Rationalism And Science

I've been thinking a bit about rationalism, empiricism and science, and I tried writing some notes to organize my thoughts about it. It's all pretty half-baked and unsatisfactory, but I've turned it in into something I can put here anyway, in case it's the kind of thing anyone likes to read.

Rationalism vs Empiricism

• Roughly: empiricists think knowledge only comes from experience, while rationalists think pure reason has an important role.
• Rationalists tend to think experience has some role too, although they might think that the kind of knowledge that involves experience isn't so good, or perhaps isn't knowledge strictly speaking at all.
• Empiricists sometimes think it's OK to get mathematical and/or logical knowledge from pure reason. Maybe you can get some knowledge of analytic truths that way too, although under the influence of Quine (and Morton White, usually via Quine) they might not think there are any properly analytic truths.
• If you want to firm up this second source of knowledge as part of your position, you can appeal to Hume's Fork. Hume's Fork is the idea summed up in this quote from the end of his Enquiry Concerning Human Understanding (emphasis in original):

  "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."

  It takes some interpreting to get this passage to be arguing for exactly the empiricism-plus-maths-and-logic position, but it's in the ballpark. If you do adopt this package, you might even be able to get away with calling yourself a logical empiricist, like Rudolf Carnap. Carnap is very in at the moment, and is also generally considered to have been a great guy.

Descartes And Leibniz

• They were scientists and mathematicians, but they were also metaphysicians.
• As philosophers, we tend to look more at their metaphysics than their science, unless we're specialists. The science is more obsolete than the metaphysics (although perhaps not more wrong), science isn't really taught via 300-year-old texts even when it isn't obsolete, and we're not studying science anyway. And we're probably even less interested in reading their maths than in reading their science.

The Appeal Of Empiricism

• When you're reading their metaphysics, sometimes they will invoke principles of pure reason to derive their metaphysical conclusions. For example, Leibniz invokes such useful gizmos as the Principle of Sufficient Reason and the Identity of Indiscernibles. Descartes says things like there must be at least as much reality in an efficient and total cause as in the effect of that cause (from Desmond M Clarke's 1998/2000 translation of Descartes' third Meditation). And Spinoza, the other member of the Big Three rationalists, takes this kind of thing to a whole new level with an axiomatic presentation of his grand metaphysical system in the Ethics. You have to wonder what justifies their principles, and sometimes it can seem like they're just making up premises on the fly to get themselves out of an argumentative tight spot. I suppose this is particularly the case with Descartes, who makes things even worse by appealing to the light of nature, or the natural light of reason, and we often read Descartes when we're young and impressionable. Perhaps harping on about the natural light of reason makes a good impression on some young philosophy students, but it didn't make a good impression on me.
• The metaphysical conclusions that they derive aren't even especially attractive to a lot of us. The existence of God, the non-physical soul, pre-established harmony and so on. We feel like we could easily get by without them, and then we wouldn't have to accept the premises, or the embarrassing Light Of Nature methodology by which they arrived at them.
• Science, on the other hand, is an empirical discipline. We're quite sure of that. So while we might not know exactly what goes on across campus in the science departments, we don't really worry that anything of importance will be lost to science if we become empiricists. So we can keep science much as it is, while taking a suitably unenthusiastic attitude towards metaphysics, saying that metaphysical theses are either unknowable, or probably wrong, or Not Even Wrong.
• We can still do a little bit of metaphysics, criticizing theses for conflicting with our best science, or for being internally incoherent. And we can also sometimes have a go at offering an empiricist critique of some of the things scientists get up to, when we take them to be straying into metaphysics. The interpretation of quantum mechanics is a good source of material there, although it is often difficult for philosophers to understand the relevant science well enough to get taken seriously. (And even if they do understand the science, getting taken seriously still isn't a given.)

Pure Reason In Science?

• All this seems like a very nice package, but there's a fly in the ointment, which is that scientific methodology may actually include an awful lot of rationalism. Sure, it's an empirical discipline, in that scientists gather data and do experiments and so on. But they also spend a lot of time filling whiteboards with equations, and they're even known to have flashes of inspiration in the shower, as if their problem has been suddenly illuminated by the light of nature. (Archimedes' alleged eureka moment in the bathtub is not a good example of this, since his flash of inspiration was about his displacement principle, and one has experiences relevant to that in a bathtub. But it does happen to scientists working on things besides bathtubs too.)
• Empiricists do have resources to push back on this line of thought. They're still allowed to use pure reason for maths, and for logical inferences. Perhaps that's what's going on with the whiteboards and the flashes of inspiration, and so under closer examination it will turn out that scientists aren't doing anything outside the empiricist's rules.
• Now, the closer examination of actual scientific practice is something that has been done an awful lot by other people, under the auspices of history and/or philosophy of science. I blush to confess that I do not have much familiarity with any of this literature. If you do, then please do correct me if I'm wrong, because I'm going to make a naive pessimistic case that under closer examination what we'll find is that science is in fact a bit of a Cartesian free-for-all.

