Peter Singer offered this challenge in the Oct/Nov issue of Free Inquiry (not available on-line):

Imagine that you are walking through a park past a shallow ornamental pond, and you notice that a child has fallen into that pond and seems to be in danger of drowning. You look around for the parents or the babysitter, but there is no one in sight. What should you do? Obviously, you should rush into the pond and save the life of the child. But wait a minute--you are wearing your most expensive shoes, and you don't have time to kick them off. They will be ruined if you go into the pond with them on. Do your shoes make a difference in your decision? Everyone agrees that they don't. You can't let a pair of shoes mean more than a child's life. So how about giving just the cost of an expensive pair of shoes to an organization that is saving lives in developing countries? I don't think it is any different than saving the child in the shallow pond. Yes, it is different psychologically but not morally. Distance doesn't make someone's life less valuable.

Singer's implicit assumption is that your dollars are fungible. When you spend a dollar on a luxury, it is dollar that you could have spent to save the life of a dying child. In other words, dollars don't come pre-categorized such that some dollars can only be spent on luxuries. You cannot escape this logic. Therefore, If Jesus (or whatever God you might believe in) were watching, you closely, and you knew it, you couldn't possibly pay $300 for a pair of shoes when perfectly adequate $100 shoes were also available and when you knew (as you always do know) that the other $200 could be used to save the lives of innocent children. I get frustrated with those who think that the commandment "Do not kill" is not being violated by those who spend excessive money on fancy clothes, cars or houses (or buy any luxury) in the same world where children are dying every day and those deaths are preventable. That said, I don't think that "Do not kill" is a workable rule. It rings nicely to simple ears because it is phrased uncategorically, but we really need a new rule that recognizes that we are not exactly a nation of murderers when we buy a steady stream of unnecessary luxuries (especially at Christmas time), but it's something like that when we completely unhinge our consciences from our wallets, which so many of us in sanctimonious American do almost every day. I don't really know how to articulate such a rule, but I do want to take this moment to recognize this undeniable fact as part of my "Life is Real" campaign: Every day, most of us in American choose to buy things with dollars that could be used for saving the lives of real children. That's the way things are down here on planet Earth, and going around claiming that "Do not kill" only means don't shoot or stab innocent people doesn't change things one bit.