1. Permissivism

First, a few words about our permissivism.

The label ‘permissivist’, like ‘conservative’ and ‘eliminativist’, picks out a broad and heterogeneous family of theories about the structure of the material world.Footnote ² (We might mention in passing two parameters along which one might be permissive. One concerns composition – the permissivist about composition, the ‘universalist’, will think that any plurality of material objects compose a further object. Another concerns the abundance of coincidence – here, the permissivist allows for a multitude of coincident material objects whenever there is any material object. This kind of permissivist standardly holds that the variety of coincident object have divergent, often radically divergent, essences.)

The locus of the disagreement between conservatives and permissivists is sometimes framed in terms of a question about perception. For example, at one point Korman describes the permissivist as claiming that ‘there are countless highly visible macroscopic objects right before our eyes’.Footnote ³ However, we wish to emphasize that permissivism is itself neutral about such perceptual claims. Even granting, for example, that there are myriad objects that are mereologically coincident with a certain tree, it is far from straightforward to conclude that we see each of them whenever we see that tree. Best not to burden the permissivist, then, with controversial theses in the philosophy of perception.

Conservatives are often presented as the friends of common sense, and permissivists as far less friendly (though Korman himself is cautious about this).Footnote ⁴ But, again, it is far from clear whether common sense takes a stand on extraordinary objects. Even granting that common sense does not commit itself to a certain class of extraordinary objects, it remains to be seen whether it is antithetical or merely neutral in regards to the question of their existence. Granted, they do ‘escape our notice’,Footnote ⁵ at least ordinarily. But why, then, suppose that by the lights of common sense, they seem not to exist? We will not then presume that conservatism is the position of common sense, but we won't pursue this issue further.

Finally (roughly in line with the two parameters mentioned above) Korman distinguishes two subcategories of permissivism. The ‘doctrine of plenitude’Footnote ⁶ says that for any function from worlds to filled regions in those worlds, there is an object that exists at exactly those worlds and exactly occupies those regions at those world (this straightforwardly entails a kind of liberalism about spatiotemporal coincidence, at least assuming there are multiple possible worlds).Footnote ⁷ The doctrine of universalism says ‘for any object there is an object composed of those objects’. He goes on to say that the doctrine of plenitude entails universalism.Footnote ⁸

However, this isn't quite right, since at least the occupational formulation of plenitude in Hawthorne's Metaphysical Essays is silent on the mereological relations between region-occupants. That said, we both have some sympathy with both universalism and plenitude as defined, but we do not wish to suppose that there are no other interesting versions of permissivism beyond those built out of some combination of occupational plenitude and mereological universalism. Still, that combination gives a good flavour of our theoretical leanings and we shall not in this paper be examining the comparative merits of various ways to develop a radically permissivist outlook.Footnote ⁹

2. Epistemological Arguments Against Conservatism

One potential line of attack against conservatism is epistemological. Roughly speaking, the argumentative strategy is to argue that if conservatism is true, then various of our ontological beliefs are in epistemic trouble. (The details will depend in part on the target ontological beliefs: those of ordinary people, or those of the metaphysician who propounds conservative views, or both? Beliefs about what there is, or beliefs about what there isn't, or both? And so on.)

A very natural broad-brush way to pursue this kind of argument is to appeal to ways that our ontological views are contingent on the vicissitudes of our social, cultural and/or biological milieu, and the observation that as we move across modal space, variation in these parameters induces variation in ontological views, without corresponding variation in the metaphysical structure of the world. Contingencies in whether we recognize things essentially suitable for holding flowers (as we ordinarily do) or whether we recognize car-shaped things essentially contained in garages (as we ordinarily do not) may not correspond to contingencies in whether there are such things.

Assuming a sufficiently extravagant version of permissivism, there is prima facie no problem here: there is something for everyone, so to speak. For any modal profile we might cook up, there will be something in the world to answer to it, at least according to plenitude-friendly picture thinking. But if only a select few of the candidate modal profiles are actually instantiated in the world – as the conservative would have us think – then then it is much harder to be charitable towards our counterparts with divergent metaphysical perspectives. Given conservatism, if we are right, then our counterparts, almost certainly, are wrong. Aren't we at best lucky to be getting at the truth? And isn't that kind of luck incompatible with knowledge?

We can easily imagine the plenitude lover being tempted by this kind of argumentative strategy. However, we do not think that it is especially promising. Let us briefly say why we're pessimistic.

