I don't have the time right now to reply to all of Feser's reply all at once. So I'll post snippets about various points as I get to them. Let's start here:
But there are two problems with this characterization that reflect Wilkinson's failure seriously to address my argument. First, his definition doesn't say anything that an egalitarian liberal or non-libertarian conservative couldn't agree with; indeed, many egalitarian liberals and non-libertarian conservatives do in fact endorse “a relatively small state governed by a rule of law that protects rights to personal autonomy, contract, and private property from within the context of a robust and free market economy.” So Wilkinson's definition fails to capture anything distinctively libertarian. The second, related, problem is that what counts as e.g. “rights to personal autonomy, contract, and private property” and a “relatively small state” — something Wilkinson would have to elaborate upon in order to make his definition informative — is itself extremely controversial, and controversial not only between libertarians and non-libertarians, but even among libertarians themselves. It is therefore no good to point to a commitment to “rights,” “the rule of law,” and the like either as the common core of all libertarian theories or as the one thing that all members of a pluralistic modern society can agree on, because the content of these ideas is precisely what everyone disagrees about. Wilkinson might as well argue that libertarianism, egalitarian liberalism, socialism, and communism are all really varieties of the same doctrine, because they “overlap” in their commitment to “freedom.” Finding some terminology that adherents of various positions all use hardly suffices to demonstrate that there is some substantive view they all have in common; what needs to be shown is that they use that terminology in more or less the same way.
Feser is sort of right; I wasn't putting a great deal of weight on the distinctively libertarian notion of liberal order. I intend to be talking about liberal order, to which I take egalitarian liberals and classical liberal conservatives all to be committed. Political liberalism, of which political libertarianism is a specific instance, is intended precisely to provide a common intellectual framework from within which egalitarians, conservatives, and libertarians can constructively debate and deliberate together in public.
Feser is worried that this or that — rights, rule of law — have no non-controversial specification. I thik he's still missing the point, and wants to argue against political libertarianism as if it's something that it's not. Political libertarianism just isn't a substantive, highly specified doctrine; it's an abtract framework for liberal order. Last night at dinnner Julian suggested that political liberalism is to a particular substantive comprehensive conception something like the scientific method is to a particular scientific theory. Feser's argument has something of the flavor of the claim that the scientific method is a failure (or there is no scientific method at all) because there remains heated, recalcitrant controversy over the possibility of integrating relativity with quantum mechanics.
The libertarian conception of liberal order differs from the welfare liberal version and the conservative versions in exactly the way you would imagine, and in exactly the way I mentioned near the end of my TCS piece. The welfare liberal believes fairly extensive and deep-reaching redistributive and regulatory mechanisms are a necessary condition for stable liberal order. The conservative believes that a considerable number of restrictions on personal choice are required to maintain the conditions for the flourishing of the family, which is a necessary condition for stable liberal order. The libertarian thinks we need neither extensive and deep-reaching regulation and redistribution, nor considerable restriction on personal choice in order for liberal order to hum along quite nicely. Various views about the nature of rights and the rule of law are consistent with the libertarian view.
Feser in general seems to be obsessed with borderline cases, and how exactly to mark out the boundaries of categories. He should relax and acquiesce to the wisdom of ordinary use. While I don't insist on self-identifying as a libertarian, other people identify me as a libertarian because I have a set of views that are characteristically shared by libertarians. That said, I believe in the possibility of a legitimate state. I believe in the desirability of some small-scale redistribution. I am not opposed to all paternalistic restrictions on behavior. I'm no purist. But people have no problem identifying me as a kind of libertarian. If my views shifted along one or another dimension, I might become more like a welfare liberal or a classical liberal conservative than a libertarian. The point on the continua where I would be best classified as something else, like the point of hair-loss at which I man is best classified as “bald”, is obscure. Nevertheless, I don't imagine Feser has a problem identifying the bald. And I don't suppose that people who identify me as a libertarian are confused.
More to come.