‘A philosopher’, Stephen Yablo quips, ‘is someone who says here is the thing that’s happening everywhere, all the time, throughout human history, but it’s really hard to think of a good example’. I have met Yablo, David W Skinner Professor of Philosophy at MIT, at his home on Washington Street in Cambridge, Massachusetts. We are sitting in a warmly-lit room next to the kitchen, featuring a comfortable but very sorry-looking couch that, as we talk, I pick at incessantly. It is a very hot day in August, and Yablo is across the table from me, wearing a t-shirt, shorts, and a messy hairdo. His expression tends towards the wry, but his hand gestures towards the expressive, at the moment bordering on the Italian. The touch of irony and self-deprecation in Yablo’s definition of the philosopher – he is one himself, of course, and married to another – are, if not par for the profession, unsurprising for Yablo personally. In one article he cautiously suggests that some philosophical ponderings are ‘just a teensy bit ridiculous’; in a parenthetical aside elsewhere, he wonders if philosophers of his temperament are of the self-hating kind; in a lecture, he calls a distinction ‘a little superficial, so it’s… just right for me!’. The lightness of these remarks, however, belies their depth: they are the reflection not only of a certain personal attitude, but a philosophical one as well. Take the lecture joke, for instance. A superficial distinction might be contrasted with one that, in Plato’s phrase, ‘carves nature at its joints’. But why think that philosophy should aim at the latter? Might not concepts and distinctions that make sense of how the world seems to us, of its appearance to observers who have our outlook, in the end, serve us better?
I first stumbled across Stephen Yablo towards the end of the second year of my degree, while taking philosophy of mind. The essay was ‘Mental causation’, one of his earlier efforts to account for how mental states – such as pain, contempt, love, and belief – could cause physical events. It’s clear, if anything is, that they do. As Yablo himself puts it elsewhere, ‘Smirking, beaming, moping about, shivering in anticipation, raising a skeptical eyebrow, favoring a tender limb – these are just an inkling of the human phenomena making no sense in a world where thoughts and feelings keep causally to themselves’. But philosophers have found it hard to explain how the mind can be causally efficacious. Isn’t it really the firing of neurons that causes things to happen?, they ask. If all the happenings in the world can be accounted for by physics, the problem runs, what work is left for mental states to do? I’d like to say I was immediately convinced by Yablo’s answer to these questions – that the metaphysical connection between mental states and physical states is tight enough to preclude causal competition between the two – but in fact I didn’t make it that far. Yet, it now seems, a subconscious trace had been left by that early exposure. I don’t remember how it happened, but I do know that several months later, by the time revision season had rolled around, my desk and computer desktop were cluttered with Yablo’s writing.
Reading Yablo can be an electrifying experience, if electrical charges passed through you at the rate of several pages per hour. His writing resembles to a remarkable degree Edgar Wright’s film Scott Pilgrim vs The World: it is stylish, witty, energetic, unpretentious, original, fun. (Scott Pilgrim is even set in Toronto, where Yablo is from.) One chapter of Yablo’s 2014 book, Aboutness, is a breathtaking example of this flair: in 18 fairly short pages, Yablo discusses, amongst other things, (i) the point of uttering half-truths, (ii) the existence of numbers, (iii) mental content, (iv) scientific laws and models, (v) the existence of fictional entities, like Pegasus, and (vi) metaphysical and logical impossibility. In fact this kind of point-to-pointing is rare for Yablo, who often lays down objection after objection, even when his first is damning enough. More common, rather, is for the points themselves to be expressed very tightly, or (at least initially) by way of metaphor. Causes shorten the path to their effects; some aspects of meaning float free of truth-conditions; sentences acquire newly exposed flanks, or march right up to sceptical possibilities; the technology for capturing a phenomenon instead strangles it in the cradle; a theory’s problem is not only that it uses a cannon to kill a mouse, but that it misses the mouse and hits neighbouring mice instead. One paper, in a riff on Bertrand Russell, discusses the possibility that ‘an entire species of much-beloved and frequently deferred-to entities, has been stolen away, leaving behind only persistent appearances’. The sections following the quote are called ‘Means’, ‘Motive’ and ‘Opportunity’. The crime? Getting the representational benefits of abstract objects – like numbers, properties, events, sets, and models – without needing to say that such things exist.
