New metaphysics blog

Just to announce a new group blog on metaphysics:
Matters of Substance. The idea is that this will be a forum for a whole bunch of metaphysicians, along the lines of PEA soup, Certain Doubts, The Garden of Forking Paths, etc. Robbie, Elizabeth and I will be showing up there, as will a bunch of other awesome metaphysicians, so add it to your bookmarks!

New Leeds philosopher

I'm delighted to announce that Heather Logue will be joining the department at Leeds in September. Heather is currently finishing up her PhD at MIT, and specialises in the philosophy of mind and epistemology, with interests in metaphysics, philosophy of science and feminist philosophy. She has published on disjunctivism, as well as co-editing an anthology of classic texts on that topic.

Since I arrived at Leeds (three and a half years ago), we've made 11 permanent appointments and 5 of them have been women. That's 45%. It's really nice to be in a department where that's true, and where it's true solely because we've pursued a policy of hiring the best person for the job.

Cameron on Merricks on Cameron on Merricks on Truthmakers

I've linked before to my contribution to a symposium on Trenton Merricks' book 'Truth and Ontology' (T&O). Merricks' reply (to me and my fellow symposiasts (?), Jonathan Schaffer and Scott Soames) can be found here. Obviously, in a symposium the author gets the final word. The good thing (and the bad thing) about a blog, though, is that there can always be another word! So here I'm going to respond to some of Merricks' replies to me.

A general style of argument that Merricks makes a few times in T&O runs as follows. If truthmaker theory is true then every truth has a truthmaker; the best candidates for truthmakers for the truths in domain D are the Xs; but we shouldn't believe in the Xs; therefore we shouldn't believe the truths in domain D have truthmakers; but we should believe they're true, therefore truthmaker theory is false.

Two instances of this argument schema plug in truths about the past and negative existentials for D and, respectively, Lucretian properties and totality facts in for the Xs. In my paper, I agree with Merricks that we shouldn't believe in Lucretian properties or totality facts, but I argue that the truthmaker theorist (even if she is a presentist) can do better in each case. Merricks argues that my candidate truthmakers shouldn't be believed in either. He also makes a te quoque against me, and argues that the reasons I give for not believing in Lucretian properties rule out my proposed truthmaker for negative existentials. I'll respond to these charges.

Let's take truths concerning the past first. Given the truth of presentism, what makes it true that I was once a child? The Lucretian says I have (presently) a purely past-directed property: the property of having once been a child. In 'Truthmaking for Presentists', I argued that what is peculiar about such properties is that an object's having them makes no difference to the intrinsic nature of the object at the time it instantiates it. We should only believe in a property F, I argued, if an object instantiating F at t makes a difference to how F is intrinsically at t. Lucretian properties don't make such a difference: they only make a difference to how the bearer was intrinsically – so we shouldn't believe in them. I argued that temporal distributional properties do better: an object's instantiating a temporal distributional property at t makes a difference to how the object is intrinsically at t (thus avoiding the charge of peculiarity facing the Lucretian) but it also makes a difference to how the object was intrinsically at the previous moments of its existence (thus solving the truthmaker problem).

Why might you not like this solution? Here's an inconsistent tetrad:

1) Presentism is true
2) Objects instantiate temporal distributional properties
3) If an entity instantiates a distributional property, it extends throughout the region across which that property distributes
4) If an object extends throughout a region of some dimension, the region of that dimension exists

From (2) and (3), objects extend through temporal regions. From (4) it follows that there are extended temporal regions, which contradicts (1), which entails that only a point of the temporal dimension exists.

Abandoning (1) or (2) would just be to reject my theory, so can either (3) or (4) plausibly be given up? In my contribution to the symposium, I suggested abandoning (4). I said the presentist has to abandon this anyway, since they believe in persisting objects, and these are objects which are extended throughout time, even though the regions of time throughout which they extend do not (according to the presentist) exist.

Merricks objects that "presentists should deny that existing at a time is anything like being located at a region . . . Similarly, presentists should deny that persistence is extension throughout a temporal region. . . So they should reject the view that persisting objects are extended throughout nonexistent regions."