An obvious point to begin with is that some luck in acquiring the truth is by no means straightforwardly incompatible with knowing the truth. If by sheer luck you turn your head in a particular direction and see someone robbing your home, that hardly precludes you knowing that there is someone robbing your home. The key issue, then, is whether the kind of luck in question is incompatible with knowledge. And here we are very skeptical. The most compelling cases where luck is incompatible with a true belief counting as knowledge are cases where very minor tweaks in the environment would have induced a false belief. For example: suppose that someone is only barely under six feet tall, and you believe that they are under six feet tall, and furthermore you would have also believed that they were under six feet if they were exactly six feet – the kind of proneness to error in this case is suggestive of a lack of knowledge. But if instead, you have a true belief about a subject matter where you would have had a false belief if you had gone to Harvard, or had been born into certain cult-infused households, or had been instructed in a different religious tradition, that kind of proneness to error seems far less indicative of an absence of knowledge. (For those thinking of knowledge in a safety-theoretic way, this gives us the following heuristic: the relevant ‘close’ worlds that test for knowledge are ones that are not allowed to vary very much as far as the process of belief-fixation is concerned.) And prima facie, the proneness to error made salient by vicissitudes in culture, biology, and so on is more akin to the family of examples that are epistemologically less damaging.

Now, there may nonetheless be some cases where the vicissitudes in ontological belief-fixation are so close to hand as to be more obviously knowledge depriving. Suppose for example – and this is not especially far fetched – that various ordinary people oscillate between asserting something along the lines of ‘Ships cease to be when they sink’ and ‘Ships continue to be when sink, its just that they need a whole lot of work to become seaworthy again’. Given a conservative metaphysics, one will struggle to find a plausible contextualist semantics according to which both speeches are true. If, when adopting one perspective, one is in real danger of the other, then this may indeed be a case where one is too lucky to know.

However, we see no compelling general argument to the effect that, assuming conservatism, true beliefs are too epistemically precarious to count as knowledge. In the sinking ship case, the danger of error is much more live than need generally be the case assuming conservatism and a general dependency of ontological views on culture, biology, etc.

We would like to introduce one further theme. Even supposing that a community has seriously misguided views about when things come in and out of existence, that need not at all mean than that propositions they express by claims of the form ‘There are Ns’, where ‘N’ is a natural kind term in their language, are false. Consider an example inspired by Korman's own discussion: suppose a community has the word ‘uptree’, and further suppose that there are trees. When the community is in the presence of an upright tree, the members of the community say ‘There is an uptree’. And when the tree topples over, the community say ‘The uptree has just ceased to exist’. The community also says things like ‘Uptrees are essentially upright’. Suppose we embrace some sort of conservatism according to which there are trees, but there is nothing coincident with an upright tree that is essentially upright. What should we make of this community?

Here is one point that bears emphasis: insofar as ‘uptree’ is functioning as a kind of natural kind term, we should say that members of this community are speaking the truth when they say ‘there are uptrees’. We think the most reasonable semantics here is one according to which the word ‘uptree’ picks out the kind tree, and the community just has incorrect views about the essence of trees. (People similarly had incorrect views about the essence of gold and of stars, but that does not dissuade us from taking the kinds gold and stars to be the designata of the relevant natural kind terms in their mouths.) What this ultimately means is that claims of the form ‘there are Ns’ – for example, ‘there are trees’ – are particularly non-precarious sorts of claims. Wildly incorrect views about essence will not by themselves stop such claims from being true. (Of course, if simples arranged treewise composed nothing at all, that would be a different matter! The point is that merely having wildly incorrect views about essence does not make for the falsity of one's existential claims.) Thus, claims like ‘there are trees’ ought, by conservative lights, count as especially stable in truth value across modal space, even if views about essence and persistence conditions vary quite wildly across that space.

Since we are not optimistic about epistemological arguments against conservatism, epistemological principles and premises are unlikely to constitute the central battleground in our fight for plenitude. We ultimately agree with Korman on this front: the plenitude lover has no good argument to the effect that she is on epistemically firm footing, but the conservative's position is epistemically unstable. That said, we have some misgivings about Korman's epistemological remarks, some of which we briefly indicate below.

3. Korman on Debunking

Korman anticipates that the central thrust of the epistemological critique of conservatism has to do with a lack of explanatory connection between the subject matter of ontological beliefs and the beliefs themselves. As he sees things, the lack of such a connection is epistemologically bad news, and the acknowledged lack of a connection is especially bad news, because it constitutes a ‘defeater’ of one's ontological beliefs. He then considers something like the following argument being run against conservatism by the permissivist: our ordinary ontological beliefs are dictated by the contingencies of biology, culture, etc, and not by the metaphysical fabric of the world that constitutes the subject matter of the relevant beliefs. (i.e. there is no ‘alethic explanation’ of our beliefs). Neither is the metaphysical fabric of the world (except perhaps in special cases) dictated by our doxastic makeup (i.e. there is no ‘doxastic explanation’ of the facts of ontology). This is (the argument goes) especially bad news for the conservative, insofar as the conservative rests his case on the epistemic good-standing of ordinary ontological beliefs. This is at least very close to what Korman calls the Debunking Argument against conservatism.