Yablo by now has worked in most core areas of theoretical philosophy, including metaphysics, epistemology, mind, logic, and language. The only notable exception is ethics (which Yablo at one point in conversation calls the genuinely deep stuff). An online biography, however, says that he started as a logician, before branching out. But, I figure, no one starts as a logician. This, it turns out, is pretty near wrong. ‘My father’, Yablo tells me, ‘was constantly calling me on alleged logical errors. I used to feel that can’t be right, so I did spend a fair bit of time trying to catch my father in contradictions.’ He also remembers reading his mother’s old copy of Descartes’ Meditations. ‘I got interested’, he says, ‘in the question of possibilities that nobody takes seriously but were not really defended against, and the peculiar horror of something happening that we hadn’t really thought about’. The young Yablo proceeded to write a short essay about the possibility of gravity giving out. This wouldn’t just be surprising to us, he figured; it would upset us more deeply. On another occasion – still ‘embarrassingly young’ – Yablo wrote a piece called ‘Individualism and the Masses’, in response to a book found on some basement shelf about the Canadian national identity. ‘It made no sense’, Yablo admits. ‘It was this rhetorical blabber that I picked up somewhere.’
Yablo’s philosophical development continued apace in high school, where he wrote a letter to an early idol, the behaviourist BF Skinner, ‘partly to do with thinking he was making things too simple, which were really complicated’. (Skinner wrote back, Yablo says, ‘which was really cool’.) He also ran into Quine, Carnap, and at least one niche treatise on logic and fatalism, although, curiously, he didn’t know that the writers he was reading were philosophers. ‘I don’t know how I could have failed to appreciate there was such a thing as philosophy, when I had read Quine’s Philosophy of Logic’, Yablo says, ‘but fortunately I ended up going to the University of Toronto, which, after Oxford at the time, and maybe even still, was the biggest English-speaking philosophy department’. His initial idea of majoring in English was very quickly abandoned. At Toronto, Yablo says, of his forty courses, about thirty-two were in philosophy. ‘And they had that many different philosophy courses. I took the philosophy of Bertrand Russell, et cetera. I was really interested.’ One of his professors, Hans Herzberger, was especially influential; and it was in Herzberger’s class that Yablo was first exposed to Saul Kripke – the prominent philosopher of language – who Yablo says has been his most significant intellectual influence. Yablo recalls being blown away, back in 1978, by Kripke’s now-famous ‘Outline of a theory of truth’. ‘I thought it was the most amazing thing I had ever read in my life’, he says, ‘and I assumed everyone else thought so too’. Yablo’s exposure to Kripke led him into an awkward encounter with an aging Alfred Tarski, the famous logician, two years later. Spotting him at a party, Yablo asked Tarski what he thought of Kripke’s work on truth. ‘He basically just looked at me’, Yablo says. ‘It seemed to be a contemptuous look. He didn’t answer, he just turned and walked away.’
Kripke’s influence on Yablo is indeed apparent, both philosophically and temperamentally. For one thing, Yablo has sought in several papers to defend and deepen the theory of meaning that Kripke sets out in his seminal Naming and Necessity, and has emerged as one of Kripke’s ablest interpreters (and, occasionally, critic). A recent paper on nonexistence is a case in point. The problem discussed in the paper concerns what are called ‘empty names’, names, like ‘Pegasus’ and ‘Sherlock Holmes’ that don’t seem to refer to anything – names, that is, which fail to name. Such names are sometimes thought to be a terminal problem for ‘Millian’ views, like Kripke’s (and John Stuart Mill’s), which take the meaning of a name to be exhausted by whatever the name refers to. For example, the meaning of ‘Jane Austen’ is taken to be simply Austen herself. Crucially, on Millian views, the meaning of a name does not involve any descriptive content: ‘Jane Austen’ does not in part express ‘the author of Pride and Prejudice’. Millianism indeed seems to get a lot of the intuitive data right; for instance, as Kripke argues, if ‘Jane Austen’ partly meant ‘the author of Pride and Prejudice’, then, amongst other problems, how could ‘Jane Austen might not have written Pride and Prejudice’ be true? The issue, however, is that, if ‘Jane Austen’ means Jane Austen, then ‘Sherlock Holmes’ must mean Sherlock Holmes… but there is no such person! So does ‘Sherlock Holmes’ therefore lack meaning? And, if it does, then wouldn’t sentences containing ‘Sherlock Holmes’ themselves be meaning-deficient? Yet some such sentences, like ‘Sherlock Holmes does not exist’, are clearly not only meaningful, but true.
