The metaphysics wars

by Massimo Pigliucci

 I am not a metaphysician (or a metaphysicist, as some call themselves), but I've been fascinated for a while by what I've come to think of as the metaphysics wars. Let me explain. Metaphysics is, of course, one of the classic branches of philosophy, tracing back at least to the pre-Socratic Thales of Miletus (the guy who thought that all is made of water), and of course getting its name from Aristotle's treatise (though that wasn't the original title, it was named so afterwards, because it came after Aristotle's Physics).

Metaphysics was very important to the ancient Greeks, and absolutely crucial to Medieval philosophers. Though, beginning with David Hume, it took a bit of a nosedive in terms of its reputation, even among philosophers. Hume, of course, proposed his famous "fork," a test to figure out whether a book was worth your time:

If we take in our hand any volume; of divinity or school metaphysics, for instance; let us ask, Does it contain any abstract reasoning concerning quantity or number? No. Does it contain any experimental reasoning concerning matter of fact and existence? No. Commit it then to the flames: for it can contain nothing but sophistry and illusion. (An Enquiry Concerning Human Understanding)

Needless to say, books on metaphysics failed the test, according to Hume. Closer in time to the present, the early 20th century logical positivists thought that metaphysical notions were not even wrong, indeed, they were literally nonsense, since they failed another famous test of their devising, known as the "verification principle" (if there is no way to empirically verify notion X, then notion X is incoherent - notoriously, the problem was that the verification principle itself cannot be verified empirically...).

Ever since the second part of the 20th century, though, metaphysicians have tried again to get their house in order, striving anew for logical rigor. Which brings us to the current "wars."

If you want to have an idea of just how split philosophers currently are about metaphysics, you need not go any further than two recent (voluminous, highly technical) collections of essays. The first, edited by David Chalmers (he of philosophical zombies, and more recently of Singularity memory), David Manley and Ryan Wasserman, about "meta-metaphysics" (but, really, about metaphysics). The second one, edited by Don Ross, James Ladyman, and Harold Kincaid, about "scientific" (also known as "naturalized") metaphysics. The two volumes couldn't have less in common (indeed, they cite largely parallel literatures), and couldn't present more of a stark contrast between two completely different ways of thinking about (and doing) metaphysics.

So, what's all the fuss about? Before going on, I must admit to finding Ross' and colleagues' argument a bit more compelling, and of course, as some of my readers know, I have come to pretty much distrust much of what Chalmers has to say, about anything. Still, I do think that there is a middle way (or perhaps a 2/3 of a way), perhaps along lines sketched by Cian Dorr in a review of a previous book by Ladyman and Ross.

The basic thrust of the meta-metaphysical approach (which I will less pretentiously and more accurately call "classical metaphysics") is that there is nothing wrong in principle with metaphysics the way it has been practiced since Thales, and that what needs to be done is to sharpen one's logical tools even further, clean up the house from outdated notions, and keep adding new, more sound ones. From this perspective metaphysics is entirely independent of science, for the simple reason that it is concerned with problems - and it deploys tools - that are quite distinct from those of science. My attitude toward this approach is ambivalent: on the one hand, I want to say "good for the metaphysicians!," stand your ground and forge your own path. On the other hand, I get irritated by some metaphysical papers that very quickly veer toward what Ladyman and Ross (perhaps a bit uncharitably) call "neo-Scholasticism." To put it as they do in the first chapter of their Every Thing Must Go manifesto: [this way of doing metaphysics] "contributes nothing to human knowledge," its practitioners are "wasting their talents," and the whole thing, although "engaged in by some extremely intelligent and morally serious people, fails to qualify as part of the enlightened pursuit of objective truth, and should be discontinued." Ouch.

So what do Ross and co. propose instead? They think that metaphysics ought to abandon the goal of figuring out the basic ontological structure of the universe, because this is now the province of science, especially fundamental physics. The metaphysicist, instead, should set as her goal to do what scientists themselves are too specialized to accomplish: to make unified, cross-disciplinary sense of what the special sciences (i.e., everything but fundamental physics) and fundamental physics together tell us about how the universe is structured. To put it simply: there ain't gonna be any metaphysics without taking on board science, a lot of science. They go on (in the above mentioned Every Thing Must Go) to develop the beginning of such a picture, something called Ontic Structural Realism, the details of which need not concern us here.