As we read him, there are three main threads running through Korman's discussion of the debunking argument. First, he argues that the permissivist would also be in epistemic trouble were there no explanatory connection between our ontological beliefs and the world. Second, the plenitude lover has no special advantage vis-à-vis the conservative in making room for such an explanatory connection. Third, the conservative can make room for a suitable connection: Korman's own proposal is that we directly apprehend the relevant facts of metaphysical structure. (Although the details of how this works are bound to be a little elusive, he provides a proto-theory of the explanatory connection that the conservative needs.)

Korman devotes much of his attention to the first thread. He argues that familiar and tempting arguments for permissivism rely just as much on the epistemic good-standing of our ordinary ontological beliefs, and so the permissivist who wishes to motivate her view thus is largely in the same boat as the conservative with respect to the debunking challenge. As we read him, he thinks it is not promising to try to put our ontological beliefs on firm epistemic footing simply by populating the world with so many objects that we are not lucky to hit the mark. For even if we are not lucky in this sense, a lack of explanatory connection between ontological beliefs and their subject matter is still bad news for those beliefs. (By analogy, positing a pluriverse so rich that pretty much any belief of the form ‘Somewhere out there, an alien is doing F right now’ was true at this and other close possible worlds would not suffice to put those beliefs in good epistemic standing.)

As we said above, we already agree that there is not a promising line for the permissivist here. But, nonetheless, we still have some misgivings about framing the epistemic issues in the vicinity in terms of ‘explanatory connections’, as Korman does. Here briefly are some of our worries:

First, it does not seem especially clear that knowledge of a subject matter requires either an alethic or a doxastic connection between subject matter and belief. When we know something about the future, it is not quite the subject matter of the belief – i.e. facts about the future – that explains the belief.Footnote ¹⁰ (Of course, one might relax things: perhaps it is good enough that the belief be explained not by its subject matter, but instead by something that explains its subject matter. But then one might think, by parity of reasoning, that it might also be good enough that our belief in tables be explained by something that constitutes its subject matter rather than the subject matter itself. Once the alethic dimension of the explanatory requirement is relaxed in this or that way, it may be too weak to be interesting.)Footnote ¹¹

A similar worry is made vivid by thinking about beliefs about logic. It seems far from clear to us that one's belief in some principle of logic – say, universal instantiation or an S4 principle of modal logic – is to be explained by the fact that the belief is about. Again, one might be so lax about explanation that it becomes unmysterious how the truths of logic can explain belief. For example, one might think that pretty much any subsumption of a phenomenon under a general and non-gerrymandered pattern counts as explanation. But in that case, one can explain the fact that (e.g.) someone believes the principle of excluded middle by appeal to the fact that he believes all the basic truths of classical logic, thus giving an explanatory role to the truths of classical logic. But this renders the explanatory filter largely uninteresting.Footnote ¹² (Note also that some philosophers have provided construals of explanation that are so weak as to be of little interest in this setting. A good example here is David Lewis's ‘main thesis’ about causal explanation: ‘to explain an event is to provided some information about its causal history’).Footnote ¹³

Here is one further concern: Korman's motivating thought seems to be that there must be an explanatory connection between a belief that P and the truth that P.Footnote ¹⁴ But it seems that a belief may be justified even if properties of a proposition other than its truth explain the belief. Suppose for example, a person is sensitive to objective probabilities in such a way that he believes a proposition only when that proposition is objectively likely (note that we are not thinking of this sensitivity as going through beliefs about objective likelihood). Here it is the likelihood and not the truth of the proposition that explains the belief. But is this really so damning?