The invocation of location at a (I presume spatial) region suggests that Merricks is thinking of my view as one where objects stretch throughout time just like they stretch throughout space, even though extended regions of time do not (unlike extended regions of space) exist. But certainly, I never urged the presentist to hold that view! The sense in which I claimed the presentist must hold that objects are extended throughout time is a trivial one: they must believe that there are objects which are not instantaneous existents – objects which do exist and either did or will exist at some past or future time. Call this extension through time. The presentist believes in the possibility of extension through time, in this sense, without extended regions of time existing. So in this sense of 'extension', (4) is definitely false, according to any sensible presentist. My point can basically be put as a challenge to those who see a tension between presentist and truthmaker theory: give me an argument that I should accept (3) for any sense of 'extension' stronger than this one. I grant (3) in this trivial sense of 'extension', but then (4) is obviously going to be denied by the presentist. And there are senses of 'extension' like the way an object extends through space which make (4) true, but then I don't see why I must accept the corresponding reading of (3). The burden of proof is on one who is pushing the inconsistent tetrad: tell me the sense of 'extension' you have in mind, and give me an argument as to why I should accept both (3) and (4) – until then, I'll continue to believe my account reconciles truthmaker theory with presentism.

Let's turn to negative existentials. Following this earlier paper, I argued that the truthmaker for claims of the form 'There are no Xs' is the world itself. The view is that each positive truth has a truthmaker, and that the world is essentially composed of all and only these truthmakers. Furthermore, the world is essentially maximal: it is necessarily a world, necessarily the largest thing there is – i.e. it is necessarily composed of all the truthmakers for the positive truths. So it can't be a proper part of any other thing. That means that, necessarily, the world can only exist if all and only the truthmakers for the positive truths are all and only the actual truthmakers for the positive truths. And so, since an actually true negative existential couldn't be false without some actually false proposition being a positive truth requiring a truthmaker, the world suffices as a truthmaker for all the true negative existentials.

Merricks objects to this proposal by objecting to the property of being a world. He says this is "a totality property, equivalent to being such that there is nothing more in the universe. So Cameron's world resembles the totality state by exemplifying a totality property essentially. . . Thus what Cameron calls 'the world' is nearly the same thing as the totality state." And hence I haven't really made any advance over Armstrong's totality states. And then there's the te quoque: the property being a world makes no difference to the intrinsic properties of its bearer at the time of instantiation, hence by my own lights (as seen above, RE Lucretianism) it's peculiar, and so my own principle tells us not to accept my own ontology. Ouch!

I think Merricks' objections here are misplaced. (In fairness, I should point out that he makes some others that I am not responding to here.) Merricks objects to the property of being a world. But I didn't appeal to any such property: I only appealed to the world!

I'm assuming the following kind of picture. The reason a truthmaker theorist admits properties into her ontology is to ground accidental predications. The reason we need to admit a property of being charged is to make true truths of the form 'X is charged' – but one only needs the property because X is merely accidentally charged: were X essentially charged, X itself would be an acceptable truthmaker for 'X is charged'. If every charged entity is essentially charged, we simply don't need to admit the property of being charged – the charged entities are ontology enough. It's only because the charged things might not have been charged that we need to admit the state of affairs of them being charged (which involves the existence of the property), to provide a necessitating truthmaker for the fact that they are charged.

There's only one thing that's a world, and it is essentially a world. So I deny that we need to admit a property of being a world. The world is ontology enough. That is why my view is perfectly compatible with the principle that mandates my rejection of Lucretian properties. It's also (one of the reasons) why I think I have an advantage over Armstrong's totality states view (for other reasons, see this paper): I am merely attributing a more robust essence (but in familiar ways) to an entity many of us already believe in – I am not introducing a peculiar property for the sole purpose of solving some truthmaker problem.

Finally, I'll say something about possibilism and modal truth. In T&O Merricks makes what seems to me a very odd claim: that admitting mere possibilia to ground truths concerning what might have been is no use, because both actualist and possibilist alike should, if they are to be truthmaker theorists, hold that what is actually true depends on what there actually is. Hence actual truths concerning what might have been must be grounded in actual ontology – and so admitting mere possibilia is no help to securing the truthmaker thought.

