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The best refutation of this argument that I've seen in a long time is contained in a new book, "The Persistence of Poverty," by a friend of mine, Charles "Buddy" Karelis, a professor at George Washington University. Karelis isn't an economist or social welfare expert but a philosopher by profession with wide-ranging curiosity, a dry wit and a weakness for unconventional wisdom. And after doing lots of reading and giving it extensive thought, Karelis concluded that the reason some people are perpetually poor is that they don't have enough money.

Let me say that this isn't as self-evident, or tautological, a truth as it might appear. Rather, the argument goes something like this:

The reason the poor are poor is that they are more likely to not finish school, not work, not save, and get hooked on drugs and alcohol and run afoul of the law. Liberals tend to blame it on history (slavery) or lack of opportunity (poor schools, discrimination), while conservatives blame government (welfare) and personal failings (lack of discipline), but both sides agree that these behaviors are so contrary to self-interest that they must be irrational.

After all, the reason we study, work, save and generally behave ourselves is that these behaviors allow us to earn more money, and more money will improve our lives. And, by logic, that must be particularly true of the poor, for whom each extra dollar to be earned or saved for a rainy day is surely more valuable than it is for, say, Bill Gates.

In economics, this insight -- that the fifth ice cream sundae is less valuable than the first one -- is enshrined in the law of diminishing marginal utility.

But what if this iron law of economics is wrong? What if it doesn't apply at every point along the income scale? If you and everyone around you are desperately poor, maybe it's perfectly rational to think that an extra dollar or two won't make much of a difference in reducing your misery. Or that you won't be able to "study" your way out of the ghetto. Or that if you find a $100 bill on the street, maybe it's logical to blow it on one great night on the town rather than portion it out a dollar a day for 100 days.

On the other hand, maybe the point at which people are most willing to work hard, save and play by the rules isn't when they are very poor, or very rich, but in the neighborhoods on either side of the point you might call economic sufficiency -- a motivational sweet spot that, in statistical terms, might be defined as between 50 percent ($24,000) and 200 percent ($96,000) of median household income. And if that is so, then maybe the best way to break the cycle of poverty is to raise the hopes and expectations of the poor by putting them closer to the goal line.

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