In sum, we do not think that putting things in terms of explanatory requirements on knowledge is a promising way to set things up. If the permissivist were to have opted for an epistemological critique of conservatism, it should have been along the lines of: ‘if conservatism is true, our ontological beliefs are too unsafe to count as knowledge’ rather than ‘if conservatism is true, there is no appropriate causal-explanatory connection between subject matter and belief’. (Of course, we do not think that the safety argument is promising either – but we do think it is a more helpful way to frame things.)Footnote ¹⁵

We also think it would advance the discussion on the explanatory side to pay more attention to the contrastive aspects of explanation. Suppose you believe that someone is tall. In a normal context, when someone asks why you believe someone is tall, she is asking why you believe someone is tall as opposed to, say, short or of moderate height. In this context, answers like ‘Well, I heard he plays power forward for a basketball team’ or ‘I stood next to her and she was quite a bit taller than me’ or ‘My friend told me’ are all fairly compelling answers. But there are also contexts where the contrast is a bit different. ‘Tall’ is associated with one height cutoff. But there are also myriad other cutoffs, very close to that of tallness, in the vicinity. Thus there are myriad other properties – tall*, tall**, and so on – that are or induce slightly different intensions. When one notes this, one's request for an explanation of belief might have the following implicit shape: why do we believe that this or that person is tall, as opposed to tall*, tall**, and so on?

In this explanatory context, the answer ‘because I stood next to her and she was quite a bit taller than me’ is completely unhelpful. In this context we may, for example, entertain answers along the lines of ‘Which property one picks out is highly sensitive to facts about uses of “tall” by one's community, and the object of one's belief is, in turn, similarly sensitive to those contingencies.’ We don't want to endorse this answer (perhaps ‘we have beliefs about many of those properties’ is another kind of answer).Footnote ¹⁶ But we do take the answer seriously. And notice that in that explanatory context, it is delicate contingencies about the community's patterns of use, rather than the pattern of heights, that is the central explanatory parameter. Of course, such a contingency needn't render the belief unsafe: suppose that we get up close to someone that is six foot eight, and believe that they are tall. And suppose that we very easily could have lacked that belief, but had instead had beliefs directed at other properties (tall*, etc.) on account of vicissitudes in the use of ‘tall’ by our linguistic community. That hardly threatens the safety of our beliefs – assuming that the person instantiates all of the candidate values of ‘tall’. But it does mean that, at least within a certain explanatory setting, the fact that we have beliefs that someone is tall is not very well explained by their height.

The situation for ontological beliefs is remarkably similar from the perspective of the plenitude-lover. Suppose we believe that there is a hammer in the kitchen. In the very special context in which one asks why someone's belief is about hammers rather than hammer*s, it will not be at all helpful to explain his belief by saying ‘Well, he remembers putting a hammer in the kitchen’. In this context, we may well take seriously a response according to which the main explanatory parameters are facts about the linguistic community. Meanwhile, there will be plenty of other explanatory contexts where facts about hammers do count as explaining various beliefs about hammers. (Why does he believe the hammer is in the kitchen rather than the garden shed? Why does he believe there is a hammer there rather than an axe?)Footnote ¹⁷

Further, we think an alethic answer here along the lines of ‘because we apprehend the facts’ is unlikely to be illuminating. ‘Apprehends that P’, as it is used in English, is factive and plausibly entails ‘knows that P’.Footnote ¹⁸ What does ‘apprehend’ add to ‘know’? The main thing it seems to add – as with factives like ‘realized’ – is something like the presupposition that one didn't know the proposition in question earlier. Take any context where we say ‘realized’; e.g. someone tells you an anecdote about a person's behavior and you realize that they are kind. In any such setting, ‘apprehend’ will sound tolerable: ‘At that point I apprehended that she was a kind person’. Here, switching to ‘apprehended’ doesn't clearly add anything at all to ‘realized’ or ‘comes to know’.

Granted, Korman tells us that he intends to be using ‘apprehends’ as a term of art, as ‘a dummy term for that, whatever it is, by which (the relevant metaphysical facts) non-deviantly influence our mental states’.Footnote ¹⁹ But this doesn't seem to add much to the strategy of using ‘apprehends’ as a term of art for ‘whatever it is that explains how we come to know stuff about metaphysics’. ‘Non-deviant’ is here a shout-out to the observation that sometimes a fact that P plays a role in explaining a belief that P that nonetheless isn't known.Footnote ²⁰ And ‘influence’ adds little to the expectation that the relevant metaphysics facts will play some kind of role in the complete explanatory story of such knowledge that we have. In short, we don't see that the prototheory proposed here adds mh to the demand for an explanatory connection beyond a promissory note along the lines of ‘Well, assuming we know some things about metaphysics, there is some kind of explanation of that, and the subject matter is bound to play some kind of role in that explanation’.

