“I do not know how to refute an incredulous stare” — David Lewis, philosopher and logician

We all have those sliding doors moments: times when we wonder what if we hadn’t missed that train, if we had proposed to that person or if we had bought that lottery ticket. For most of us these are idle speculations on how things might have played out for us — reflections on the roles played both by choice and contingency as they shape a human life.

For the philosopher, of course, speculation is never idle (even if, as Russell wrote, an idea can strike one in a time of idleness). And there is no idea so counterintuitive that its batshit craziness cannot be redeemed by translation into the respectable language of analytical philosophy. The apparently insane thesis being, in this case, the claim that to make sense of “what might have been but isn’t” we must assert that there are real worlds in which what isn’t, actually, is. 

There really is, according to some, a universe in which a version of me is enjoying a front seat view of an hilarious and politically relevant Led by Donkeys caper, in the company of my bizarro fiancée, a virginal aspiring actress called Norma Jean Baker. True that universe isn’t this one — but it is no less real for that (they would argue). And it would be chauvinistic to suggest otherwise: why favour this world on the arbitrary grounds that it is real to us over an alternative world which is similarly real to those who inhabit it?

Such speculation, which the metaphysicians call modal realism, is associated with the late American logician, David Lewis. It’s fair to say that Lewis’ colleagues did not unanimously endorse this alchemical attempt to grow a rich metaphysics from the logic of the word “if”; hence the quote which introduces this piece. Just how do you refute the incredulous stare? 

My sympathies here are with both the starer and the stared at. I have theological grounds for thinking that God can think of any possible world in such a way that makes that world real to Him, and if it’s real enough for God then surely that’s good enough for the rest of us? But the question generalises: can an incredulous stare be a legitimate argumentative manoeuvre? I suggest that it can, and that in certain conditions, the incredulous stare, and the ad hominem strategy more generally, are creative contributions to the conversation, whether conducted in the rarefied context of the academic symposium or the arguably more demotic circumstances of the Twitter pile-on.

Think of the curious case of the famous detective. Sherlock Holmes is an impressive (if lucky) sleuth but a pedestrian logician. When he tells you that from an indentation on your right middle-finger he can deduce that your alibi for the murder is entirely bogus, he is either outright scamming you or revealing that he has no appreciation of what counts as a genuinely deductive inference. A deductively valid argument is one whose conclusion follows axiomatically from its premises. In other words, the conclusion tells you nothing you didn’t already know. It is, if you like, an exercise in cognitive housekeeping, of minimal value when it comes to the fighting of crime in Victorian London. If Holmes were in fact restricting his reasoning to the deductive model, then Moriarty could sleep soundly at night.

What the drug-addled fraud of 221B Baker St is really engaged in is inductive reasoning, where the premises of an argument serve as good evidence for its conclusion. A well-crafted inductive argument sacrifices complete formal rigour for the consolation of saying something new. The problem is that the inferential chain might have a weak link. Were Conan Doyle to insist on verisimilitude his most famous creation would often be made to look like a bit of a prat. (I would point out that despite their geographical and chronological proximity, he never managed to feel the collar of Jack the Ripper).

Briefly, what Holmes’ charlatanism shows is that there are many and different forms of argument, and what counts as appropriate will vary between contexts.

We must remember that to argue is to indulge in a practice, and like all human activity this requires constraints, conventions, customs and norms. When people announce that they are entitled to an opinion it is perfectly fair to point out that this is true only up to a point. If you believe p and accept that p logically implies q you are not entitled to a belief that contradicts q. Similarly, if you announce a theory and evidence is adduced which disconfirms that theory you are not entitled to shrug that off. These are not merely errors of fact or logic, they are also, surely, ethical in character, constituting as they do breaches of dialectical etiquette. 

So, what of the incredulous stare, or the caustic put down? I submit that there is room for these in the general philosophical to-and-fro, and that in certain situations they can do some intellectual heavy lifting. To make a Wittgensteinian observation: they are genuine modes of expression and therefore qualify for inclusion in the language games which comprise the philosopher’s form of life. And if your interlocutor is as recalcitrant as a Remainer, or as beguiling as a David Lewis, the disbelieving stare might be the most valuable resource in the intellectual toolbox. 

I’ll conclude with an example. Sydney Morgenbesser was a philosopher from New York, made famous by his knack for the philosophically relevant one-liner. At a conference a speaker made the claim that in the English language instances of two negatives combining to make a positive were commonplace, whereas it is unheard of for two positives to combine to make a negative.

From the back of the lecture theatre came Morgenbesser’s reply, in the accent of the Lower East Side: “yeah, yeah”.

The incredulous stare, in verbal form, deployed to devastating effect.