The Problems Of Induction

• Induction, roughly, is when you take some observations, find a general rule that fits the observations, and then apply that rule to make predictions about new observations. If it didn't work, then it'd be hard to see how science could work. But there are two reasons why it is hard to see how induction could possibly work.
• The classic problem of induction is the problem of justifying the idea that old patterns can be expected to persist at all. We set up the dilemma as follows. (It'll be based on AJ Ayer's presentation of the problem in chapter two of Language, Truth and Logic, although Ayer himself thinks the problem's very hopelessness makes it a pseudo-problem as traditionally conceived.) Either inductive reasoning is justified deductively or inductively. An inductive justification would point to how old patterns have persisted after being identified before, and this is itself a pattern we can expect to persist into the future. But this reasoning seems circular. The deductive justification is in bad shape too, on the grounds that there just isn't any logical inconsistency in patterns being broken. A coin landing heads twenty times in a row is consistent with its landing heads the twenty-first time, as an inductive reasoner would presumably predict, but it's also consistent with its landing tails the twenty-first time, providing a counterexample to any attempted deductive justification of induction.
• The new riddle of induction, which we have Nelson Goodman to thank for, is still a problem even if you can solve the classic problem of induction. This time the problem is no longer showing that patterns will persist, but deciding which patterns we should expect to persist. There are lots of patterns consistent with any dataset, and we will get different predictions depending on which patterns we identify. Of course, there are some patterns that humans identify more readily than others. But justifying this as anything more than a cognitive bias, while still working within the empiricist's rules, is difficult.
• Rationalists, as we've learned, can appeal to the light of nature to get themselves out of just this kind of tight spot. Can't justify induction inductively or deductively? Just appeal to the light of nature! Not sure which pattern is more likely to persist? Let the light of nature show you the way.
• This is of course a bit flippant. Rationalists do have resources to invoke premises when an empiricist would be in a tight spot, but they can't do this arbitrarily, at least not by their own lights. Are the resources you need to deal with induction the kind of resources rationalists would appeal to?
• I think they are, or could well be. To get a handle on why, consider Plato's theory of forms. One of the problems the forms are supposed to solve is how we can have knowledge of general things, even though we only experience particular things. Plato's idea is that knowledge of general things is knowledge of transcendent forms, which are somehow reflected in the particular things, and which we apprehend with the intellect rather than with the senses. Mathematical knowledge is knowledge of forms, but scientific knowledge is knowledge of forms too. Aristotle didn't think that forms were transcendent, but (as I understand it) he still thought that scientific knowledge was knowledge about forms, or essences if that's different, and that in any case these are apprehended by the intellect. The exact mechanism by which the intellect apprehends the forms is hard to pin down - Plato suggested we remember them from directly experiencing them before we were born - but the idea of scientific knowledge being knowledge of something general apprehended by the intellect has had real staying power, and is the kind of thing rationalists in particular are into.
• This gives rationalists a bit of purchase on the problems of induction. For the classic problem, the idea is that we can learn something about events before we observe them, because the same forms show up in those events as the ones we have already observed. For the new riddle, the idea is usually that not all rules are equal because some correspond simply to forms, and some don't. Not every gerrymandered property you might think of corresponds to a form, and the ones that don't aren't as likely to fit in robust generalizations.
• You can try to rerun the arguments against the rationalist if you like. How do we know that forms will carry on behaving the same way we're used to? How do we know which properties correspond to forms? Well, because we examine them with our intellects and discover which forms there are and that they behave uniformly. How do we pull that off? Good question! But it seems we do pull it off, since science works. Denying that it could possibly work flies in the face of the evidence, and denying that it could work this way risks begging the question against the rationalist.
• So, we've got an argument that science has a problem that rationalists have the resources to solve and empiricists don't. For that, we didn't need to look at the actual practice of science at all. But now things get a little trickier. I'm going to make two suggestions, neither of which I have the expertise to properly back up.
  • First, a large part of what Descartes and Leibniz liked about being rationalists was that it gave them the resources as scientists to respond to just this kind of problem.
  • Second, not much has changed. Scientists are still leaning heavily on roughly the same rationalist methodology that Descartes was into, and being wildly successful with it too.

How Descartes And Leibniz Did Science

• In the seventeenth century it was possible to feel really good about the prospects for science. The progress they were making made understandable a level of optimism that may only have been equalled before or since by physicists in the late 1920s. They really felt like they would soon have it all figured out, and that when they did the answers would be simple, beautiful, and powerful.
• Descartes and Leibniz also took it more or less as a methodological axiom that the world was nicely ordered along principles that could be understood and discovered by humans. This is an idea that goes back at least to Plato's Timaeus, and on some accounts goes all the way back to Thales and is what sets philosophers like him apart from the storytellers like Homer and Hesiod who came before him. The Stoics were big on the idea, it persisted in some form throughout the middle ages, and in the seventeenth century it was as popular as ever. It's an appealing idea, and people working with the idea keep making discoveries and building cool stuff, while sceptics just bring everybody down. When asked to justify this methodological axiom, neither Descartes nor Leibniz was above talking about God. Both of them thought that God in his goodness had given us rational faculties which when used properly would be able to get us significant scientific knowledge of the world. Leibniz in particular also thought that God's perfection meant that he would make the world excellent - the best of all possible worlds, as they say - and that we could work out what would count as excellent, and use this to guide our theorizing both in science and metaphysics.
• So, how do you do science with this attitude? Well, prompted by observations and guided by the light of nature, you come up with a beautiful, simple, powerful theory of how the world works. You make the theory nice and mathematical, and maybe come up with some new maths like calculus (Leibniz) or co-ordinate geometry (Descartes) especially for the purpose. You do experiments to test the theory. If the predictions are borne out, great! If not, maybe there's something wrong with the experiments. Or maybe there's something wrong with the theory. Eventually you come up with something nice that fits the results you're getting. And because the world does in fact conform at least approximately to the kind of principles that seem simple and beautiful to seventeenth-century optimists, the whole thing went swimmingly.