If you have great sympathy for the scientific enterprise (as I do, as a scientist), then you'll like the idea of naturalized metaphysics. If you are weary of the scientistic (a word Ladyman and Ross use with pride) excesses of some science authors (as I am, as a philosopher), then you'll want to at least temper the enthusiasm for naturalized metaphysics, while at the same time trying not to fall back into neo-Scholasticism.

And it is precisely this middle, or whatever, ground that no one so far has been able to stake out very clearly. Except perhaps for a review of Ladyman and Ross's Every Thing Must Go, published in the Notre Dame Philosophical Reviews (link above) by the above mentioned Cian Dorr (thanks to our guest blogger, Michael Lopresto for bringing it to my attention).

Dorr acknowledges the bite of Ladyman and Ross's critique of classical metaphysics, but then attempts to stem the tide of naturalistic metaphysics in what I think are interesting ways that ought to be taken seriously.

To begin with, for instance, Dorr takes up a standard criticism of classical metaphysics (and, indeed, of much of analytic philosophy): its (alleged) reliance on intuitions. In the past several years even so-called experimental philosophers have gotten into this particular fray, with empirical studies purporting to show that what many analytical philosophers consider intuitive notions are not actually shared by common folks (but, really, who cares? Do physicists care that common folks don't share their notions of how the world works?), or by people from other cultures (again, many Chinese doctors don't share the Western skepticism of their traditional medicine, but too bad for Chinese doctors - and their patients!).

Dorr, however, doesn't take the predictable route of defending the intuitions shared by Western metaphysicians. He takes the more radical - and, in my opinion, more accurate - step of denying that much analytic philosophy actually depends on intuitions to test its own notions.

He begins by acknowledging that in (classical) metaphysics one is in the business of producing logical arguments. These are based on a number of premises, which are then logically connected in a manner that yields certain conclusions. It has been that way since at least Aristotle, who codified this way of doing things in philosophy.

Now, as it is well known to students of Logic 101, there are two characteristics of logical arguments, pointing to the two major ways in which one can mount counter-arguments: a given argument may be valid and/or sound (or neither). Validity refers to the logical structure of the argument: if the structure is such that, given the premises, the conclusions do logically follow, then the argument is valid. Soundness is concerned with the premises: are they, in fact, true (or at the least justifiable)? One can produce an argument that is valid, and yet founded on wrong premises (unsound); or one can have an argument that starts out with good premises, but reaches its conclusions in a way that is logically unwarranted (it's invalid); or - ideally - the argument can be both valid and sound. (The fourth possibility, that both the premises and the logical structure of the argument are bad is presumably rarely encountered among people whose profession is to argue logically, but you never know.)

Now, even Ladyman and Ross admit that much of the published classical metaphysical literature is done by professionals who can recognize an invalid argument (and if they can't, their peers will gleefully point it out to them at conferences or as soon as the paper is published). But what about the premises? As Dorr drily puts it, they don't come out of some hidden "premise factory." Whence then? Here is where the much maligned intuitions come in, since often (classical) metaphysicians (and more broadly analytic philosophers) find themselves saying things like "it is intuitive that..." or "it is counter-intuitive that..." Aha! But intuitions aren't the equivalent of scientific data, as Ladyman and Ross rightly say. Indeed, what makes classical metaphysicians think that our faculty of intuition - which presumably evolved in the prehistoric times of our species - is reliable about anything other than mere survival (and reproduction)?

Let us set aside for a moment that if Ladyman and Ross's criticism were taken just a tiny bit further we would have a really hard time explaining how, say, intuitions about quantum mechanics, not to mention mathematics, are possible also (neither has to do even remotely with survival and reproduction). Instead, Dorr's rebuttal is much more mundane, though just as devastating. I will leave him the floor for a minute:

[Ladyman and Ross's] is an understandable worry, and one that metaphysicians have invited in their attempts to reflect on their own methodology. These reflections make it look like 'appeals to intuition' are part of a distinctive method for doing metaphysics, a method we could contemplate giving up in its entirety, as the authors indeed advocate: 'as naturalists, we are not concerned with preserving intuitions at all.' But very often, 'intuition' talk is playing no such distinctive role. Often, saying 'Intuitively, P' is no more than a device for committing oneself to P while signaling that one is not going to provide any further arguments for this claim. In this use, 'intuitively … ' is more or less interchangeable with 'it seems to me that … ' There is a pure and chilly way of writing philosophy in which premises and conclusions are baldly asserted. But it's hard to write like this without seeming to bully one's readers; one can make things a bit gentler and more human by occasionally inserting qualifiers like 'it seems that.' It would be absurd to accuse someone who frequently gave in to this stylistic temptation of following a bankrupt methodology that presupposes the erroneous claim that things generally are as they seem. But the sprinkling of 'intuitively's and 'counterintuitive's around a typical paper in metaphysics is in most cases not significantly different from this. It may be bad style, but it is not bad methodology, or any methodology at all, unless arguing from premises to conclusions counts as a methodology.