I see no reason why a possibilist who wants to be a truthmaker theorist should hold that actual truth depends on actual being. Actual truth is just truth, so this principle is just that truth depends on actual being. I think that should only be acceptable to a truthmaker theorist if they hold that actual being exhausts being simpliciter. The truthmaker thought, I think, is just that truth depends on ontology: and the truthmaker theorist should be able to appeal to whatever ontology they believe in, whether actual or merely possible, present or past, etc. The only reason for a truthmaker theorist not to appeal to the Xs to ground some truth is if they don’t believe in the Xs.

I made the following analogy to illustrate this. Would anyone think it a good demand that the truthmaker theorist ground truths concerning what goes on at other places only in ontology that exists here? I considered the proposition 'It's raining on the other side of the world', which is true in Australia. Should we demand that Armstrong account for this truth only by appealing to entities that are located in Australia? Surely not! Surely, Armstrong is at liberty to appeal to all the entities he believes in to ground this truth, no matter where in the world they happen to be located. Only a here-now-ist should believe that the only entities to be appealed to in truthmaking are ones that exist here.

Merricks objects to the analogy because he denies "that propositions are true at places". (He points out that were he an eternalist he would deny that propositions are true at times.) But I don't need to commit to propositions being true at places in any objectionable sense in order to make the analogy. My point is just that modal truths should be treated by the possibilist just like truths concerning what goes on at other places should be treated by all of us who deny here-now-ism. There's a perfectly good sense in which 'It's raining on the other side of the world' is true in Australia and not in the UK (given that it's raining in the UK, not raining in Australia, and that Australia is the other side of the world to the UK and vice-versa); there's a perfectly good sense in which 'Gordon Brown is now the Prime Minister of the UK' is true at the present time and not true 10 years ago; there's a perfectly good sense in which 'It's merely possible that there are talking donkeys' is true at this world and not at a world containing talking donkeys. Those are the pre-theoretic data; the philosophical work to be done is spelling out what this amounts to. I agree with what I take to be Merricks' thought: that what we should say in each case depends on what we think about the ontology of places, times and worlds, respectively. If you are a here-now-ist/presentist/actualist you should say that propositions are true at locations/times/worlds; if you are sensible/an eternalist/a possibilist you should say that the propositions expressed by these sentences at one location/time/world are different from the proposition expressed at a different location/time/world, and that the proposition expressed is true or false simpliciter, and not at a location/time/world. But the point remains: whatever we who deny here-now-ism say about my sentence, so should the possibilist say about modal claims. And so I can't see any more reason to insist that the possibilist appeal only to actual ontology in accounting for modal truths than I can see to insist that Armstrong only appeal to Australian ontology in accounting for my truth.

Anyways, Merricks' reply had loads of interesting stuff in it - these are just my initial thoughts about how best to respond.

Indeterminate truthmaking

Recently, I’ve been thinking a lot about how to think about truthmaker theory if there’s ontic indeterminacy. If you thought that p’s being indeterminate amounted to p’s lacking a truth-value and you were a truthmaker maximalist, your life would be quite easy: you could say that ‘p is indeterminate’ is true just because there’s neither a truthmaker for p not a truthmaker for not-p.

But I, following Elizabeth and Robbie’s work, have committed to the view of ontic indeterminacy whereby ‘p is indeterminate’ does not entail a truth-value gap. ‘Indeterminately, p’, on this bivalent view, is compatible with both the truth of p and the falsity of p. p is either true or false, it’s just unsettled which.

On this view, there’s a gap between truth and determinate truth, and it’s an interesting question in that case what the truthmaker theorist should say. One option is that ‘Indeterminately, p’ and ‘Determinately, p’ just get treated like any other proposition, and get assigned possible truthmakers, but I prefer the option that says we should assign possible truthmakers only to the ‘indeterminacy free’ propositions, and determine the truth-value of the ‘determinacy involving’ propositions based on whether those truthmakers determinately exist or exist but not determinately so.

