Ezra writes:

I think Brooks’s point is that the power of non-policy factors should inspire modesty among believers in government intervention. And he’s right about that. But it goes in reverse, too: The complexity of these outcomes should inspire modesty about the relevance of broad philosophical insights rather than well-designed tests of specific interventions. Brooks’s column doesn’t favor the conservative’s principled belief in less government so much as the technocrat’s commitment to voluminous evidence and careful studies.

This glosses over a deeper problem, namely what ought to count as useful evidence and what it means to conduct a careful study. The experimental sciences have a profound advantage over the non-experimental sciences. And though Vernon Smith and Alvin Roth and Esther Duflo, among many others, have made impressive strides in introducing experimental techniques into economics, the truth is that there is very little in the realm of public policy than we can conclusively know, the way we know about so-called physical laws.

Very recently, Jim Manzi wrote a short post on Esther Duflo that directs readers to a longer manifesto he wrote for The Atlantic on the implications of this deep uncertainty:

Much of the work that we now think of as economics, political science and other social sciences will likely be displaced by some hybrid of biology, experimental economics, psychology and other fields that can evaluate hypotheses for the quantified prediction of human behavior through structured falsification tests (or, sometimes, true “natural experiments” in which non-intentional random assignment has occurred). As I’ve gone into in a recent post on possible interpretations of a specific clinical trial in Ghana, the big constraint on the practical utility of this science will likely be the problem of generalization from experimental results to forward predictions. Even in its current embryonic form, experimental economics already suffers from excessive rhetorical generalization from what some specific group of college sophomores did with $30 to fairly grand statements about human nature. But, as with business experimentation, where applicable, this new approach will dominate what we now think of as classical economics.

There is a long way to go between the kind of evidence that Ezra considers useful and the evidence that, say, the manufacturers of airplane wings are obligated to gather before they commit to a particular design. When do we have enough evidence? Who decides on what counts as evidence, and is cognitive closure at work among those decide that they are the ones who should decide?

A friend of mine noted that when T. Boone Pickens predicted the coming of Peak Oil in the 1970s, he lost that bet; and so the Peak Oilers tended to scatter into other sectors of the economy, leaving behind a class of people in the oil and gas industry who are strongly inclined to reject the Peak Oil view, and to inculcate those views in younger cohorts — whether or not the underlying evidence has changed, peer pressure and hidden biases can have a powerful impact on how we think about the world.

The principled belief in less government is precisely about the limits of what we can reliably and usefully know about human behavior. It is about preserving room for diversity and experimentation by maintaining flexible frameworks for building new institutions, new business models, and new ways of life. Many conservatives, incidentally, are very antsy about this kind of experimentation, which is why conservatives often favor more rather than less government.

But the case for less government, and the case for incremental rather than radical change, is directly related to the fact that social planning is really, really, really, by which I mean all but impossibly, hard.

Matt has written a different take on David Brooks’s latest column, and I’m very sympathetic to it:

I think the real lesson here is that Sweden and the US (especially the parts of the US where Swedes tended to settle) actually don’t have entirely different political systems. North Korea and South Korea have entirely different political systems. Sweden and Zimbabwe have entirely different political systems. The United States and Uzbekistan have entirely different political systems. The United States and Sweden are both stable democracies with market economies, substantial welfare states, and relatively low levels of public corruption. I think the real lesson of Brooks’ story is that the policy differences between stable market/welfare democracies are not that large and especially that controversies about tax levels are overblown in terms of their consequences.

As I read it, Matt and Ezra are coming at this question from very different angles. According to Matt, what matters is the broad outline of the political systems. Ezra is suggesting that we can derive conclusive answers about very fine-grained questions. I see a lot of daylight between these positions, and I’m inclined to embrace Matt’s take. The truth is that the U.S. has an intrusive and interventionist a government as Sweden. The main difference is that we rely more heavily on inefficient populist credit expansion than on more transparent direct transfers. I tend to think that we’d be better off with a lot less populist credit expansion and perhaps slightly more in the way of transparent direct transfers. But my commitment to humility dictates that I be open on this question!