To resolve the difficulty, Yablo seizes on an enigmatic remark Kripke makes in a paper on the topic, that ‘whatever bandersnatches may be, certainly there are none in Dubuque’. Kripke claims this is heard as true because it really says ‘that there is no true proposition to the effect that there are bandersnatches in Dubuque’. Although Yablo rejects this particular claim about what the sentence says, his paper defends (what he takes as) Kripke’s underlying idea that we should be looking for something the sentence can be heard as saying that is true, even if it fails to express a proposition about Sherlock Holmes. Yablo’s own suggestion is that even though ‘Sherlock Holmes does not exist’ cannot be true about Holmes, it might nevertheless be true about a different subject matter: what does exist. It is plausible, Yablo argues, to suppose that even if ‘Sherlock Holmes’ is itself strictly meaningless, the term still functions evocatively, recalling certain properties that we know Holmes, if he existed, would have. The next step lies in noticing that none of us – ‘us’ comprising you, me, the planets, and so on – has those properties; and finally, that each of us has properties that Holmes, on the hypothesis that he exists, doesn’t have (for instance, you and I were born too late, and Venus weighs too much). It is this last claim that Yablo maintains is the content asserted by ‘Sherlock Holmes does not exist’: the sentence says that each existing thing has distinctive properties – different in each case – such that, even if Holmes exists, he is at any rate not that particular thing. And since it is, in point of fact, true that each of us has some such properties, we hear the sentence itself as true.
Yablo bills his argument as a development of Kripke’s position on nonexistence, one ‘making use of basically Kripkean materials’. But even if that’s not true, it is certainly one that leverages distinctly Yablovian materials, such as subject matter and the ‘even if’ locution itself. Indeed the paper, beyond its contribution to the philosophy of language, doubles as a front in the war that Yablo has been fighting over the last decade (Aboutness being the dazzling blitzkrieg campaign) in support of taking seriously subject matter as a component of meaning and reconciling philosophers to ways as a new primitive in metaphysics. Neither of these notions is complex: a sentence’s subject matter is just what it’s about, and ways are, well, ways (as in ‘red is a way of being coloured’). Yet they shed an astonishing amount of light on a wide range of familiar philosophical problems, including some of the most baffling. As another example, take Wittgenstein’s question, ‘what is left over if I subtract the fact that my arm goes up from the fact that I raise my arm?’. It is at first very difficult to get a handle on what Wittgenstein is up to. But Yablo encourages us to think about it in the context of a host of more ordinary examples. To offer a few: we all agree, with the possible exception of Lizzy; he won, unless it turns out he cheated; the twins are identical, ignoring their freckles; all was well, but for the cancer and impending divorce; his writing is exactly like lightning, except in respect of speed. Each of these sentences involves logical subtraction (we start with perfect agreement, then subtract Lizzy’s agreement); the peculiarity of Wittgenstein’s question is simply that the implicated remainder – of ‘my raising my arm’ minus ‘my arming going up’ – isn’t well-defined. As for how to calculate remainders: to heavily oversimplify, one finds the part of the first sentence that’s silent on the subject matter of the second. Other possible applications of the philosophy of aboutness include, to reel off a few: verisimilitude, partial truth, scepticism, parthood, modelling, confirmation, vagueness, and permission.
In any case, Kripke and Yablo don’t just share similar views in the philosophy of language. Yablo also feels a strong affinity with a certain attitude he detects in Kripke’s writings, of thinking that – as Yablo writes in a review of Kripke’s Philosophical Troubles – in philosophy, ‘there is no end to our troubles’. (Naming and Necessity famously concludes, ‘I regard the mind-body problem as wide open and extremely confusing’.) ‘My feeling’, Yablo tells me, ‘has always been one of finding philosophy really hard’. He says he picked up this attitude when he was still a student, and that it’s never left him. ‘Part of what happened’, he says, ‘was that I was taught by a lot of people who thought it was almost definitional of philosophy that it should be really hard. People at Berkeley’ – where Yablo attended graduate school – ‘had the idea that philosophical problems are part of the human condition, and if you think you’ve solved one, that just shows you’ve misunderstood it’. Yablo gestures at Kant’s line (as he does at the very end of Aboutness) that reason sets problems for itself that reason cannot solve. ‘So yes, I do find it hard’, he says, ‘but one can definitely take this too far at times. I remember as a grad student at Berkeley, when David Lewis came and gave a talk about causal explanation, that everybody, it wasn’t just me, found it strange that he took himself to have “solved” something. I thought, well, then he’s basically just an engineer, not a philosopher. I outgrew that attitude, let’s hope, but I do probably have more of a thing for the mystery of philosophy than is common or popular these days. I think it should be hard. You should never really feel you’ve got a grip on it.’
