Drawing from astrophysics, economics, and philosophy, Kevin Williamson gives a pretty good consolidation of the conservative’s starting point, with this:

The epistemic horizon [the limits beyond which we cannot see] is not very broad. We do not, in fact, know what the results of various kinds of economic policies or social policies will be, and there isn’t any evidence that can tell us with any degree of certainty. The housing projects that mar our cities weren’t supposed to turn out like that; neither was the federal push to encourage home-ownership or to encourage the substitution of carbohydrates for fats and proteins in our diets. A truly rational policy of the sort that [rationalist Neil deGrasse] Tyson imagines must take into account not only how little we know about the future but how little we can know about the future, even if we consult the smartest, saintliest, and most disinterested experts among us.

That is part of the case for limited government and free markets. Government can do some things, such as guard borders (though ours chooses not to) and fight off foreign invaders. There are things that it cannot do, even in principle, such as impose a “rational” order on the nation’s energy markets, deciding that x share of our electricity supply shall come from solar, y share from wind, z share from natural gas, all calculated to economic and environmental ideals. That is simply beyond its ken, even if all the best people — including Tyson, from time to time — pretend that it is otherwise. Free markets go about solving social problems in the opposite way: Dozens, or thousands, or millions, or even billions of people, firms, organizations, investors, and business managers trying dozens or thousands of approaches to solving social problems.

The message to progressives is: You can’t do that.  Not because we won’t let you, but because it can’t be done.  At this point in time, that’s the truth of the science.  Deal with it.

The best we can do is draw some areas on the map with the warning that “here there be dragons.”  Sailing along, we hear a rumbling off in the distance, and although we can’t state with certainty from our examinations and calculations that the noise is a cliff-face waterfall, we conclude that it would best to accept some delay to paradise and try to go around.  Perhaps we’ll avoid the danger, perhaps we’ll only get a better view of it, or perhaps we’ll never know if we made the right or wrong decision.

In short, we need to set some principles and be guided mainly by our assessment of incentives.  Maybe the most dramatically objectionable aspect of progressivism or rationalism is its denial that, historically speaking, we’re doing pretty well.  That being the case, the rational move is not to undermine what we’ve gained as a species by imagining that we’ve got the whole thing figured out well enough to discard our traditions in a potentially cataclysmic lunge for perfection.