Say I bought a fancy pair of shoes for my son. In light of the one-tribe calculus of interests, I should probably give these shoes to someone who doesn’t have any. I do research and find a child in a poor part of Chicago who needs shoes to walk to school every day. So, I take them off my son (replacing them with Walmart tennis shoes) and head off to the impoverished Westside. On the way, I see a newspaper story about five children who are malnourished in Cambodia. Now I can’t give the shoeless Chicago child the shoes, because I should sell the shoes for money and use the money to get food for the five malnourished kids. On my way to sell the shoes, I remember that my son has an important job interview for a clean-water nonprofit organization and if he gets the job, he’ll be able to help save whole villages from contaminated water. But he won’t get the job if he shows up in Walmart tennis shoes. As I head back home, it dawns on me that for many people in the developing world, Walmart tennis shoes are truly luxurious when compared with burlap sack shoes, and since needs always trump luxuries I’ll need to sell the tennis shoes too; and on, and on, and on.
Stephen Asma from the NYT.