How We Do Science Now

• Basically what I want to say is that we do things much the same way. We might not think that's what we're doing, but it is. More or less.
• When scientists are explaining how science progresses now, they'll sometimes offer an account based on Karl Popper's ideas. I haven't read Popper, and I expect the scientists often haven't either, because the account isn't really very plausible and it'd be uncharitable to attribute it to Popper himself. Here's how it goes. Scientists look at the data they're already aware of, and they come up with a theory that fits. The important thing about the theory is that it be falsifiable, in that there are experiments they could do or observations they could make that would show that the theory was false. Then they do experiments and/or make observations. If the results are what the theory predicts, the theory is more likely to be true. If the results aren't what the theory predicts, the theory is false and so they go back to the drawing board.
• When pressed, people usually admit that this does not really reflect scientists' actual responses to data not fitting their theories. There might be something wrong with the experiment, or maybe the theory does predict it after all but there was something in the initial conditions you weren't aware of. A classic example is the orbit of Uranus: it didn't fit with the predictions people made for it using Newtonian mechanics and gravity, but that's just because they didn't know Neptune existed. Include the gravitational effects of Neptune and Newtonian mechanics and gravity aren't falsified after all. That's how Neptune was discovered, or so I'm told. (The hero of that story is Urbain Le Verrier.) They tried to pull the same trick with a planet inside Mercury, which they called Vulcan, but there it turned out Newtonian mechanics and gravity really were the problem, and Einstein's theory of gravity explains it much better. But there was a long time in between unsuccessfully looking for Vulcan and rejecting Newtonian gravity.
• OK, so let's put aside naive falsificationism. How does science work, then? Well, I'd suggest they do pretty much what Descartes did. You have a sense of the kind of data you're trying to fit your theory into, and then you make something up that you're happy with, guided by the light of nature. Your theory will have some blanks in it like the mass of the electron or whatever, and when you find some way of taking measurements to fill in the blanks, you do. Then you cling on to the theory like grim death in the face of both friendly and unfriendly data until finally you come up with something you're not quite as unhappy with. This account adopts some themes people tell you come up in Kuhn and Lakatos - I haven't read them either - and what it agrees with Popper about is that the whole process works much more smoothly if your theory is the kind of thing that data can be friendly or unfriendly to. (That's why it doesn't work so well for metaphysics, I suppose.)
• The account is a total caricature, of course. But I'm hoping it's a caricature of the actual practice of science, unlike naive falsificationism, which is a caricature of what some scientists imagine they must be doing because rationalism somehow doesn't seem hard-nosed enough. Now, while it might sound like I'm being a bit mean to scientists, that's not my intention. If the rationalists are right, then this could be exactly what scientists ought to be doing. And whatever they're doing, they seem to be doing it very well.

The Moral Of The Story

• Sometimes people give the rationalists a hard time. We do sort of acknowledge that Descartes, Spinoza and Leibniz were great philosophers - I mean, everyone says so, right? - but when we look at their philosophical systems what we see are bad arguments for false conclusions. It's all too easy to attribute this to a bad methodology, saying that the problem is that they were rationalists. Maybe we should ditch the light of nature, stick with empirical methods plus maths and logic, embrace science and be quietist about metaphysics.
• What I'm suggesting is that this line of thought has a great big hole in it, which we don't notice because we don't think of the rationalists as scientists. Or perhaps we do think of them as scientists, but don't think of that as relevant to their philosophy. But it is relevant. They were scientists, they were good at it, they did science as rationalists, and we're still doing that today. If you want to assess rationalism at its best, then don't consider it as a method in metaphysics; consider it as a method in science. That's the moral of the story. The question is, is it a true story?

What's Wrong With This Picture?

• I mentioned earlier that there's a lot of stuff here that I'm pretty ill-informed about. Maybe you thought I was being disingenuous, but I wasn't. There's a lot to learn here, and I haven't learned it. And if you have, you probably don't need me to tell you that. The evidence is right there on the page.
• Nonetheless, this is where I am at the moment with this stuff. From where I'm sitting, it looks like you can't really get anywhere in science as an empiricist, the actual practice of science bears this out, and the rationalists should be given a bit more credit for it. So, what might I be wrong about?
• First, I might be wrong about empiricism's platform. Maybe they've got some clever solutions to the issues with induction that I was worrying about. Or maybe they're willing to embrace a greater level of scepticism than I appreciate.
• Second, I might have Descartes and Leibniz wrong. I've read a fair bit of both, but there's an enormous amount left that I haven't read, and I do find the scientific practice they envisage all a bit mysterious. That's why I describe it in these scathing terms, before insisting that what I described is the tried and tested scientific method that built the modern world. I think we should have a fairly low prior that a method that sounds like that could build a world that looks like this.
• Third, I might have modern science wrong. Who knows what these people get up to? They don't even seem to know. But those historians and philosophers of science I mentioned before probably have some idea, and I could try checking some of that out. I could at least read Kuhn. Everyone reads Kuhn.
• Fourth, I might be wrong about something else. I don't know what. But the whole situation is very unsatisfactory, and I think I must be missing something.