So the idea is that, e.g., the state of affairs of Ball being red makes it true that Ball is red. And if it’s determinately true that Ball is red that’s not because there’s some further thing, the state of affairs of Ball being determinately red, but rather because the state of affairs of Ball being red is a determinate existent. The thought being that if p is determinately true at one world and true but not determinate at another, it is difference in being enough if the truthmaker for p is a determinate existent at the former world and a mere existent (one which exists, but not determinately so) at the latter. (You can think of this as a difference in the way that the truthmaker exists, or alternatively allow yourself extra ideology – see section 7 of this paper.)

Now, if every proposition got mapped onto exactly one possible truthmaker, life would be simple. But it doesn’t, and it’s not. p might be determinately true not because there is some truthmaker for p that determinately exists but rather because it’s determinate that there exists some truthmaker for p. The case I’m most interested in is the open future. If there’s a fixed past but open future then, I say (see my joint paper with Elizabeth), there’re a bunch of candidate states of the world being a certain way throughout history that agree on how things were and are but disagree on how things will be, and it’s determinate that exactly one of these states exists, but indeterminate which.

It’s determinate that young Earth creationism is wrong because there’s determinately a truthmaker for ‘Dinosaurs existed millions of years ago’ – but there’s no determinately existing truthmaker for that proposition. Each candidate state would make that true, and it’s determinate that one exists, so it’s determinate that it’s made true. ‘Martian colonies will exist in a hundred years’, on the other hand, is neither determinately true nor false, since if a certain candidate state exists it will be made true and if another exists it will be made false, and it’s not determinate which exists.

Exactly one of these candidate states gets things right – it gives us the actual history of the world – so that state exists and all the others don’t. But none of them get it determinately right or wrong, so the existent state is a mere existent and the non-existent states mere non-existents. But saying this doesn’t tell us that it’s determinate that exactly one of these states exists, so we need to either take that as a brute fact or admit a disjunctive state of affairs – the state of affairs of this world state existing or that world state existing or . . . etc – and proclaim it to be a determinate existent.

A decision has to be made when it comes to non-existence. Truthmaker theorists disagree as to whether to admit truthmakers for negative existentials or to let explanation bottom out at facts about what there is not as well as facts about what there is. But either way, the story is going to be more complicated once it can be indeterminate what there is.

Suppose a determinately exists, b exists but not determinately so, c fails to exist but not determinately so, and every other possible existent determinately fails to exist. If you are not a truthmaker maximalist and want to take facts about what there is not as brute you still have to be able to distinguish between the mere non-existence of c and the determinate non-existence of d (say). If you were inclined to believe in two ways of being – determinate and mere being – you should now postulate two ways of non-being – determinate and mere non-being. On this view, to completely determine a world, what God has to do is to say of every possible being which of the four ways of being or non-being it has: once He’s done that, He’ll have settled everything there is to settle. (At least provided that the disjunctive states of affairs mentioned above number amongst the possibilia.)

Now suppose we are attracted to maximalism. Since a and b are the only things there are, we must admit the existence of the second-order totality state of affairs of a and b being the only first-order things that there are. Now for Armstrong, you can stop there: there’s no need to posit an additional third-order totality state of affairs saying of the second-order totality state of affairs that it’s the only second-order totality state of affairs that there is; that’s because it’s necessarily true that there’s only one second-order totality state of affairs, and hence it can itself make it true that it’s the only one. And so there’s no risk of regress. But if it’s not determinate what there is, it will likewise not be determinate what second-order totality state of affairs exists. In our situation it’s not determinate that a and b are all the things there are: both the totality state of affairs of a being the only thing, and of a, b and c being the only things, are non-existents, but they are mere non-existents. However, since it’s determinate that exactly one of these totality facts exists we can’t stop at the postulation of the second-order totality state of affairs; we need to admit a new entity: the disjunctive state of affairs of one of these three totality states of affairs existing. And now we need another new entity – a third-order totality state of affairs – that says that everything we’ve talked about so far are all the things that exist at levels one and two. In essence, this third-order totality state of affairs is the thing that makes it true that all the candidate second-order totality states of affairs are all the candidate second-order totality states of affairs.

