In support of some market interventions endorsed by the populists who today dominate the GOP, Glenn Hubbard counsels traditional conservatives to agree “with populist conservatives that markets don’t always work perfectly” (“The Economic Populists Have a Point,” op-ed, July 19).

I challenge Prof. Hubbard to identify a single serious conservative or libertarian scholar whose case for free markets rests on the belief that markets “always work perfectly.” Such a creature is imaginary. Not Adam Smith; not F.A. Hayek; not Milton Friedman; not Vernon Smith; not Deirdre McCloskey; not your frequent contributor, Phil Gramm; not anyone of any stature who supports free markets has ever grounded that support on the assumption of perfect markets.

The case for free markets—and against nearly all interventions desired by today’s populists—is that markets are less imperfect than governments. Most market imperfections are profit opportunities that in time attract entrepreneurs to experiment with ways to improve matters. Some experiments work, many fail. Unlike government officials, private market actors spend their own money and have no power to coerce.

Markets identify and correct mistakes more quickly than do governments, are less prone to be captured by interest groups and are more driven to strike trade-offs in mutually advantageous ways rather than in ways that compel some individuals to pay for the gains of others.