There’s a kind of pragmatism, call it Carnapian pragmatism, that concerns the adoption of languages. More specifically, Carnapian pragmatism, as I am using the term, combines two theses: (1) there are no a priori rationally indispensable languages, and (2) the adoption of a language ought to depend on the weight of the various benefits that speaking that language confers on one and one’s community. (1), rules out, for example, the a priori indispensability of a language involving material substances that persist through time and underly change. That is, of course, compatible with that language’s being as a matter of fact the obviously best language in which to (e.g.) conduct inquiry. (2) gives us a criterion scheme for choosing among eligible languages.
Now consider the following claim, a rough first approximation: there are some truths that one ought never to come to believe, because they involve defective concepts. Everyone, I think, will grant that there are some truths we ought not to come to believe for some significant sense of ‘ought’, perhaps because they would be too damaging or morally corrosive. But suppose the ‘ought’ is the ‘ought’ of inquiry: given the goal is furthering inquiry, one ought to φ (in general I don’t think this will be what is called the epistemic ‘ought’). The claim, then, is this:
(*) There are some unambiguous truths p (where an unambiguous truth is simply true, and thus not also false) and subjects S such that (A) S is warranted in believing p, and (B) S has considered whether p, but (C) S ought not to believe p because p contains (or is expressed with) a defective concept.
Another way of putting things: are there concepts defective from the point of view of inquiry not just because they have no instances (or, more generally, cannot be used to express positive truths)?
I consider (*) to be stronger than Carnapian pragmatism. According to Carnapian pragmatism, there are languages we ought not to speak in view of what best furthers inquiry. Important progress in science can be made by hitting on these languages. But this thesis is just a thesis about language, and not about rational belief. Carnapian pragmatism does not forbid you from believing content composed of or expressed by bad concepts. As a view, it has a large amount of prima facie plausibility, whereas the claim of the previous paragraph looks pretty controversial from the first.
There are some concepts it would be better if we did not have, if only because they add clutter without doing much corresponding work for us. Hirsch’s incar and outcar might be good examples. Other concepts are more pernicious, because they encourage thoughts it would be prudentially better for us not to have. Slurs might be one example here. But if our only goal is inquiry, are there really concepts with which we can express truths, but where those truths simply ought not to be believed? It is just not plausible that, where we find ourselves thinking about incars, and we realize some true thing about them, that we ought not to believe that true thing. It’s just that it’s unfortunate that we ever set out thinking in terms of incars, since that’ll mostly be a waste of our intellectual resources.
A variation on Prior’s tonk might be the kind of thing we’re after. It’s characterized (incompletely, for present purposes) by its introduction rule (from A, infer A tonk B) and its elimination rule (from A tonk B, infer A). But these rules don’t give us any truth conditions for tonk, so let’s stipulate some: A tonk B is true iff A is true or B is true. Suppose we have a sentence like ‘Grass is green tonk Gibbard invented penicillin’ (call it G). G is true, since the corresponding disjunction is true. But we ought not to believe G, since then we would be “licensed” to infer that Gibbard invented penicillin, a manifest absurdity. So perhaps this is a counterexample. I don’t think it is, though. Though it is true that G analytically entails that Gibbard invented penicillin, we are often not permitted to believe even what’s logically entailed by what we believe, as in preface cases, or where we have contradictory beliefs (not just anything goes in that kind of case). Similarly, though the concept is characterized by certain sorts of inference rules, it is impermissible to infer according to those rules, because we know that a huge variety of tonk-inferences do not preserve truth, and do not even pretend to.
To forestall an objection: we still have the concept tonk even if in most cases we don’t infer according to its characteristic rules, if only because we can argue about it and have good reason to say things like ‘tonk is a dumb concept’ with complete justification (compare Williamson on McGee and modus ponens). That is, I think I have at least one tonkish belief (G), though I haven’t yet inferred that Gibbard invented penicillin. So, we might be permitted (required, if the truth and our warrant are obvious enough) to believe truths expressed with this version of tonk, though we would also have to be sure not to make risky inferences.
Here’s a worry about that response to the tonk variation. Tonk will still differ from incar, because in worlds where incars are extremely important, truths about them become very important. That is, there are some possible beings for whom it would be useful to think with incar. But with tonk, no matter which possible world and which possible beings, or beats it in view of inquiry. Or and tonk make the same contribution to truth conditions, but with or, you need not worry about making the inferences that come with possession of the concept; with tonk you need to be on your guard. So or will always be at least as good as tonk. While I agree, I don’t see how this gets us (*). It would be better to reason with or than with tonk, no doubt about that. But ought we really to disregard the tonkish truth, just because or does better? That just doesn’t follow. The worry, then, is just an instance of Carnapian pragmatism, and does not establish (*).
(*) is an exciting claim, while Carnapian pragmatism seems old hat to me. It would be a way of combining conservatism with revisionism: “granted, the people here are saying true things, but what they’re doing is nevertheless defective”. So, it would be very interesting to find the truths it claims are out there, though I haven’t yet found any. For my own part, I’m inclined to think something like this: from the point of view of inquiry, anyone is permitted to believe any unambiguous truth for which they have undefeated warrant. If, for example, theological discourse is defective from the point of view of inquiry, it is defective because its positive claims are all of them false, since they would involve a concept with no instances. I don’t know if I have more of an argument for that claim than the ridiculousness of conceding to someone that some claim is true, and they have great reason to believe that claim, but even so they oughtn’t to believe it. We all just need to be careful about what we do with even the truths we believe. That might sometimes be difficult, practically speaking, but it seems always at least possible.
(Thanks to Umer, Boris, Zoe, Paul and Nick for the interesting discussion much of which I’ve translated here.)