4. How Bizarre!

One of us once wrote:

We don't want to get too involved in recollecting authorial intentions. And certainly, the passage is wanting when it comes to clarity! But what we wish to emphasize now is that a distaste for hypotheses along the lines of ‘We got lucky!’ need not take the form of an epistemological argument of the form: ‘If we are lucky in that way, our beliefs are too lucky to count as knowledge’. And, in particular, our distaste for the luck postulated by various conservative ontological views need not take the form of ‘unless we are permissivists, we're too lucky to know’.

Let us call a hypothesis along the lines of ‘you ended up with a true belief concerning the question whether P because you got lucky in such-and-such a respect’ a luck hypothesis. By way of setup, it will be helpful to distinguish two reactions to luck hypotheses. One reaction is this: ‘if that luck hypothesis about such-and-such a belief is true, that belief is not knowledge!’. Call this the No-Knowledge reaction. Another kind of reaction is: ‘the world would have to be very bizarre indeed for the luck hypothesis to be true!’. Call this the How Bizarre! reaction. To get a flavor of what we have in mind here, consider the following two cases:

Case one: You ask someone whether there is a gas station at the end of the road, and they reply ‘Yes’. You believe them. The person then admits that they answered your question with a guess determined wholly by a coin flip: ‘Yes’ if heads, ‘No’ if tails. In this setting, one salient luck hypothesis is: your belief that there is a gas station at the end of the road is true because the person luckily flipped the coin in a way that delivered the right answer. If it is true, the belief is not knowledge. As a result, in the setting in question, it is natural to think ‘Well, at best I truly believe on account of a lucky coin flip, and that isn't good enough for knowledge! So, I've just learned that my belief wasn't knowledge.’ The No Knowledge reaction is perfectly appropriate here, but the How Bizarre! reaction is not. There would be nothing particularly bizarre about a world in which someone made a true but lucky guess about whether there was a gas station at the end of the road.

Case two: You are brought up in a small town in the Carolinas and believe that Country music has objective aesthetic value. Here is one kind of luckiness hypothesis: in fact, it does! Indeed, Country music is the only kind of possible music that has objective aesthetic value. If you had been born into other epochs or cultures, you would have believed that various other sorts of music had aesthetic value. But then you would have had a false belief. Very lucky, then, that you were born into that small town in the Carolinas!

In case two, we might try the No Knowledge reaction. But it is far from clear that such a reaction is well motivated. If the luck hypothesis here is true, it is still far from clear that the abundance of false aesthetic beliefs in other epochs and cultures spells epistemic doom for the Country music belief. (Our earlier remarks about luck and knowledge should give the reader some sense of why we think this.) But in this case, the How Bizarre! Reaction is very compelling. Reality would have to be a truly very weird place in order for Country music alone to have aesthetic value!

The distinction between these reactions is, admittedly, not fully precise. But we trust that it is not so vague as to be theoretically useless.

Let us now imagine we come across a community with a very strange metaphysical view. Members of this community think that tables exist, but chairs don't. Under dialectical duress, the Tablers are very stubborn: ‘It just strikes us that way’, they say. ‘Our perceptual systems make it seem that when particles are arranged tablewise, they compose an object, but when particles are arranged chairwise, they don't.’ When asked for general metaphysical principles to corroborate their beliefs, they demur: why should you expect our views about what exists to be undergirded by general ontological principles? We don't go in for that kind of theorizing. You are like anti-particularist ethicists who tell us that we are not able to say that an act is bad unless we have a fully general theory about the principles by which badness is determined.’

We might point out that if they had been endowed with perceptual systems more like ours, they would have treated tables and chairs on an ontological par. At this point, they advance a luck hypothesis: ‘Well, since there are tables and there aren't chairs, it is very lucky that we were born with our perceptual endowments. Please accept our ontological condolences.’

Here again we might try a No Knowledge reaction: even if the Tablers are right, their beliefs are too lucky to count as knowledge. But, as should now be clear, we aren't much taken by that reaction. If their view is correct, it doesn't seem that our mistakes would constitute a proximate enough danger of error to deprive them of knowledge. But the How Bizarre! reaction is altogether compelling. It would be completely bizarre for the world to be as the relevant luck hypothesis states. Now, of course, if the Tablers’ sensibilities are alien enough to our own, we may have a hard time making dialectical progress. ‘We see nothing intrinsically bizarre about our worldview’, they may say, adding ‘and apparently you are willing to concede that if we are right we may even know that we are right’.

Such is life. There may be some creatures that are so deep into an ontological coal-pit that we cannot drag them out of it, at least not by ordinary methods of rational dialogue. Still, we find the Tablers’ view to be a complete non-starter metaphysically – their view is far worse than merely one we think is false; it is one we all find somewhat absurd. And when pressed to explain why, at least part of our story will be along the lines of the How Bizarre! reaction: it would be quite bizarre for reality to be set up so that those guys were getting it right, and we all (permissivists and Korman-style conservatives alike) were getting it wrong.