Reading List

• So, I've got some reading to do! If you've got this far and you think I'm a doofus who should calm down and read X and then everything will become clear, then please point me towards X in the comments. In the meantime, here are some things I could look at.
• The logical positivists/empiricists in the first half of the twentieth century were often pretty clued up about science, but they were also pretty thoughtful and self-aware about their empiricism. So perhaps I should read some Schlick or something.
• I found a book in a second hand shop the other day by Daniel Garber called Descartes' Metaphysical Physics. I probably won't read it all, because I am a non-serious person, but it looks relevant and I'll probably read some of it.
• I could have a look at some of Descartes and Leibniz's more scientific stuff, and see how they talk about what they're doing.
• I've only got a pretty sketchy understanding of Plato and Aristotle's understanding of form and how it helps with epistemology, so I should probably read something about that.
• Like I say, I could read Kuhn, at least The Structure of Scientific Revolutions. I should probably read something by Lakatos too. Popper is less of a priority.
• I saw an NDPR review of a book called Platonism at the Origins of Modernity: Studies on Platonism and Early Modern Philosophy, and it looked like some of the papers in that would be relevant.
• Once I've got through that lot I'll probably be down multiple rabbit-holes, so for me to put anything else on the list now would probably be a bad idea. But if you can point me to anything that would sort all this out for me, I'm all ears.

Gambling With The Metaphysics Oracle

A Tax On Bullshit

There's a lot of bullshit around. Wherever you look, people are confidently making predictions, often while being paid to so, and by the time we've been able to test these predictions the people who made them are long gone, sunning themselves on a beach somewhere, spending our money and laughing at us. It's a sorry state of affairs. What can we do about it?

One idea, and it's a good one, is to get people to put their money where their mouths are. Offer people bets on their predictions. If they really believe what they're saying, they shouldn't mind having a little bet on it. If they don't believe it and bet anyway, then at least their bullshit is costing them something. People sometimes call betting on predictions a "tax on bullshit". The person I've heard talking most enthusiastically about this idea is Julia Galef, who I suppose is a pillar of what people refer to as the Rationality Community. Apparently she does it in her everyday life. She's always sounded to me as if she has a fun life, but I think I'm probably too much of an epistemic pessimist to fit in well with the Rationality Community myself.

Regular readers may recall that I sometimes worry about bullshit in philosophy. A lot of the claims philosophers make aren't really very testable at all, and so you can keep up your bullshit for thousands of years without ever being found out. Of course, if something isn't testable then it's not practical to bet on it. But lately I've been wondering how philosophers, particularly metaphysicians, would react if we somehow could offer them bets on their claims. Peter van Inwagen (1990), for example, doesn't think tables exist. When we think we're in the presence of a table, he thinks we're really just in the presence of some simples arranged tablewise. But if we could go to an Oracle to settle the question, would he put his simples arranged moneywise where his simples arranged mouthwise are?

Taking The Bet

The simplest response is for the philosopher to just take the bet, and offer us very favourable odds corresponding to how very sure they are that they're right. Maybe the methods we use for answering metaphysical questions aren't so different in principle from the methods we use for answering any other kind of question, and if we've got what we take to be a good argument then we should be confident in its conclusion. I think that plenty of metaphysicians would have no problem at all taking these bets. They mean what they say quite literally and they are confident that their answers are right.

Declining The Bet

A second response is not to take the bet, on the grounds that you don't actually believe the metaphysical positions you've taken. There are at least two ways this could work, one obvious and disreputable and the other less obvious and more respectable. The obvious one is that you're not actually committed to these positions the way you said you were. You were bullshitting, perhaps without properly realizing it, and now you've been found out. The more respectable one is that you are committed to your metaphysical positions, but the mode of commitment you take to be appropriate to metaphysical positions is not belief. It's something else. Helen Beebee (2018) argues for something along these lines, building on Bas van Fraassen's work on the analogous question in the philosophy of science. For Beebee it's largely a response to the phenomenon of expert disagreement in philosophy and concern about the reliability of philosophical methods, while for van Fraassen I understand it's more about the underdetermination of scientific theories by evidence¹. For Beebee and van Fraassen, this kind of commitment is less about believing the untestable parts of the theory and more about committing oneself to participating in a particular research programme.

Rejecting The Setup

A third response is to reject the bet on the grounds that you reject the authority of the Oracle. How can you reject the authority of an Oracle? The basic idea is that we can't imagine anything the Oracle could say or do to convince us that our position is wrong, but you have to be careful with this sort of dialectical move. You don't want to be the sort of person who responds to the trolley problem² (Foot 1967) by saying they'd dive off the trolley and push the workers out of the way, or some other such silliness. This kind of move usually just serves to derail the conversation and prevent us from engaging with the point the thought experiment was trying to make. In the trolley problem you just stipulate that the situation is simple and the outcomes given each action are certain.³ In the Oracle thought experiment you similarly stipulate that the Oracle is reliable (or infallible) and trusted by all parties. Nonetheless, I think that sometimes it does tell us something useful if we push back on the setup.