Now, our story can stop here if it’s necessarily true that whatever third-order totality state of affairs exists, it is determinately the only third-order totality state of affairs that exists. But if it’s possible for there to be higher-order indeterminacy in what there is – that is, if it’s possible that it’s indeterminate not just what the totality of entities is but what the candidate totalities are – then the third-order totality state of affairs itself may be a mere existent. There could be other candidate third-order totality states of affairs, and it not be determinate which of them exists. But it will be determinate that one of them does . . . and so we’re off on a regress. Now personally, I doubt the coherence of higher-order indeterminacy; I think that while it might be indeterminate what there is, it necessarily won’t be indeterminate what the range of candidate totalities are, and so I think the maximalist will be able to stop at the determinately existing third-order totality state of affairs and resist infinite regress.

Anyway, I go into all of this in more detail in sections 6 and 7 (and 8 to a lesser degree) of my Truthmaking for Presentists paper. If anyone has any comments on either what’s written here or there, I’d welcome them.

Academics as border police

New rules on overseas students are being introduced by the Government, which will involve academics having to report to the Border Agency when such students have missed a certain number of contact hours. If you are a British citizen or resident and think it is not our role to act as immigration officers, that such rules threaten the autonomy of Universities, that they will make it harder for us to attract overseas students, or that this is generally a Bad Idea, please sign the petition below:

http://petitions.number10.gov.uk/Overseasstudent/

Job: deadline this Friday

Just a last reminder that the deadline for applications for the lecturer or senior lecturer at Leeds (in US terms, roughly equivalent to a tenured assistant or associate prof respectively) is THIS FRIDAY (28th).

For details on how to apply, see the post below.

Leeds job: reminder

Just a reminder that the deadline for the lecturer/senior lecturer position at Leeds is Nov 28th: just over two weeks from the time of posting.

AOS is open over all areas of the department, but we're particularly interested in applicants working in Theoretical Philosophy (broadly construed: so logic, phil logic, phil language, epistemology, metaphysics, phil of maths, phil mind etc) or the history of philosophy.

For the job ad go here (and scroll down a bit).

Schaffer on truthmakers and ontological commitment

In a few places, I've argued that Quine was wrong about ontological commitment. If you want to know what a sentence is ontologically committing to, look not to what the quantifier must range over, say I, but to what must exist to make it true.

Jonathan Schaffer replied in his 'Truthmaker Commitments'. He argues that the motivations for my view are bad ones and goes on to offer some objections to it. He does argue that truthmakers play a role though: but it's not in identifying the ontological commitments, but in identifying what is fundamental according to the theory.

I've just written my reply. I argue that the motivations are good ones, and I aim to counter the objections. I hope the view becomes a bit clearer in my responses to the objections - certainly, they forced me to say some things I hadn't said in the paper Schaffer is criticising. I end, though, by suggesting that it's not obvious there's a genuine dispute between me and Schaffer - that we just mean something different by 'ontological commitment'.

Comments, of course, would be welcome.
Update: the paper has been revised as of 18/10/08

Blind refereeing - request for info

Here's something you don't learn in grad school - probably because it isn't an issue until after you've been publishing for a bit. When submitting a paper, you make it suitable for blind review. Usually, that's really easy: just delete self-references, your name, acknowledgements (well, the latter isn't always done - but I think it should be), etc. But what if you're responding to a paper that is itself responding to you? Do you still need to prepare it for blind review? That would be much more work and might significantly change the tone of the paper, because while you might say things like 'I was unclear: what I meant was . . .' or 'X has misunderstood me' or 'I would respond thus . . .', you would have to hedge everything: 'perhaps Cameron meant . . .', 'Cameron might respond', etc. I'd be interested to hear from people who have experience of writing such replies whether that's what they do or whether they ignore the request to prepare the paper for blind refereeing in such cases (or whether they do something else).

Necessity and triviality

I’ve posted a new draft paper 'Necessary truth, truthmaking and triviality'. The main motivation of the paper is to defend the view that the necessary truths are all and only the trivial truths. A secondary motivation is to argue that, given truthmaker theory, this entails that the necessary truths are exactly the truths that lack a truthmaker.

