This post is based on Andrew Montin's penetrating comments on my post here. I will take some of the issues Andrew raise in future posts:
"In my opinion, Apel does a good job of taking Habermas to task for his notion of the 'weak' transcendental. The dispute circles around the problem of moral justification, but it has implications for the role of philosophy more generally. Apel charges Habermas with the "naturalistic fallacy" of deriving norms from facts in a number of places, but this is how he formulates the criticism in his essay "Normatively Grounding Critical Theory?":
"Although the Habermasian reconstruction of cultural evolution also assumes that prephilosophical lifeworld communication, given its background resources, was *not* in a position to justify the claims to normative rightness raised by conventional morality; thus although the level of discourse we can and must carry out today always already crosses the cultural threshold to philosophical argumentation so that the postconventional situation of argumentative discourse always already belongs to the "forestructure" of our reaching agreement [Verständigung] over... principles of norm justification... the philosophical justification of a principled ethics (including discourse ethics) is nevertheless supposed [by Habermas] to be replaced by *a recourse to the factually functioning ethical life of communicative action in the lifeworld*."
Habermasian formulations such as "we cannot imagine it being otherwise" (which have a definite Rorty-like ring to them) seem to me precisely what Apel is talking about, namely the grounding of quasi-transcendental justifications within the lifeworld. But Apel asks: why does Habermas persist in tracing back such justifications to the context of the lifeworld when his own reconstructive practice already presupposes "a process of lifeworld rationalization" which goes beyond the resources of an ethical lifeworld? Habermas's appeal to the lifeworld to resolve issues of justification is already obsolete - could Apel be suggesting that Habermas himself falls prey to performative contradiction? Certainly he argues in the same essay that Habermas is being openly inconsistent:
"[T]he Habermasian strategy of avoiding a methodological distinction between philosophy and empirically testable reconstructive science seems to me openly inconsistent: I suspect Habermas will have to make up his mind one day whether he wants to persist in the inconsistency or give back to philosophy its genuine *justificatory function*, together with its a priori universal and self-referential validity claims.""