One more piece of ground-clearing. Here is a point which is very prominent in Korman's discussion and which we have much sympathy towards. Suppose that one believes that P, and then acquires significant evidence that one's belief is too unsafe to count as knowledge. It is generally unacceptable in such a setting to then modify one's worldview in an ad hoc way, so as to make it plausible that the belief was safe after all. Suppose, for example, that you were given the name of a town when asking someone for a town within a hundred miles where one could find a Mercedes dealer. Your source then admitted to having picked a local town at random. Here, it seems that even if your belief was true, you easily could have formed a false belief in that situation, and that the relevant proneness to error is indicative of a lack of knowledge. In this setting, it would be completely unacceptable to shore up your belief by filling out your worldview with the hypothesis that every town within a hundred miles has a Mercedes dealer, and so the informant ‘couldn't miss’.Footnote ²²

By analogy, there would be something unsettling about a route to permissivism that took the form of reacting to prima facie powerful evidence that one's beliefs were too unsafe to count as knowledge by a postulation of plenitude that shored up the safety of one's metaphysical beliefs. If this were the route, it might not be quite as bad as Korman thinks. A very externalist and ‘knowledge-first’ way of thinking about the dealership situation is this: the postulation of a Mercedes dealership in every town is a bad one, since it is not in fact very likely conditional on what you actually know. The situation would of course be far more delicate if you in fact knew P, and knew that you knew P, and then got evidence E that provided prima facie support for the hypothesis that you didn't know P. In such cases, it might not be easy to decide as theorists whether such evidence destroyed the knowledge one previously had, or instead allowed one a basis to learn more about the world by finding hypotheses compatible with E and also with the proposition that one knows P. So, in a world where plenitude is true and we know that there are tables, then, on the supposition that plenitude is the most plausible explanation of why some conjunction of the form ‘I know that there are tables and E’ is true, learning E might render plenitude plausible. Still, we are willing to concede that there would be something troubling about a route to plenitude that had the appearance of a desperate strategy for shoring up the safety of one's ontological beliefs. Certainly, this path would be of very little dialectical use.

That said, it is not the route we recommend. We don't, after all, think that if conservatism is true, our beliefs are too unsafe to count as knowledge. So, the epistemological ‘shoring up’ is not called for. Our reaction to the conservative, and to the kind of luck that accompanies her worldview, is much more along the lines of the How Bizarre! reaction. The next section will help give the reader a feel for our sensibilities here.

5. Arbitrariness Arguments Against Conservatism

We turn next to arbitrariness arguments that push in a plenitudinous or permissivist direction. Roughly speaking, such arguments justify a conditional claim ‘If there are Fs then there are Gs’ by claiming that to deny such a conditional would somehow be appallingly arbitrary. These arguments then proceed to argue for Gs on the basis of the conditional premise combined with the premise that there are Fs (hereafter, the existential premise).Footnote ²³

What does the complaint of ‘arbitrariness’ come to? Very broadly, such complaints rely on a background sensibility to the effect that certain kinds of metaphysical theories are bizarre, and in particular, that it would be bizarre to think that certain kinds of variations were ontologically significant. Let us begin with an non-tendentious case, revisiting the Tablers.

Consider again someone who proposes the theory that although tables exist, and although there are atoms arranged chairwise, chairs do not exist. Atoms arranged-chairwise compose nothing at all. Such a person might go on to give the property of being arranged tablewise a starring role when answering van Inwagen's Special Composition Question: for any xs, when is there some y such that the xs compose y?Footnote ²⁴ Let us imagine that the proponent of the theory is not relying on any deep insight about the underlying structure of the atoms composing the table (eg. that although we don't realize it, when atoms are arranged tablewise they also come under the direct control of a demon, in a way that atoms-arranged-chairwise do not). Rather, it just strikes the theorist as natural to think that being arranged tablewise is ontologically special.Footnote ²⁵

Now, the Tablers’ theory is not guilty of any outright logical incoherence. But we will assume that all readers will find such a theory outlandish. We likely all share sensibilities to the effect that being arranged chairwise and being arranged tablewise are ‘on a par’ when it comes to the generation of composite objects. A view to the effect that there are neither tables nor chairs is not outlandish in this way. Neither is the theory that there are both tables and chairs. But the theory that there are tables but not chairs is not only ‘disgracefully messy’ (to use Van Inwagen's phrase) but is also alien to our shared sensibilities. Of course, we may not be able to make dialectical progress on these grounds with the proponent of this theory – absent sufficient shared sensibilities, this may be impossible. But we can well enough articulate, even to such a theorist, why such a theory seems like a non-starter to us.