A sentence is trivially true if and only if its truth makes no demand on the world. That is to say, its truth-conditions are trivially met. Nothing is required of the world for the truth conditions of a trivial truth to be met. Crucially, this is not the same as saying that the world meets the demands that the truth of the sentence imposes on it as a matter of necessity. It is conceptually consistent that the truth of a sentence makes demands on the world that the world necessarily meets. The substantial claim defended in this paper is that there are no such truths: all substantial truths (ones whose truth makes a demand on the world) are contingent.

To make sense of the idea of a truth with trivial truth-conditions, we must have a non-modal understanding of ‘demands’. The demands the truth of a sentence makes on the world can’t simply be what must be the case if the sentence is true. That is independently plausible: even if there are necessary existents such as numbers, or God, we should want an understanding of ‘demands’ such that the truth of ‘Socrates is a philosopher’ demands that Socrates exist and be a philosopher, but not that God or the number 2 exists. Indeed, I argue in the paper that if you only have a modal understanding of ‘demands’ there are a bunch of apparent conceptual possibilities that you simply can’t make sense of. Now if it makes sense that the truth of a sentence not demand that p be the case, even when p is necessary, we can make sense of the idea that the truth of the sentence makes no demands at all.

I argue that such trivial truths must be necessary, lest we violate a very weak version of the principle that truth is grounded in reality (one far weaker than the truthmaker principle). In that case we have an explanation for the necessity of at least some necessary truths: they are necessary because trivial. I further argue that if this is true we should hold that all necessary truths are trivial, lest we admit unexplained necessitites.

This has real consequences for certain debates in metaphysics. It settles the debate over whether there could have been no concrete objects, since ‘there are concrete objects’ is a substantial truth (it demands that there be concreta), hence a contingent one. It motivates, I argue, in favour of states of affairs as opposed to tropes as the truthmakers for contingent intrinsic predications. That is because ‘If the state of affairs of A being F exists, A is F’ is trivially true if true whereas ‘If the particular redness of A exists, A is red’ is substantially true if true (since more is required for A’s existence than that one of A’s properties exist, whereas since A is a constituent of the state of affairs of A being F, the conditions for A’s existence are already met in meeting the conditions for the existence of the state of affairs), and so only the former can be necessary – and given truthmaker necessitarianism, whichever is true is necessarily true.

(I want to give a shout out to Agustin Rayo. I've been much inspired and influenced by his recent work on truth-conditions, ontological commitment, etc. Go to his webpage and read 'On Specifying Truth-Conditions', 'Ontological Commitment' and 'Towards a Trivialist Account of Mathematics'. It's all really excellent stuff, and will give you an idea of the background I'm operating with in this paper.)

Permanent lecturer/senior lecturer at Leeds

Leeds is hiring again. We're seeking to appoint a lecturer or senior lecturer - AOS open, but we'd be especially keen on applicants with AOS in Theoretical Philosophy (broadly construed: i.e. phil logic and language, metaphysics, epistemology, phil mind, etc) or the history of philosophy.

Here's the ad:

University of Leeds

Faculty of Arts

Department of Philosophy


Lectureship/Senior Lectureship in Philosophy

(Available from 1 September 2009)


The Department of Philosophy is one of the largest Philosophy
departments in the UK, with around 30 academic staff and a
large intake of students. In recent evaluations it received a
maximum 24 for Teaching Quality and a rating of 5 in the 2001
Research Assessment Exercise. The Department includes the
Centre for History and Philosophy of Science,
the Centre for Ethics and Metaethics and the Centre for
Metaphysics and Mind.

The ‘Area of Specialisation’ for this position is open
across all areas of the Department but we are particularly
interested in applicants working in the areas of Theoretical
Philosophy (broadly construed) or History of Philosophy.

The position will incorporate undergraduate and postgraduate
teaching, some thesis supervision, and usual non-teaching duties.
With a strong record of research publication, the successful
candidate should be qualified to masters level or equivalent.
A PhD prior to application and teaching experience are strongly
preferred for a Lectureship and are essential for a position at
Senior Lecturer level.

