Brad DeLong posts what he says is his all-time favorite Paul Krugman essay.
In it, Krugman exposes former House Majority Leader Dick Armey as a liar and a fool. You probably already knew both things to be true about Armey, but go read the essay anyway.
Krugman's topic is actually the effect and the policy implications of wealth inequality. What I found most helpful and compelling in the essay is his parable of two different simple societies and the different policies that each should enact to deal with inequality in accord with prudence and justice.
In Ecclesiastes 9:11, the Teacher writes:
The race is not to the swift or the battle to the strong, nor does food come to the wise or wealth to the brilliant or favor to the learned; but time and chance happen to them all.
Any economic theory or public policy that fails to account for this is not merely false and foolish, it is inhuman.