Not too long ago, it was actually a very good idea to stuff yourself whenever you had food because for all you know you might be enduring drought and famine soon -- and living off your fat! For most of human history, becoming fat was perfectly rational. Very recently, we humans have created an environment in which our hard-wired behavior is no longer rational. So m-- here comes the paternalism -- why not impose a tax on refined starch, refined sugar, and fat. This would revise the incentives we have to eat one sort of food rather than another, bringing our behavior back in line with conduct that is rational. We would become healthy and wealthy, without ever incurring the expense of becoming wise! (A related idea is considered by Gary Becker here.)
Here is David's comment on this:
If we had a government run by benevolent philosopher kings, that might make sense. The problem with it in the world we live in is that although I may sometimes be a bad judge of my own welfare, sometimes even a bad judge in predictable ways--arguably the central point of behavioral economics--I have one enormous advantage over any one else when it comes to making decisions about my own welfare. Unlike almost everyone else in the world, I can be trusted to put my own welfare very high in my priorities. Once we shift the decision to someone else, however rational, we can expect him to make decisions for me in his interest rather than mine.The goal of self-control is generally self-interest. The goal of other-control is unfortunately other-interest.
My own view is that other-control is even worse, in comparison with a regime of self-control, than David makes it sound. When others control me, I have noticed, they often aren't even trying to promote their own rational self-interest (at least as we would intuitively think of it). They often are trying to make me do what is "right" (not use drugs, not use hate-speech, not carry a hand-gun, etc.).
The potential for irrationality in this sort of regime is truly immense.
One trouble with this sort of decision-making is that it does not set up any feed-back mechanism that would cause the controller to change his or her policy. If they were trying to exploit me economically then at least they could look at the bottom line and see whether they are making any money off of me. But if the decision was made just because it was "right," why, no amount of bad stuff that happens either to me or to them would prove them wrong. If I am unhappy with my drug-free life or get killed because I didn't have a gun, those are just some of the costs "we" have to pay on order to do our duty! If the war on drugs puts a third of a million young men in prison, and use of dangerous drugs is still rampant, that is a reason to -- redouble our efforts! Does this sound familiar at all?
What both rebuttals to the Darwinian argument, mine and David's, have in common is of course the idea that in the real world, other-controllers are not going to make precise re-adjustments of the incentive-structure in the direction of true rationality. So a model in which they do so, while interesting perhaps, has no implications for what we ought to do about real governments. What we should do with them is -- replace paternalistic other-control with self-control!