For general information see http://www.philosophy.leeds.ac.uk/

University Grade 7 (£30, 912 - £33,780 p.a.) or University 8
(£34,792 - £41,545 p.a.) or University Grade 9
(£42,791 - £49,606 p.a.)

Informal enquiries to Professor Steven French: S.R.D.French@leeds.ac.uk

To download an application form and job details please visit
www.leeds.ac.uk and click on ‘jobs’.

Job ref 321001  Closing date 28 November 2008

Interviews will take place on 14/15 January 2009

Applicants should submit the completed application form,
full CV, and a writing sample (of no longer than 25 pages)
by the closing date of 28 November.

Vagueness and Naturalness

I've posted a draft of a new short paper on vagueness. I want a view of vagueness that upholds both classical logic and bivalence. I commit, then, to saying that there is a sharp cut-off between the things that satisfy any vague predicate and the things that don't. Williamson secures that by accepting the claim that our usage is fine grained enough for our predicates to latch onto a particular meaning, and that we'd have meant something different had we used the term ever so slightly differently. Like many, I don't find that plausible. Instead, I want to let the other factor that determines meaning do the work: naturalness. The claim I defend is that for any vague predicate there are a bunch of meanings that fit equally well with use, but that one is always the most natural. This is the one we mean, and this determines where the cut-off is: we can't know where the cut-off is because we have no naturalness detector. I explore extending this to arbitrary reference. The idea is that when we say 'Let 'n' be an arbitrary number', 'n' refers to the most natural number. And so on: so I secure bivalence at the cost of some heavy duty metaphysical claims concerning naturalness. It then becomes weighing up the costs and benefits.

But my real view is that the naturalness facts are themselves ontically indeterminate. There is a most natural meaning for 'is bald', but the world hasn't settled which of the candidate meanings is the most natural. In that case, while it is settled that there is a sharp cut-off between the bald and the non-bald things, it is ontically indeterminate where the sharp cut-off is. There is a most natural number that 'n' refers to; but it is ontically indeterminate which one it is.

Comments welcome!

Branching time (x-post from TnT)

I've recently discovered some really interesting papers on how to think about belief in a future with branching time. Folks are interested in branching time as it (putatively) emerges out of "decoherence" in the Everett interpretation of standard Quantum mechanics.

The first paper linked to above is forthcoming in BJPS, by Simon Saunders and David Wallace. In it, they argue for a certain kind of parallel between the semantics for personal fission cases and the semantics most charitably applied to language users in branching time, and argue that this sheds lights on the way that beliefs should behave.

Now, lots of clever people are obviously thinking about this, and I haven't absorbed all the discussion yet. But since it's really cool stuff, and since I've been thinking about related material recently (charity-based metasemantics, fission cases, semantics in branching time) I thought I'd sit down and figure out how things look from my point of view.

I'm sceptical, in fact, whether personal fission itself (and associated de se uncertainty about who one will be) will really help us out here in the way that Saunders and Wallace think. Set aside for now the question of whether faced with a fission case you should feel uncertain which fission-product you will end up as (for discussion of that question, on the assumption that it's indeterminate which of the Lewisian continuing persons is me, see the indeterminate survival paper I just posted up). But suppose that we do get some sense in which, when you're about to fission, you have de se uncertainty about where you'll be, even granted full knowledge of the de dicto facts.

The Saunders-Wallace idea is to try to generalize this de se ignorance as an explanation of the ignorance we'd have if we were placed in a branching universe, and knew what was to happen on every branch. We'd know all the de dicto truths about multiple futures---and we would literally be about to undergo fission, since I'd be causally related in the right kind of ways to multiple person stages in the different futures. So---they claim---ignorance of who I am maps onto ignorance of what I'm about to see next (whether I'm about to see the stuff in the left branch, or in the right). And that explains how we can get ignorance in a branching world, and so lays the groundwork for explaining how we can get a genuine notion of uncertainty/probability/degree of belief off the ground.

I'm a bit worried about the generality of the purported explanation. The basic thought there is that to get a complete story about beliefs in branching universes, we're going to need to justify degrees of beliefs in matters that happen, if at all, long after we would go out of existence. And so it just doesn't seem likely that we're going to get a complete story about uncertainty from consideration of uncertainty about which branch I myself am located within.