Is the proponent of the strange theory being ‘arbitrary’? It wouldn't be unnatural to say that the person was being arbitrary, given the lack of any systematic basis for the theory. But it wouldn't be so unnatural either to deny that they were being arbitrary – after all, the theorist's picture is not based on capricious personal whim, at least insofar as the theory is propelled by which differences genuinely strike that person as ontologically significant. We thus think it is best not to fixate on the term ‘arbitrary’ here.Footnote ²⁶ The arguments that we are interested in ultimately rely on what we hope are sufficiently shared sensibilities about what kinds of cases are metaphysically on a par and, relatedly, on what sorts of differences are not going to be ‘ontologically significant’. Henceforth, we shall call the relevant family of arguments parity arguments.

One final point of clarification: by way of example, we looked an an outlandish answer to the Special Composition Question. But not all of our targets involve unwelcome answers to the Special Composition Question. After all, philosophers may (and often do!) agree about composition, and still disagree about the range of coincident objects. For example, two philosophers may agree on the most liberal answer to the special composition question (i.e. for any xs, there is always a y that they compose) and yet disagree either about how many objects fuse some xs, or else about which kinds of modal profiles are instantiated by objects that fuse some xs. In this case too there is a role for parity arguments. For example, supposing Socrates simultaneously runs and juggles, it would be outlandish to suppose that at that time, the atoms composing Socrates also compose something that essentially runs but to nonetheless deny that at that time, those atoms compose something that essentially juggles.

It is reasonably clear, at a high level, how one might use parity arguments to push in a permissivist direction. Thinking through things for oneself, one starts by recognizing that certain categories of things exist, and then realizes that to accept the existence of those things and to deny the existence of various others would involve attaching ontological difference-making to a kind of distinction that doesn't seem the right kind of thing to be an ontological difference-maker. And so one naturally expands one's ontological commitments to avoid unwelcome parity violations. Having thought things through for oneself, one will try to make dialectical progress with others, trusting that they will be sufficiently sympathetic to your sensibilities concerning parity.

Korman's discussion is one of few attempts (from either side of the debate) to be explicit about the formulation and prospects of various parity arguments, and so we find it especially illuminating to work through the differences between how we think about these arguments.

For his part Korman does not aim to offer any master argument against parity arguments. Rather, he looks at a variety of arguments in the family centered on familiar permissivist examples, and in each case proposes particular defensive maneuvers. Let us look at two sample arguments and extract responses to them from his discussion:

Korman's discussion suggests a different attitude to A and B.

In the case of A, he will deny what we have called the existential premise. Of course, he doesn't wish to deny that there are islands – what he does deny is that there are objects that fit the profile laid out in the first premise. While there is a case to be made, he says, that the island is no longer an island when it becomes submerged in the ocean, there is no plausible case that it ceases to exist.Footnote ³⁰ It seems that according to Korman, not only are islands not like that, but nothing is. Importantly, then, Korman's disagreement with the permissivist who wishes to run an argument like A is not apparently about whether there would be a violation of parity were there to exist something with the first profile and nothing with the second – that is, the disagreement is not over the conditional premise. Rather, it is about a particular existence claim, which might initially have seemed to be in our common ground.

On the other hand, in the case of Argument B, Korman seems likely to be suspicious of the conditional premise. His discussion suggests that there is nothing objectionable, at least in the case of artifacts, about the compositional facts depending on the intentions of the artificer. We often intend to make snowballs, but don't intend to make snowdiscalls. This, on Korman's picture, is crucially relevant to why we make snowballs and not snowdiscalls. It is, in his words ‘an ontologically significant difference’ between the cases – and so we needn't accept the second premise.Footnote ³¹

It is especially important to note that Korman is generally friendly to the idea of parity arguments. For example, he at one point considers the suggestion that there are constraints on what profiles could possibly be instantiated: that ‘no amount of intending can bring into existence something with the persistence conditions of a snowdiscall’. But this, he writes ‘does seem intolerably arbitrary, that you could make something that can be anywhere between perfectly round and roughly round but not something that can be anywhere between perfectly round and flat’.Footnote ³² Rather, he seems to be optimistic that there are no good parity arguments that begin with objects that his brand of conservatism is friendly to but which then make a persuasive case for a much more plenitudinous ontology.