Yablo’s sense, not just that philosophy is hard, but that it is an important fact about philosophy that it is, in fact pervades his work quite widely, sometimes in subtle ways. In the preface to Thoughts – the first of Yablo’s two essay collections (the other is called Things) – Yablo writes that, like David Lewis, he ‘set out to be a piecemeal, unsystematic philosopher’. He adds that, so far, he seems ‘to be doing a much better job of it’ than Lewis, who ended up the greatest philosophical system-builder of the twentieth century. It is not until I talk to Yablo, however, that it becomes clear to what extent this claim is not a confession or, perhaps, an apology; it is in a real sense a statement of principle. It is understanding this that lets one start to see the connections between writings that might otherwise not seem to hang together. ‘It’s always mattered to me’, Yablo says, ‘what’s worth worrying about and what’s not worth worrying about. Two opposite things that bother me about a lot of philosophy is, you know, trying to solve problems that are part of the human predicament – you shouldn’t have to, or want to, solve them – and taking seriously problems that are just an artefact of—’. At this point Yablo is interrupted by his dog Daisy, who bursts yelping into the room. Daisy quickly takes a liking to me, or at least the taste of my hand, and for the next hour, before Yablo’s son Isaac comes in and takes her, I never quite conquer the suspicion (despite Yablo’s assurances) that at any moment Daisy might get hungry and take a bite.
Once things have settled, Yablo picks back up, grasping for the right way of putting his objection. ‘So most of my upbringing was, certain problems are much more serious than people give them credit for, like scepticism’, he says. ‘But then the other side of that is there are certain problems that just seem like they are artefacts of habits that philosophers have got into, and they’re really just like…’ He trails off. ‘Okay, here’s an example’, he says, starting over. ‘Quine says, “you decide in favour of mathematical objects by realising you need to quantify over them when you’re doing math”, and he goes, “I’m just deferring to what these practitioners of a much more successful discipline are doing”.’ Here Yablo is referencing a classic argument, by Harvard philosopher WVO Quine, for the existence of numbers, which supposedly takes as its starting point the simple observation that scientists use numbers, and claims on this authority – the authority of science – that numbers exist. But physics only uses sets up to a certain cardinality. So what does Quine say about discourse that makes use of higher-level mathematical entities? That he regards it ‘only as mathematical recreation and without ontological rights’! Yet, as philosopher of mathematics Penelope Maddy points out, no actual scientist attaches the slightest ontological importance to the distinction between applicable sets and inapplicable ones; they don’t even try to look for the line. ‘Basically what Quine does’, Yablo says, ‘is he goes around, locates some aspect of practice that he can pretend to defer to, and then where it doesn’t actually have the form that he likes, he acts like the practitioners are not applying their own principle consistently. There has to be a word for this… this self-serving, hypocritical, “I just do what they say, unless it’s not what I want, in which case I correct in light of what they would have said if they’d seen things as clearly as I do”.’