The cleaned up certain-outcomes version of the trolley problem isn't very realistic, but it's still something we can imagine. With at least some metaphysical questions, however, the Oracle thought experiment might give rise to what philosophers call imaginative resistance. This is what happens when what you're being asked to imagine somehow doesn't make sense to you, to the point that you struggle to imagine it. It can happen in various ways, including when a story is blatantly inconsistent, or when the moral facts in a story as stipulated conflict with the moral judgements we're inclined to make ourselves when given the non-moral facts. I want to suggest that this imaginative resistance is an indication that even if we take for granted that the Oracle is reliable and that we trust it, this might not be enough. We might still disagree with it, for reasons other than our not trusting it.

I can think of a couple of kinds of case where this situation might arise. Both embody a kind of Carnapian attitude towards philosophical questions. First, suppose we're asking the Oracle about whether there are tables, and it says that there are. Van Inwagen could respond in a couple of ways:

• "Fair enough; that's a weird and oddly cluttered world, and there was no way for me to find out that there were tables, but I guess you're the Oracle here."
• "Look, if you want to describe the world as having tables in it, that's up to you. I'm going to keep describing it as not having tables. We're both right by the lights of our own description schemes, and choosing between the schemes is a practical matter about which you're not the boss of me."⁴

Second, suppose that we're asking the Oracle what the correct analysis of knowledge is, and it says the correct one is Robert Nozick's (1981) counterfactual truth-tracking analysis. We point out all the bizarre results this commits us to as outlined by Saul Kripke (2011), and the Oracle just shrugs, says that's what the word "know" means, and presents a bunch of linguistic usage data to back up its claim. Again, two responses:

• "Fair enough; the word 'know' isn't as useful as we thought it was, and we can be forgiven for thinking Nozick was wrong, but it means what it means and we must accept that."
• "Look, if that's what the word means, then the word isn't fit for purpose. We need a concept of knowledge we can use for talking about important issues about humans' access to information about the world, and the concept embodied by this linguistic usage data simply can't be used for that."

These two cases are quite similar. The difference is that in the tables case the philosopher says they weren't wrong about anything: the Oracle and the philosopher have just made different choices, and they are the authorities over their own choices. In the knowledge case the philosopher is shown to be wrong about who knows what, but they push back by saying this just means we need different concepts. The cases kind of shade into each other a bit, but I think the distinction is there, and that the knowledge and tables cases are on different sides of it. Van Inwagen would not be surprised to be shown that we talk as if there are tables. Kripke would be surprised to be shown that we talk as if Nozick's is the correct analysis of the concept expressed by the word "know". That's a difference.

Now, even if you take one of these Carnapian lines, the Oracle could still push back and say that actually you're wrong about whose concepts are better. It might not want to do that in the knowledge case; it might agree that our word "know" attaches to a concept that isn't very useful. But the point is that the Oracle knows everything there is to know, and so it might know something that would make you change your mind. The thought here is along the lines of what Carrie Jenkins (2014) argues for and calls Quinapianism: the decisions over which concepts to use to describe the world are up to us the way Carnap thinks, but our views about which concepts are best are revisable in the light of new information the way Quine thinks all our cognitive commitments are. But even if the Oracle's omniscience gives it an advantage over us, what we end up with here is still a philosophical discussion of the more familiar kind. The Oracle makes the case for its recommended set of concepts, but it's still up to us which concepts we end up using.

So What?

I've had a bit of fun thinking about this, but does it tell us anything about anything? I think it does. I'm inclined to take philosophical questions at face value, and to have the same commitments with respect to them inside and outside of the philosophy room. If I'm bullshitting, I'm not consciously or deliberately bullshitting. I've got a lot of philosophical commitments, albeit subject to a great deal of uncertainty, and I'm sincere about them. But I think my responses to this thought experiment vary a lot depending on which philosophical question we're talking about. Sometimes I think I'd take the bet. Sometimes considering being offered a bet makes me feel more uncertain. (I guess in these cases either I'm being called on my bullshit or the feeling of added uncertainty is itself unjustified. Perhaps it's rooted in risk aversion.) And sometimes I come over a bit Carnapian and get one or other kind of imaginative resistance. (I'm not sure I ever feel the way Beebee suggests I should feel, but I don't understand her position terribly well, and in any case I've only run the thought experiment on a few questions.)

This variation is interesting to me. When people are talking about the status of philosophical propositions and beliefs, they sometimes make it sound like they think we should go for the same response to everything, or perhaps one response for ethics and another for everything else. But I feel very torn between the different responses for a lot of questions, and I lean quite different ways for different questions even within the same branch of philosophy. So when Beebee, Carnap and the rest are putting forward views on the status of philosophical disputes, an answer that works well for one dispute may not work so well for another. One more thing to worry about, I guess.

