I suppose I’ll have to read Manzi’s book to find out how existing practices constitute “(metaphorical) judgments about packages of policy decisions;” I’m inclined to regard them as mostly mere resultants-of-forces, with little claim to deference. (Thinking that existing arrangements somehow embody tacit knowledge is a different matter from thinking that big changes are likely to have unexpected consequences, mostly bad, though both are arguments for caution about grand projects.)
I’m also less unimpressed than Manzi is with how much non-obvious stuff about humans living together the social sciences have already taught us. That supply and demand will, without regulation, come into equilibrium at some price was a dazzling and radical social-scientific claim when Adam Smith and his friends suggested it. So too for Ricardo’s analysis of comparative advantage, which, while it doesn’t fully support the free-trade religion that has grown up around it, at least creates a reasonable presumption that trade is welfare-increasing.
The superiority of reward to punishment in changing behavior; the importance of cognitive-dissonance and mean-regression effects in (mis)shaping individual and social judgments; the intractable problem of public-goods contributions; the importance of social capital; the problems created by asymmetric information and the signaling processes it supports; the crucial importance of focal points; the distinction between positive-feedback and negative-feedback processes; the distinction between zero-sum and variable-sum games; the pervasiveness of imperfect rationality in the treatment of risk and of time-value, and the consequent possibility that people will, indeed, damage themselves voluntarily: none of these was obvious when proposed, and all of them are now, I claim, sufficiently well-established to allow us to make policy choices based on them, with some confidence about likely results. (So, for that matter, is the Keynesian analysis of insufficient demand and what to do about it.)
But, if I read Manzi’s response correctly, my original comment allowed a merely verbal disagreement to exaggerate the extent of the underlying substantive disagreement. If indeed Manzi can offer some systematic analysis of how to look at existing institutions, figure out which ones might profitably be changed, try out a range of plausible changes, gather careful evidence about the results of those changes, and modify further in light of those results, then Manzi proposes what I would call a “scientific” approach to making public policy.
If all Manzi means when he disses “social science” is that you shouldn’t just read some random paper in an economics or social-psych journal and propose some insanely risky venture such as privatizing Social Security or voucherizing public education or wiping out labor unions based on that paper, then I’m happy to stand shoulder-to-shoulder with him against irresponsible radicalism and for cautious and evidence-sensitive approaches to bringing about social improvement.