As Yablo goes on, the connection between this complaint – of, as one might have it, scientistic sanctimony – and the earlier point, that philosophers tend to misrepresent the difficulty of problems, becomes clearer. One way of putting it might be that both practices exhibit a peculiarly philosophical arrogance, involving, on the one hand, the steamrolling of difficulties and complications that threaten one’s own view and, on the other, a blindness to the merits of other positions. (Or as Bernard Williams and Michael Tanner once wrote about GEM Anscombe, ‘she combines a commonsense bluffness against other people’s distinctions, with the most sensitive indulgence to the niceties of her own’.) Another expression of this attitude, Yablo says, comes in the tendency to ‘pull down linguistic facts from on high’, as if they univocally supported one’s own position. ‘There’s this pulling rank that drives me completely nuts’, he tells me. ‘So first, you’re not supposed to play fast and loose and just make stuff up. I get that and agree with it. But there’s an opposite danger, isn’t there, of getting unnecessarily dismissive and carrying on like the only real grown-up in the room.’ Another manifestation is in the way some philosophers have of declaring rival positions self-refuting or literally meaningless. Yablo references, for instance, one paper that says a certain view about content involves a ‘transcendental contradiction’. ‘I just remember thinking’, he says, ‘that there’s so much ingenuity wasted when things go that far. The idea that there are hidden contradictions in rival views, in general, really bothers me. It’s not a bad enough fate for those views just to be seriously mistaken?’
This opposition to oversimplification, of language and of the world, shines an interesting light on Yablo’s work. Daniel Rothschild, another philosopher, wrote in a review of Aboutness that one could see the book in different ways. Some, Rothschild said, might see it as an extended defence of the non-existence of numbers and other abstract objects, but he himself prefers to regard it as ‘an advertisement for a new way of thinking about meaning’. When I quote this line to him, Yablo is very quick to say his view is much more Rothschild’s. ‘A lot of the distinctions drawn in Aboutness’, he says, ‘are attempts to rehabilitate things that are held not to make sense’. Indeed this focus on meaning Yablo takes to animate much of his earlier work on the meta-ontological question of which first-order ontological debates (debates about what exists) are worth pursuing. In 1998, Yablo published a paper ‘Does ontology rest on a mistake?’ that advocated ‘figuralism’ about certain abstract objects, like numbers. He suggested that discourse involving abstract objects wasn’t to be taken literally, and that talk about numbers doesn’t straightforwardly commit me to the existence of numbers any more than the sentence ‘the average star has 2.4 planets’ commits me to the existence of the average star, or the expression ‘he’s got a lot of smarts’ commits me to the existence of smarts. The language of numbers, Yablo claimed, has presentational and representational advantages: it lets us say things we perhaps couldn’t otherwise say; and it lets us represent the world more efficiently. As he points out in a different paper, ‘That known truths cry out for numerical rearticulation could be heard less as a theoretical argument for the objects’ existence, than a practical argument for postulating them quite regardless of whether they exist’. (Numbers are, in that way, rather like God.)
This view has evolved over the last twenty years: from figuralism, to ‘presuppositionalism’, to, most recently, ‘if-thenism’. The claim that numbers-talk is figurative has been dropped; now the idea is that the existence of numbers is presupposed by, so doesn’t enter into the assertive content of, sentences that refer to numbers. Throughout all these iterations, Yablo says, ‘the issue has always been: what kind of talk involves you in what? It’s really more about how to organise your intellectual resources, and when you’re committing yourself on this, while not committing yourself on that.’ The project has also been to offer up a positive account of what it might be for a question to be objectively moot, for there to be no fact of the matter. He calls his position, in a catchy label, quizzicalism. In an unpublished paper (‘do not quote or even think about too much’, its description reads), Yablo suggests that the appropriate attitude towards mathematical ontology is one of insouciance: ‘don’t know and don’t care, and come to think of it, don’t really see that there’s an issue here’. ‘Sometimes it seems’, he tells me, ‘that ontologists are just fighting over the appropriate form of disdain to show towards ontological questions about numbers’. He contrasts his view with the position of the ‘easy ontologist’, whose characteristic claim is that it’s trivial that numbers exist. ‘I have taught seminars where I’ve tried to sort this out’, Yablo says, ‘and why I thought even to say numbers obviously exist is to take the question too seriously, but to tell you the truth, I can’t remember what my answer was’.
Understanding the quizzicalist project in these terms – as an effort, in the first instance, to make sense of linguistic practice through a more realistic theory of meaning – also reveals a connection between the papers in Things (which are mostly about the world) and those in Thoughts (which are mostly about the mind). There’s stuff in Thoughts about mental causation and properties, but most of the collection concerns the mind-body problem, which comes, in contemporary philosophy, to the question: what sort of relation does the mind bear to the physical world? Descartes’ dualism – that mind and body are different sorts of substances – is more or less out the window, but the broadly physicalist view of the world that many of us find natural is still threatened by two intuitions