Quine and I really differ, not concerning a matter of fact, nor any question with cognitive content, but rather in our respective estimates of the most fruitful course for science [sic] to follow. Quine is impressed by by the continuity between scientific thought and that of daily life -- between scientific language and the language of ordinary discourse -- and sees no philosophical gain, no gain either in clarity or in fruitfulness, in the construction of distinct formalized languages for science. I concede the continuity, but…believe that very important gains in clarity and fruitfulness are to be had from the introduction of such formally constructed languages. This is a difference of opinion which, despite the fact that it does not concern (in my own terms) a matter with cognitive content, is nonetheless in principle susceptible of a kind of rational resolution. In my view, both programs - mine of formalized languages, Quine's of a more freeflowing and casual use of language - ought to be pursued; and I think that if Quine and I could live, say, for two hundred years, it would be possible at the end of that time for us to agree on which of the two programs had proved more successful.--Carnap (1951) as reported by Howard Stein (1992) “Was Carnap Entirely Wrong, After All?” Synthese (reprinted here).
My teacher, Howard Stein, was himself taught by Carnap and so not an impartial spectator to the exchange he reported. But I am fascinated by it, and I hope regular readers forgive me for returning to it (recall); that is, here I ignore all the peculiarities involved in the suggestion that a history of success over time would allow resolution of a debate over methodology (again, recall). My return was prompted by a question posed by one of today's eminent formal philosophers, Richard Pettigrew, who has a student curious about the role of aesthetic norms and how they can oppress. Here, I decided to understand his question rather narrowly, namely the role of aesthetic norms within philosophy. In particular, the role of clarity, which I will treat as an aesthetic norm (even if it may also may be a different kind (?) of norm). That is, I ignore some of the other so-called theoretical virtues that may be thought aesthetic (simplicity, elegance), although what I say may well resonate with these. In particular, I am interested in the role of clarity within analytical philosophy and not as a means to criticize the purported gibberish of Continental philosophy (I have been polemical about this issue in the past; recall.)
Carnap presents himself as the advocate of clarity achieved by the use of constructed languages (we would say, formal methods). Carnap explicitly treats clarity as distinct from the more consequentialist virtue of fruitfulness. (Here I ignore the problems that accompany such consequentialism absent shared background values.) So, while Carnap (and his followers) undoubtedly also believe that pursuing clarity has (many) consequentialist pay-offs, there is an independent merit, an (to use Carnapian lingo, an external) optative value, to the pursuit of clarity.
Clarity here is a property or by-product of formal systems, of constructed languages. Clarity in the hands of Carnap means to capture a kind of demand for transparency in one's inferential practices, one's commitments, and the use of terms (it very much hopes to prevent equivocation and polysemous use). Other forms of (ahh) clarity are not acknowledged as clarity. Again, there are all kinds of other (consequentialist) cognitive and epistemic benefits that are meant to follow from the pursuit of such clarity, but these are not primarily aesthetic.
As an aside on this very last point, Quine had a tendency, as Greg Frost-Arnold has shown, (i) to associate clarity with more general forms of intelligibility. In later years, Quine might argue that (ii) his program (developed in Word & Object) of the philosopher regimenting scientific language to exhibit its ontological commitments, may also be aiming at a species of clarity (about the 'ontology' of science), alongside systematicity. He also (iii) came to think of clarity as a more general theoretical virtue of a system.
Now, I quoted the report on Carnap's exchange with Quine to note that he explicitly recognizes the viability and legitimacy of alternative projects within scientific philosophy broadly conceived. But it can be easily seen that if the only species of clarity that is permitted is the clarity that is a property of formal systems, then emphasizing clarity simply becomes a means to purge alternative forms of philosophy. (If one thinks of the Cartesian and Spinozist use of 'clarity,' there it is a property of ideas. The clearest ideas may -- perhaps this is more true of Spinoza than Descartes -- even lack formal characteristics altogether.) For, it is notable that while in principle anybody can become a formal philosopher or use formal methods, these methods also create, in practice, barriers to intelligibility and understanding to those not in the know.
That is to say, such Carnapian clarity is really a second-order property of an otherwise esoteric, expert practice. This point is not sufficiently acknowledged by contemporary defenders of clarity, who often present themselves as great democratizers, yet don't seem to acknowledge that they are generating barriers to entry into the conversation (and then insist that others must work harder while not allowing for symmetrical demands or the contributions of others--to be sure Pettigrew is not like that!). So, clarity is an important and valuable aesthetic norm in contemporary philosophy. With all expert practices there are risks that their norms can become oppressive; that really depends on institutional context and the ways in which the downside risks of applications are distributed among (expert) participants and non-participants. These risks need to be honestly balanced alongside the many epistemic, moral and cognitive advantages of clarity