Mmm, tasty paragraph

Brad DeLong sums up the challenge of liberal economic policy.

Even a small amount of belief in diminishing marginal utility of wealth leads to the conclusion that the government ought to put its thumb on the scale on the side of a more middle-class and a less Second-Gilded-Age economy and income distribution. How the government should do this, however, is an extremely hard problem--a problem that it is even hard to think about because we lack an adequate theory of market failure.