Notes

[1] There is a connection here, in that van Fraassen is sceptical about the reliability of scientific methods to verify the parts of theories that go beyond their empirical adequacy, for example by positing unobservable entities. I'm not a good source for van Fraassen though: most of this is coming from Beebee's account of his position.

[2] The trolley problem is a thought experiment where someone driving a train (or trolley) is going to hit five workers on the tracks, and the only way to avoid killing them is to steer down a side track and kill another, different worker. The original puzzle is explaining why the driver ought to steer and kill one to save five, even though in some other situations it's better to do nothing and let five people die than to act to save them at the cost of killing someone else. Foot gave the example of framing someone to prevent a riot, and another common one is killing someone to use their organs, which I think is due to Judith Jarvis Thomson (1985). Since Thomson's paper there has been a large research programme involving variants on the trolley problem. Some people think it is silly and dismissively call it 'trolleyology'. My own view is that it's unfairly maligned, although I do quite like the word 'trolleyology'.

[3] Foot does acknowledge that the trolley case isn't especially realistic and that the worker might be able to get out of the way. But she also notes that the relevant aspects of the outcomes often really are more or less certain in the real-life medical situations she's using the trolley problem to illuminate.

[4] As I understand him, van Inwagen himself is probably enough of a realist about metaphysics that he should go for the first answer rather than the second. But the availability of the second is what I'm interested in here, and other philosophers do apply a Carnapian approach to questions about composition, including the question of whether there are tables. The main person for this approach is probably Eli Hirsch.

References

• Beebee, Helen (2018). I - The Presidential Address: Philosophical Scepticism and the Aims of Philosophy. Proceedings of the Aristotelian Society 118 (1):1-24.
• Foot, Philippa (1967). The problem of abortion and the doctrine of the double effect. Oxford Review 5:5-15.
• van Inwagen, Peter (1990). Material Beings. Cornell University Press.
• Jenkins, C. S. I. (2014). Serious Verbal Disputes: Ontology, Metaontology, and Analyticity. Journal of Philosophy 111 (9-10):454-469.
• Kripke, Saul A. (2011). Nozick on Knowledge. In Philosophical Troubles. Collected Papers Vol I. Oxford University Press.
• Nozick, Robert (1981). Philosophical Explanations. Harvard University Press.
• Thomson, Judith Jarvis (1985). The Trolley Problem. The Yale Law Journal 94 (6):1395-1415

Avicenna vs Turtles

Anglophone metaphysicians, and perhaps some other metaphysicians too, fairly recently started thinking about things in terms of ontological dependence. The idea is that some things depend on other things, or are grounded in those things; some facts are true in virtue of other facts, some things are fundamental while some things depend on the fundamental things, and so on. There’s a whole mess of concepts in the vicinity and we still haven’t sorted it all out, but it seemed like a useful way to think. It still does. I still think like that myself, sometimes.

One question you might ask about this framework is this:

• Must there be a funamental level? Couldn’t it just be turtles all the way down?

Ross Cameron addressed this question in a paper a few years ago (Cameron 2008). He basically came to the conclusion that he couldn’t find anything incoherent about everything being grounded in something further down, but it’s an inelegant set-up and we should expect the world not to be like that. When I’ve come across people citing his paper it has mostly been to agree with his conclusion, although this impression may be unrepresentative or at least out of date. I like the paper too, and I’m pretty sympathetic to his take on the issue: metaphysical systems don’t have to be incoherent to be implausible.

Now, Cameron wasn’t the first person to think about this sort of thing. He mentions some predecessors in the paper, but today I’m going to talk about one he doesn’t mention. About a thousand years ago Avicenna was coming up with a proof of the existence of God, like you do, and his proof involved thinking about something structurally quite similar to the turtles question and coming to the opposite conclusion over whether there has to be something at the bottom. He thought the infinite descent scenario really was incoherent. Since one can count the people cleverer than Avicenna on the fingers of one hand, if he’s challenging our contemporary consensus we should probably take a look at what he had to say.

I’m not an Avicenna scholar, unfortunately. My knowledge of Avicenna comes mostly from a podcast by one Avicenna scholar (Adamson 2010-, especially #138-142) and a book by another (McGinnis 2010). I’ve also read a few passages from Avicenna’s own work in translation, including one on the argument I’m talking about here (McGinnis and Reisman 2007, especially pp214-5). It’s not nothing, but you probably won’t find me trying to turn this blogpost into a paper. (But if you’re an Avicenna scholar and think there’s something here worth tackling properly together, I’m not busy.) You might wonder why I’m writing about it at all, given my incompetence to do the topic justice; it’s basically because it seemed like there was something there and nobody else seemed to be writing about it. Maybe that’s because the medieval-philosophy-in-Arabic crowd and the contemporary-analytic-metaphysics crowd don’t overlap much. Anyway, if you think I’m talking rubbish but not such irredeemable rubbish as not to be worth engaging with, we can have a discussion in the comments or wherever and try to understand the issue better.

So, here’s Avicenna’s argument as I understand it.