Here is another way to put it, which is consistent with my own experience in doing philosophy. When an analytic philosopher says that "it is intuitive that..." she is simply putting out in the open the (unargued for) premises of her reasoning. There is nothing wrong with unargued premises: mathematicians do it all the time (they call them axioms), and you can dig them out also of scientific papers (which, after all, don't start every time by defending the entire edifice of knowledge accumulated up to that moment). The point is that such premises are out in the open for everyone to see - and therefore potentially to be argued against. And that's precisely how analytic philosophy works: your colleagues will either challenge the logical paths through which you have arrived at your conclusions (i.e., the validity of your argument) or the premises from which you started (i.e., the soundness of your argument), or, of course, both.

So when classical metaphysicians appeal to "intuition" they don't (or, at least, ought not) refer to some magical ability only they possess. Rather, they are simply using rhetorical language (of which there are many other examples in philosophy: "surely..." "it is obvious that...") while parading their starting points in plain view. As Dorr puts it, it's nonsense to dismiss the entire enterprise by quibbling on matters of style.

But there is at least another major bone of contention between naturalistic and classical metaphysicians, and that's the issue of what metaphysics is for.

Here it is clear that Ladyman and co. do have at least a partial point: part of the original scope of metaphysics was to investigate the physical structure of reality. Thales thought it was all water, for Heraclitus it was all about fire, etc. That sort of enterprise has, in fact, been delegated to fundamental physics. It is the latter that is going to tell us whether the stuff of reality is made of quarks, strings, or - according to ontic structural realism - of mathematical relations (yeah, chew on that one for a while). But this is nothing new in the history of philosophy: science itself used to be natural philosophy, but it is now a panoply of independent disciplines. Does that mean that philosophy has therefore inched itself closer to being out of business? Not at all, witness the spectacular flourishing of philosophy of science (and of biology, of physics, etc.) during the past century or so.

In this sense, Ladyman and others' project of turning metaphysics into an interdisciplinary, cross-sciences field, makes perfect sense. But there is another project for metaphysics, that is not "scientific" in nature, and yet appears to me to be perfectly valid: to make sense of the logical structure of the world. (If you think the world doesn't have one, then pray explain to me how you think we can make sense of it.)

Here are some examples of this kind of metaphysics, again from Dorr's review:

What is puzzling about [Ladyman and Ross's rejection of classical metaphysics] is that it instructs us to ignore a very large class of arguments without telling us anything at all about where they fail. Consider a simple metaphysical argument that refers to no scientific hypotheses: 'the statue on my desk was made this morning; the lump of clay on my desk has existed for a long time; so the statue on my desk is distinct from the lump of clay on my desk; so distinct material objects sometimes spatially coincide.' Or an argument that appeals to only one scientific hypothesis [Ladyman and Ross require at least two, since scientific metaphysics is about building bridges between sciences]: 'If presentism is true, simultaneity is absolute; but simultaneity is not absolute [because of relativity]; so presentism is not true.'

Now, admittedly spending your time thinking about lumps of clay or the issue of presentism may not be your cup of tea. In which case I would advise against a career in (classical) metaphysics. Then again for most people, thinking about 13-dimensional universes also isn't their cup of tea, and yet we don't relegate the (so far, possibly perennially) empirically untestable string theory to the heap of neo-Scholasticism. As Dorr says, it's hard to see why this sort of metaphysics doesn't contribute to the store of human knowledge, at least in the same sense as modal logic or Fermat's Last Theorem do (i.e., as interesting - to some - intellectual puzzles that may or may not someday have some practical application, but that's not why we engage them).

All in all, it seems to me that when metaphysicians of the type that contributed to Chalmers et al.'s volume reject outright scientific input as irrelevant to what they do they are mistaken, or at the least they do so at their own peril. But Ross and co-authors seem to make precisely the opposite mistake by not leaving any space at all to metaphysics except as a highly constrained handmaiden to science. Both projects (and some hybrids too!) are worthwhile, so long as all interested parties use logic and (relevant) evidence properly while refraining from unproductively insulting their colleagues across the isle.