Of course, to some extent this debate is moot. If we ever get to a libertarian world in which these are the only forms of coercion still existing beyond self-defense, etc., we will know a lot more about how liberty actually works and how to achieve it politically than we do now. We will be in a much better position to decide whether to abolish these practices along with all the other vestiges of the welfare state. I should live so long.
Why then debate them now? For the same reason Epstein has been harping on these points for decades. We debate the form of the ideal end stage as part of the debate over whether to take any further steps in its direction.
Barnett clearly wishes to duck the 'and a pony' objection. Let it be so. His explanation of why he finds these sorts of debates interesting and worthwhile is still not fully credible.
An analogy: if you run the mile, it makes sense to think about how to run a faster mile. I don't know what the record is, but someone's planning to break it. Logically speaking - the speed of light and all - it's possible to run a much faster mile. If you had a peculiar turn of mind, you could muse about the sorts of training injuries you might sustain at relativistic speeds. There is a whimsically rigorous appeal to the contemplation of preposterous maxima and minima. But I think it's pretty clear that thinking about running a .01 second mile is not a very helpful way of getting your head into shape to shave .01 second off the record.
The same goes for extreme libertarian fantasies. There isn't any obvious reason why visualizing the end-state will clear our heads about the place we're at. It wouldn't be at all surprising if it did the opposite. Even worse than that: by hinting that modest, practical libertarian policy proposals may hang from a justificatory cloudhook, Barnett leaves himself quite unnecessarily open to a whole class of devastating objections. (That's why I married her, boys. And you can't have her. I found her first, and stole her from another guy.)
As a regulative notion, libertarianism is potent and salutary, in my private opinion. For this purpose, it is best for it to remain simple and cutting and speculatively unencumbered. Barnett's offhand hint that it is even possible "to know how liberty works" orders of magnitude better than we do now is a case in point. To begin with, this fond hope for conceptual breakthrough is pretty incredible. And even if the hint is not nuts, dropping it here is nuts. Another analogy: would it make sense to engineer, down to the level of fine detail, a hyperdrive warp engine to be powered by an as-yet undiscovered energy source? Might as well just say it's going to be pulled by a pony; when we know a lot more about how ponies work.
The response: actually, there's probably a dozen guys at NASA blueprinting all sorts of fancy stuff, without the slightest idea how it could possibly work. The counter-response: and those are the sorts of guys who would spend an afternoon trying to figure out what sorts of running shoes you would need near the speed of light. It's fun to think about stuff. Give your mind a brisk workout. Maybe something interesting will come out of it - but nothing to do with the ostensible target of the investigation, probably.
When I was in college at the good ol' U of Chicago, Epstein's Takings book had just come out and I had some law school friends who were a bit in awe. I sort of dipped into the mighty tome and was - in my immature and legally uneducated way, to be sure - impressed rather against my will with the game athleticism of it all. It's like one of those martial arts stances that is really flashy and shouldn't actually work and probably doesn't really - you know, the ones with names like 'forest bear frosting birthday cake', or 'angry grasshopper typing the one book he's got in him'. I take it this is the status that Epstein's work actually has: everyone ignores it, but something sort of itches the back of your neck when you ignore something that might - just might, in a small way - spin you round.
To complete my thought: I think what Barnett should say - though it's understandable that he doesn't - is that the reason to think about this stuff is that, if you've got a job where you actually get paid to think about stuff like this? And you like to? well, why look a gift pony in the mouth? Also, what the guy said in Hitchhiker's Guide about why he got a prize for Norway: "It's got nice crinkly edges." At their best, libertarian fantasies do seem to meet this aesthetic criterion, in a deductive sort of way. And it wouldn't really make a lot of sense for libertarians to keep in shape by working out on fantasies about the ideal communist state. It would be unseemly.
Ideal end-state libertarianism seems to aim at the ideal end-state of being a delicate, complex and attractive (for those who find it attractive) parlor-game for a bunch of folks who are basically minarchists at heart - and who don't have other hobbies that allow these sorts of things to get worked out of their systems: doing puzzles or designing complicated worlds for role-playing games.
If I don't think a particular utopian scheme is in fact likely to start a foolish revolution that would get us all killed, I guess I don't see why anyone shouldn't be allowed to live in the Cloud Cuckooland of his/her choice.