousand times more weight, perhaps more, in some respects. But of course, even if compatriots were (implicitly) judged to be worth only (!) twice as much as others, we should still want to know why. Sometimes psychological reasons are given: it is argued, for example, that Rousseau was right to claim that human attachments weaken as they extend, that they must stop somewhere if they are to retain any motivating force and remain reliable. We should, however, still want to know if we are justified in doing what we feel inclined to do. Moreover, Rousseau's spatial model does not actually fit the facts at all well.