1. He’s got a distinction between things which are necessary through (or in) themselves and things which are necessary through another. He’s not understanding necessity the same way philosophers do nowadays - possible worlds and all that - but I wouldn’t like to try to explain exactly how he is understanding it. It seems at least to be structurally a bit like something related to our contemporary concept of ontological dependence, though.
2. He thinks that everything is either one or the other, and nothing is both. In terms of ontological dependence, you can think about things that depend on something else, and things that don’t.
3. He wants to show that at least one thing must be necessary in itself. He’s going to go on to argue that various things follow from something being necessary in itself, and that there can only be one such thing, and he’s going to say that this necessary existent is God. But for the moment he just wants to show that there’s at least one.
4. We know that something exists. Look around yourself, look within yourself, whatever. Something exists.
5. Now gather everything together that is necessary through another. If there aren’t any such things, then since something exists, something must be necessary in itself. But if there are, then gather them together into one big object. (We should resist the temptation to call this object The Great Mumkin.)
6. Is this object necessary in itself, or through another? If it’s necessary in itself, then we’re done. If not, then what is it necessary through? (I’ve seen this step presented in different ways, and Avicenna may have presented it himself in different ways. He actually thinks it’d be absurd for the sum of all things necessary through another to be necessary in itself, but it’s worth noting that we don’t have to agree about that for his argument to work.)
7. If it’s necessary through a part of itself, that’s either absurd or counts as the part being necessary through itself. (I’m not really sure how this step goes, and it seems to me that it’s where most of the action is.)
8. If it’s necessary through something that isn’t part of it, then that thing must be necessary in itself, because everything else is a part of it.
9. So whichever option we go for, something is necessary in itself.

Now, I expect I’ve garbled the argument somewhere. The bit where we say that things can’t be necessary through a part of themselves seems especially dodgy. Here’s a worry: take the sum of everything that exists. Is that necessary in itself, or through another? If anything besides God exists, then it can’t be necessary in itself, at least according to Avicenna, because he` thinks only one thing is, and that thing is God and doesn’t have proper parts. But if it’s necessary through another, then that other thing must be a part of it, because everything is. But that’s not supposed to be allowed. So I don’t really get what’s going on there. (I guess he could say that in this case we choose the option at step 7 of the part being necessary in itself. But I do think I’m missing something here.)

One way of patching this is to say that everything is either necessary in itself, or is necessary through another, or is the sum of something necessary in itself and something necessary through another. (I’m using a pretty classical-mereology framework, because Avicenna seems to be. To call Avicenna a classical mereologist would be anachronistic by 900 years or so, but the argument helps itself to principles that are accepted by classical mereology but rejected in some non-classical mereologies. If classical mereology rules out turtles all the way down, that’s interesting in itself. Investigating which mereological principles are essential to the argument and which aren’t would be interesting too, and if the argument has something in it then it’s something we should do.) If we make this assumption, the argument still goes through much the same. You just include the mixed option in step six, and note that the mixed option also entails that something is necessary in itself. The sum of all things would be the sum of the Necessary Existent, which is necessary in itself, and Creation, which is necessary through another, viz. the Necessary Existent.

With different mereological assumptions you might also try constructing the sum-of-all-dependents object by removing everything necessary in itself and taking what’s left. That relies on a complementation principle you might want to reject (but which classical mereology accepts), but it’s worth noting the option. That object might not contain all dependents - if there’s a dependent object that is part of a necessary object, for example - but if it depends on something outside itself then something is outside it, and so something is necessary in itself because everything outside it is part of the sum of things necessary in themselves.

Anyway, let’s adapt Avicenna’s argument to the question of whether everything might be dependent on something else. We’ll call things that are dependent on something else dependent, and other things independent. We’ll allow mixed cases, and assume classical mereology (though not atomicity - there could be gunky things all of whose parts have proper parts).

1. Something exists.
2. If there are no dependent things, something is independent and we’re done. Otherwise take the sum of all dependent things.
3. If it’s independent or mixed, we’re done. So assume it’s dependent. What’s it dependent on?
4. If it’s dependent on something that isn’t part of it, that thing must be independent or mixed, and we’re done.
5. If it’s dependent on something that is part of it, that’s either absurd or counts as it being independent or mixed. (This is the dodgy step.)

In Cameron’s paper, he does sort of address a version of the summing-the-dependents objection, although not with particular reference to Avicenna. Let’s look at what he says:

Another potential justification for the intuition is familiar from the debate between Leibniz and Hume. Here, the thought is that if there could be an infinite chain of entities e1, e2, e3, ... such that e1 is ontologically dependent on e2, and e2 ontologically dependent on e3 etc, then, while every entity in the chain is grounded, nothing grounds the chain itself. Even if there needn’t be a first member of the chain – an independent entity that provides the ultimate ontological grounding for every member of the chain - there must be an ontologically independent entity to ground the existence of the chain itself.

