One of my favorite writers on policy is Jim Manzi. He has a book coming out called "Uncontrolled" in which, I take it, he explores the limitations of social science (at least as currently practiced) and the value of randomized controlled trials.
In commenting on the book, Arnold Kling writes something that I think goes to the heart of what makes many people - including me - conservatives. Kling begins by noting that society, at any given time, includes both "embedded" wisdom and "embedded error." He continues:
The application of social science to public policy is an attempt to use conscious knowledge to replace embedded error. What I call Hayekian conservatism is the view that social scientists know so little that these attempts are more likely to undermine embedded wisdom than to correct embedded error. Therefore, policy ought to be cautious. .....
Hayek would argue that there is embedded wisdom in society that is beyond the understanding of social scientists. Call these the "unknown knowns," if you will. That is, social scientists are not aware of how habits and institutions work, but these habits and institutions have, through evolution, accumulated tacit knowledge. As social scientists, we can make some guesses about how property rights, the rule of law, trust, and trade contribute to higher per capita GDP. However, we are not able to explicitly "fix" underdeveloped countries. Richer countries are richer in the unknown knowns.Extremely well put and much more important, I think, in the Age of Obama. As I argued here, he is strongly in the tradition of "top-down" Progressivism. He favors comprehensive, uniform, centrally determined policies.
(H/T: Russ Roberts)