I'm not sure I've been called an "unprincipled courtier" before. But really, I can't think of any better context in which to have that happen than (1) by the thoughtful Robin Hanson; (2) along with Matt Yglesias; and (3) in the midst of a highly abstract debate over utilitarianism and the optimal taxation of height. The system works!
This goes back a lot of posts (see here and here for the important ones), so let me see if I can summarize this in a fair way. There are two big questions here. The first is: Do you have to justify a progressive income tax on utilitarian grounds? The second is: If some particular element of the progressive income tax conflicts with a deeply held moral intuition, should you abandon the intuition or the tax?
I'm not a moral philosopher or an economist, so I'm not going to comment on the propriety of economists getting mired in moral philosophy or vice versa. But since blogging is the apparently the business of offering under-qualified opinions, I'll try to comment on just about everything else:
1. The answer to the first question -- do you have to justify the progressive income tax on utilitarian grounds? -- strikes me as an obvious "No." But it's not clear to me what counting up people who do and do not support progressive income taxation for utilitarian reasons is supposed to prove. I'm sure long lists can be produced on both sides of the battlefield. I don't think anyone in the debate holds the position that the best argument is the most popular.
2. I like John Rawls and think he offers good justifications for progressive taxation. But I agree with Hanson that it isn't obvious whether Rawls would reject a tax on height. (I asked after this in my second post on the subject.) Specifically, it isn't clear to me that such a tax violates the greatest equal liberty principle or the difference principle. As for the principle of fair equality of opportunity -- well, I dunno. I am regretting the moment in college where my friends went off and wrote their theses about Rawls and I wrote mine about some silly question that kind of had something to do with Jeremy Waldron.
3. Either way, what is obvious is that Rawls anticipates situations like the height tax -- that is, situations in which our particular moral intuitions conflict with pre-existing general principles. As I understand it, that's the whole point of reflective equilibrium: we shimmy back and forth between the general moral principle and the particular moral conundrum until there is no more shimmying to be done.
4. So, assuming that (i) Rawls' general principles wouldn't be able to reject a height tax and (ii) a height tax offends my moral intuitions, how should I shimmy closer to reflective equilibrium? As I see it there are three options here (and I think Mankiw basically lists them all in his paper): (a) abandon the general principle; (b) modify the general principle until it fits snugly alongside my moral intuition; and (c) run roughshod over the goddam moral intuition and start taxing Shaquille O'Neal like there's no tomorrow.
(I think Hanson would agree with this general set of options. The disagreement, if there is one, is in his statement that reflective equilibrium "will require [us] to reject some raw intuitions, and embrace some unfashionable conclusions." My sense is that you can move toward reflective equilibrium and remain fashionable.)
5. Anyway, with that in mind, I vote for (b). In particular, I would tinker with the principle of fair equality of opportunity until it included a ban on taxing biology in the name of fairness.
6. The question here is "Why?" I don't have a good answer. I fully acknowledge that I am dodging the tough question here. But does reflective equilibrium give us any guideposts for how we should shimmy, beyond reducing intuitive dissonance?
Again: I feel that I deserve my height (which is really fairly modest) in the same way that I imagine Greg Mankiw feels he deserves his intelligence or his ability to work hard. Does that make me unprincipled? I dunno. All I can say to that is: "What's the alternative?" (I can also offer a highly pretentious quote from Wittgenstein: "If I have exhausted the justification, I have reached bedrock and my spade is turned. Then I am inclined to say 'This is simply what I do.'" Wittgenstein did a lot of crazy stuff, but I get his drift.)
More generally, I'm not sure Hanson should be so quick to reject the impulse to cling to a deeply held moral intuition in the face of radical social planning. As a friend pointed out to me, this is a fundamentally conservative impulse -- standing athwart history yelling stop and all that. Should we embrace the radical social planning instead?