Relativism in analytic philosophy need not be justified as a theory because the relativity of philosophical theories is a fact. The theories which purport to explain the same things are usually in fact mutually exclusive. They cannot all be right, and in fact only those that explain the same thing in common can be at the most partially right together. This is quite the pickle to be in when one wants to assess which theories, if any, are true. Nowhere is this truer than when it comes to theories of truth.
One strategy to get out of this pickle is to assert that there is an independently existing world common to us all, and that truth is the mirroring correspondence of our beliefs with this reality. Searle does this. But there is a problem with this move. For if the world is in fact independent and all that, and we have access to it only through beliefs, then from what standpoint do we relate our beliefs to it? In order to do more than just assume the correspondence somewhere, any comparison of an individual belief against an individual object requires a standpoint from which the two elements in the comparison can be compared, whether that standpoint is literal or virtual; otherwise the comparison will simply presuppose what it seeks to explain. In the case of comparing our minds to an independent reality through the mediation of belief, what standpoint might there be outside of our minds and reality for comparing a “belief” to an “object”? And don’t go down the rabbit hole of “reality as a whole” and “knowledge as a whole”; that just compounds the problem. Some alternatives have been proposed, but none of them seem to work. Otherwise the problem is just brushed away, or not raised at all (again, Searle).
A second strategy is to reject this common independent reality and assert that “truth,” such as it is, is about coherence and/or consensus in conversation, not correspondence with an independently real world; it is, as Rorty says, variously useful social practices. But in this account, it remains undiscussed just what the coherence or consensus is about, or more to the point, what drives and guides intelligent consensus against unintelligent consensus beyond use and disuse on its own terms. That is, would it be true that ‘the Earth is the center of the universe and all bodies revolve around it’ if every human consented to this idea under a coherent theory, even though “in fact,” in an “independent world,” the Earth goes around the sun? It’s not just that the math is easier; this “fact” of the “independent world” can be tested and proven using nothing more than the tools of crude, everyday experience that the opposite belief uses to say it doesn’t. Just a little more ingenuity is required. So the coherence and consensus view must tacitly import an independent reality at some level in order to avoid its own absurdity, i.e. that patently false beliefs can be endorsed as true, and are therefore “true,” by the new criteria of consensus. In other words, “consensus” and “coherence” leaves us with the inability to explain an obvious feature of our crude, everyday experience, i.e. sometimes consensus is wrong, even with coherent theories. But how can wrong ideas be true? Rorty’s “pragmatism” has no answer beyond asserting that ‘this pickle is ok just as long as we are comfortable with it.’ But not everyone is, hence again the problem with consensus.
A third way out is to say that an “independently existing world” is a posit, an idea, or a background assumption that interlocutors make in order to give them both reason to strive for common ground and a basis for saying that they have reached a good one in their consensus on coherent beliefs. Searle does this even as he dogmatically draws an ontology from it while saying that he doesn’t. Rorty, somewhat reluctantly, endorses the first part of the move while repudiating the second, namely the ontology. Both hedges are critical. For on the one hand, if this “independent common ground” was not posited in advance of inquiry, there would be little motive for engaging in it—or perhaps better, little hope that it would amount to much. And on the other hand, if it were not posited as an arbiter at the end of inquiry once consensus has been reached, there would be no basis for saying that a true belief, as opposed to an arbitrary or incorrect one, has been reached. In this case how would the “we” assess “good”, “useful” or “true”? Consensus and coherence or independent world? On “independence” and “truth” as a double-barreled rhetorical strategy both sides can generally agree. But this agreement will not do. For having agreed on this point both parties are only left in exactly the same position with which they started, vying against one another, namely, against the specter of whether this independent world actually exists as it does, and whether truth is correspondence of our beliefs with it, or is it just consensus and coherence in conversation.
Given the terms in which the debate is usually posed, there seems to be no solution, and just because this question can be brought up on a case by case basis instead of all at once doesn’t change the nature of the problem. Though perhaps this fact changes its traction as a real problem to be solved, once the rubber really hits the road.