As we have said, Korman's aim is not to offer a master argument against permissivism and so, not surprisingly, we have no master line of defense to offer. However, we think it would be helpful to chart a variety of reasons why we were somewhat unmoved by the considerations that move Korman. We summarize our reactions under three headings.

6. Parity Arguments and Plenitude

Parity arguments are a powerful tool in metaphysical theorizing. Although, as we've said, they rely heavily on shared background sensibilities, parity considerations in the right settings do make make trouble for various ‘middle of the road’ conservative positions about the Special Composition Question, and similarly make trouble for conservative positions concerning the temporal and modal profiles of coincident objects. But exactly how powerful are parity arguments as positive arguments for permissivism? Given a reasonable supply of paradigm existents, will our parity-theoretic sensibilities take one all the way to, for example, a radical plenitude of coincident objects or a thoroughgoing universalism about composition? This is far from clear. For example consider a plentitude so radical as allow something to be coincident with a physical object at one world but with rather more abstract objects like corporations or even numbers at other worlds. It is far from clear that parity arguments from a reasonable initial supply will get us all the way there. Similarly its not clear that parity arguments will get one all the way to a universalism that included sets and numbers in its scope. Thus we certainly do not wish to assume that our parity sensibilities will get us all the way to this or that version of radical plenitude (we have refrained from exploring the fine-tuned differences between various versions of plenitude in this paper).

Relatedly, we do not think of our metaphysical orientation as entirely driven by local sensibilities about what differences between cases might be ontologically significant. Rather, our metaphysical views are, at least in part, driven by a preference for powerful general principles. In this respect, we see metaphysics as very much like other fundamental sciences – in each case general principles provide compelling candidate explanations for a wealth of data. Parity considerations, as well as physics itself, thicken the ontological data vis-à-vis that provided by a common-sense inspection of the world. But general metaphysical principles, including those of logic and modal logic, are not to be seen as the outcome of some procedure of enumerative induction.

Our friendliness to permissivism is thus in part driven by a friendliness to general, powerful principles. This is especially clear for familiar views, like Universalism. But, similarly, radical plenitude about coincidence is attractive not just because it promises to avoid violations of parity in the sorts of cases discussed here, but because it promises a picture of the world likely characterized by powerful general principles. Of course, the task of articulating plenitude as some combination of powerful general principles is not straightforward.Footnote ⁴⁶ Some combinations of principles fail to live up to the heuristic ambitions of plenitude. (For example, principles about occupation profiles, or restricted to spatio-temporal occupants, might seem insufficient to capture a more general pattern of plenitude concerning all objects.) Others are difficult to articulate coherently at all. And still others might clash in unexpected ways with principles drawn from logic, science and mathematics. (For example, von Neumann's limitation of size principle may, given plausible assumptions, clash with a universal fusion principle in ontology.)Footnote ⁴⁷ Yet, by our lights, the search for powerful principles that systematize and explain the data is as noble an enterprise in metaphysics as physics, and in this respect we sense a marked difference between our orientation and that of Korman. He is avowedly particularist, examining each case of candidate being on its merits, but forgoing the project of crafting general ontological principles. By his lights, the ambitions of metaphysics ought to be scaled back. By our lights, one will thereby miss on the general structure of the world, which is there for the taking.

7. Concluding Remarks

We have two main complaints about Korman's brand of conservatism.

First, his particularism is altogether alien to us. Of course, that is not to say that particularism in any domain is unmotivated. The wine-maker who crafts a highly rated wine may not get very far at all with general principles – this or that combination of fruits and tannins and oakiness needs to be evaluated on its own merits. Particularism may even be well motivated in some areas of ethics. However, by contrast, particularism in physics would be an intellectual disaster. Imagine if earlier generations had thought: ‘Things sometimes go up, sometimes go down, they sometimes get hotter and sometimes cooler, but the search for general principles that explain these vicissitudes is inappropriate.’ This attitude would have led to intellectual sterility and ignorance. Our view is that metaphysics, including ontology, is much more like physics in this respect than wine-tasting. Thus, by our lights, Korman has the wrong methodological instincts.

A second and distinct complaint is that, at least by the lights of our parity-theoretic sensibilities, the kind of conservatism that Korman goes in for looks unacceptable. By our lights, all views in the vicinity of Korman's conservatism suffer from this kind of problem, regardless of the details. The view that that mountains exist but galaxies don't, or that galaxies exist but fusions of spectacles don't, requires treating cases that are (by our sensibilities) relevantly similar as ontologically very different. If in ontology you wish to treat like cases alike, permissivism remains the best game in town.