But that’s unconvincing. Grant for the sake of argument that not only must every being on the chain have an ontological grounding but the chain itself must have an ontological grounding. This doesn’t entail that anything is an independent entity. Perhaps the chain of entities e1, e2, e3, ... depends on a further entity ea1 which depends on ea2, which depends on ea3 etc? And if someone asks “but what about the chain ea1, ea2, ea3...?” we can appeal to a new entity eb1 which is the ontological ground of this new chain, and which depends on eb2 which depends on eb3 etc. And so on. In each case, the infinite chain of entities is dependent on an entity which is itself the first member of another infinite chain. Provided we’re prepared to postulate more and more entities, one for every cardinal number, then nothing will go ungrounded. (Cameron 2008: 11)

I don’t think this works against Avicenna’s version of the objection. The problem is that mereology isn’t like set theory. (The reference to “one for every cardinal number” is talking about the way set theory deals with this kind of thing.) In set theory you can’t just gather all the things of a certain kind into a set and ask questions about it. You get Russell’s paradox and others if you allow that. But in mereology you can gather all the dependents together into a sum and ask questions about it. You don’t get the paradoxes, and in fact accepting unrestricted mereological composition is fairly popular among people who work on the topic. (The difference basically arises because the set of all Xs can’t have members that aren’t Xs, but the sum of all Xs can have parts that aren’t Xs. For example, the sum of all cars has parts that are wheels, not cars.) Since mereology allows this kind of comprehension principle, it doesn’t help to postulate more and more entities as Cameron suggests. Anything you postulate will either be part of the sum-of-all-dependents already or won’t be a dependent. There are issues about infinite extensibility and unrestricted quantification which might apply here, but our understanding of that is much less settled than our understanding of set theory, and moving from the difficulties of unrestricted quantification to the impossibility of unrestricted composition is a leap that would need some heavy-duty justification. I think it’s fair to say that in light of Avicenna’s version of the argument, Cameron hasn’t really said enough here to fend off the objection.

So I guess bringing Avicenna into the debate wasn’t a complete waste of time. But might there be something else wrong with Avicenna’s argument? The argument looks pretty solid, at least given the assumptions about mereology, except for the step at the end. Why shouldn’t an object be dependent on something that’s part of it? There are a couple of structures we can imagine as challenges to Avicenna’s picture.

• Gunk: everything is dependent on its proper parts taken together, and everything has proper parts. So everything is dependent on something.
• Turtles: reality is made of the earth sitting on top of an infinite descending series of turtles. Everything is dependent on the sum of the things its parts depend on, and everything is dependent on any segment of the series unbounded below and wholly strictly lower than it, if any. So the earth is dependent on the sum of the turtles, the top turtle is dependent on the sum of the other turtles, and the whole of reality is dependent on the sum of the turtles but not on itself (since nothing depends on the earth), and the sum of the turtles is dependent on the sum of the turtles other than the top one. (There are some issues to go into about overdetermination, joint dependence and so on, but I think it should be possible to fill in these details in this general picture.)
• If you prefer, you can work with Simple Turtles: reality is a mereologically simple earth above a (not densely ordered) infinite descending series of mereologically simple turtles. Everything depends on the sum of everything strictly below its top part.

That wasn’t so hard. What was Avicenna thinking? Three possibilities come to mind:

• He had a notion of necessity-in-itself which rules out these structures.
• He had a notion which doesn’t rule out these structures but he didn’t think of them.
• He had a notion which doesn’t rule out these structures but had other substantive commitments that do.

All are prima facie plausible, though the second is uncharitable. Avicenna scholars will have views, but I’m not in a position to say what those views would be. But we can still think about how we should respond to these cases.

It’s worth taking the gunk and turtle cases separately. With gunk I think the best thing to do is just admit defeat if we’re allowing that things can depend on their proper parts. I think composition is identity, and things don’t depend on their parts: things are their parts. (Gunk is a bit weird if composition is identity, but I don’t see that it’s incoherent. Indeed, I don’t see that you couldn’t have gunky pluralities even if composition isn’t identity. Regular readers will be familiar with gunky pluralities from the previous post.) If you don’t think composition is identity - and if you’ve worked in the area then you probably don’t - then you might adopt some other substantive commitment linking mereology and dependence, like saying if an object depends on a part of x it depends on x, and so if things depended on their parts they would depend on themselves, which tends not to be allowed. But if you think things can depend on their parts, I guess you’re welcome to think the gunk example undermines the Avicennan argument. (And Avicenna does seem to think things depend in some way on their proper parts, which is part of why the necessary existent can’t have proper parts. I definitely feel like I’m missing something.)

With Turtles and Simple Turtles there isn’t really a ready-made metaphysical thesis like composition as identity that I can wheel out to undermine the argument. So what can we say? Well, I don’t have a great answer, but I do think that even being able to ask the question moves the debate forward a bit in terms of where you can apply pressure. The problem Cameron had with turtles all the way down was that it’s theoretically uneconomical: you can’t have one base explaining everything, because the base needs a separate explanation, and so on forever. It’s inelegant. But now we have a different objection: Turtles isn’t just inelegant; it’s weird. And where there’s weirdness, there might be Rationally Compelling Metaphysically Necessary Principles to rule it out. If you can think of one, feel free to put it in the comments.

References:

• Adamson, Peter (2010-present): The History of Philosophy Without Any Gaps. Podcast. Historyofphilosophy.net.
• Cameron, Ross P. (2008). Turtles all the way down: Regress, priority and fundamentality. Philosophical Quarterly 58 (230):1-14.
• McGinnis, Jon (2010). Avicenna. Oxford University Press.
• McGinnis, Jon & Reisman, David C. (eds.) (2007). Classical Arabic Philosophy: An Anthology of Sources. Hackett.