The full audio of Brandom's fifth lecture, along with the reply and the full Q&A section, has been posted to the place the old version was at. I figure this is of interest to some, and wouldn't want it to get buried in an old comment thread.
Hopefully I'll get around to listening to the full version (and the final lecture) sometime before the sun becomes a cold, dark lump of coal the size of your forehead. But no promises!
edit: I have listened to the full version, and have started working through Priest's "An Introduction to Non-Classical Logic". Which has been my first formal introduction to modal logic (though I was of course not entirely ignorant of the stuff before now, my "Logic" course didn't go past the predicate calculus, so I'd been neglecting actually sitting down and working textbook problems for anything more than that). I get what Brandom's been saying about "the modal revolution" now; this stuff is neat.
I'm not sure how much Brandom's claims about "the intrinsic logic" of e.g. intuitionist logic being classical S5 really amount to. The claim seems to boil down to saying that for any autonomous discursive practice, even one in which "Not not A, ergo A" doesn't generally hold as a form of valid inference, you can say how to draw inferences according to classical S5 rules; any autonomous language game is VV-sufficient for laying out classical S5's inferential rules through a semantics that speaks only of commitment and entitlement. But this does not strike me as particularly impressive; there would still be inferences in the discursive practice whose form classical S5 would countenance which the discursive practitioners would not recognize as valid, so it strikes me as odd to say that the "intrinsic logic" of the discursive practice is classical S5. Whatever purpose "intrinsic" logic serves, it doesn't seem to have much of a relation to the inferences reasoners draw, and so it seems like a rather beggarly "intrinsic" feature of their practice. If logic isn't behind the validity of inferences, I don't see what it can be said to do at all.
I don't think there's anything here that Brandom would disagree with; he said in an earlier lecture that he doesn't think the question of "Which is the true logic" is a good one, since various logics can be used to express various sorts of inferential commitments. But then I'm left wondering what calling classical S5 "the intrinsic logic of most familiar logics" is supposed to mean, if it's not supposed to be calling classical S5 "more true" than other logics -- more closely related to our inferential practices, or somesuch. For instance, on page 2 of the lecture handout:
Fact: The incompatibility semantics over standard incompatibility relations with these semantic definitions of connectives validates classical propositional logic.What is that supposed to mean, if we're not interested in the question of "Which is the true logic"? In what sense can classical propositional logic be "validated" short of being "the true logic"? Is this supposed to be an explanation for why classical logic came along so early, and has been so widely-liked, or something like that? (If so, it strikes me as a bad effort -- classical logic has simple truth-tables, and both "the law of excluded middle" and "the law of noncontradiction" have the support of Aristotle (and most of the tradition), which I think nicely accounts for why non-classical logics always smell a little fishy. But I suspect Brandom doesn't mean to be addressing this question, either. I just don't know what "intrinsic logic" is supposed to signify. Perhaps he's claiming that classical S5 can be worked out purely from talk of commitment and entitlement (and not of truth etc.)? But then I still don't see why "intrinsic logic" should be a good title for this feature of classical S5.)
This is to set to the side that, as I understand it, paraconsistent logics don't have classical S5 as their "intrinsic logic". Whatever the "validation" of classical logic is supposed to amount to, I suspect that this is a serious barrier to it.
On a more positive note: I liked the stuff about holism. Fodor comes under attack from yet another front; suits me fine. I am curious what Brandom's argument for holism entails for a Tarski-style theory of truth (along Davidsonian lines), since in a Tarski-style theory the truth-conditions of a sentence are derived from semantic properties assigned to sub-sentential units, that of satisfaction; the satisfaction relations are the axioms from which the familiar T-sentences are drawn as theorems. Tarski-style theories of truth are compositional. (I think I have this right; I should probably go back and read some of the earlier Davison essays to brush up on this.) Brandom's semantics is not compositional, though it is recursive. "It is holistic, that is, noncompositional, in that the semantic value of a compound is not computable from the semantic values of its components. But this holism within each level of constructional complexity is entirely compatible with recursiveness between levels. The semantic values of all the logically compound sentences are computable entirely from the semantic values of less complex sentences." I suspect that this is not a difference which makes a difference. The Tarskian details that lie behind Davidson's "Convention T" do not seem to play much of a role in the interpretive process; ""S" is true-in-L IFF P, where "P" is a translation of "S" into English, or simply S if L=English" does not seem to need any adjusting if one mucks around with the axiom system Tarski used; McDowell argues in one of his essays ("In Defense of Modesty"?) that intuitionists can make use of a Tarski-style theory of truth as a theory of meaning despite their disagreements about logic, contra Dummett & Wright, and I should think the same holds here: The important part of "Convention T" remains unassailable, though some of the things Davidson wrote about compositionality might need revising.