To dramatize, consider an instantaneous, omniscient agent. She knows all the de dicto truths about the world (in every future branch) and also exactly where he is located---so no de se ignorance either. But still, this agent might care about other things, and have a certain degree of belief as to whether, e.g. the sea-battle will happen in the future. The kind of degree of belief she has (and any associated "ignorance") can't, I think, be a matter of de se ignorance. And I think, for events that happen if at all in the far future, we're relevantly like the instantaneous omniscient agent.

What else can we do? Well---very speculatively---I think there's some prospect for using the sort of charity-based considerations David Wallace has pointed to in the literature for getting a direct, epistemic account of why we should adopt this or that degree of belief in borderline cases. The idea would be that we *mimimize inaccuracy of our beliefs* by holding true sentences to exactly the right degrees.

A first caveat: this hangs on having the *right* kind of semantic theory in the background. A Thomason-style supervaluationist semantics for the branching future just won't cut it, nor will MacFarlane-style relativistic tweaks. I think one way of generalizing the "multiple utterances" idea of Saunders and Wallace holds out some prospect of doing better---but best of all would be a degree-theoretic semantics.

A second caveat: what I've got (if anything) is epistemic reason for adopting certain kinds of graded attitude. It's not clear to me that we have to think of these graded attitudes as a kind of uncertainty. And it's not so clear why expected utility, as calculated from these attitudes, should be a guide to action. On the other hand, I don't see clearly the argument that they *don't* or *shouldn't* have this pragmatic significance.

So I've written up a little note on some of these issues---the treatment of fission that Saunders-Wallace use, the worries about limitations to the de se defence, and some of the ideas about accuracy-based defences of graded beliefs in a branching world. It's very drafty (far more so than anything I usually put up as work in progress). To some extent it seems like a big blog post, so I thought I'd link to it from here in that spirit. Comments very welcome!

Update: Oh, and worldle abstract:

Indeterminate survival: in draft (x-post from TnT)

Update: I posted this over at Theories and Things, but I feel for it's MV posting I should give the Wordle Abstract for the draft paper:

On with the post:

So, finally, I’ve got another draft prepared. This is a paper focussing on Bernard Williams’ concerns about how to think and feel about indeterminacy in questions of one’s own survival.

Suppose that you know that you know there’s an individual in the future who’s going to get harmed. Should you invest a small amount of money to alleviate the harm? Should you feel anxious about the harm?

Well, obviously if you care about the guy (or just have a modicum of humanity) you probably should. But if it was *you* that was going to suffer the harm, there’d be a particularly distinctive frisson. From a prudential point of view, you’d be compelled to invest minor funds for great benefit. And you really should have that distinctive first-personal phenomenology associated with anxiety on one’s own behalf. Both of these de se attitudes seem important features of our mental life and evaluations.

The puzzle I take from Williams is: are the distinctively first-personal feelings and expectations appropriate in a case where you know that it’s indeterminate whether you survive as the individual who’s going to suffer?

Williams thought that by reflecting on such questions, we could get an argument against account of personal identity that land us with indeterminate cases of survival. I’d like to play the case in a different direction. It seems to me pretty unavoidable that we’ll end up favouring accounts of personal identity that allow for indeterminate cases. So if , when you combine such cases with this or that theory of indeterminacy, you end up saying silly things, I want to take that as a blow to that account of indeterminacy.

It’s not knock-down (what is in philosophy?) but I do think that we can get leverage in this way against rejectionist treatments of indeterminacy, at least as applied to these kind of cases. Rejectionist treatments include those folks who think that characteristic attitudes to borderline cases includes primarily a rejection of the law of excluded middle; and (probably) those folks who think that in such cases we should reject bivalence, even if LEM itself is retained.

In any case, this is definitely something I’m looking for feedback/comments on (particularly on the material on how to think about rational constraints on emotions, which is rather new territory for me). So thoughts very welcome!

Primitivism about indeterminacy: a worry (x-post from TnT)

I’m quite tempted by the view that it is indeterminate that might be one of those fundamental, brute bits of machinery that goes into constructing the world. Imagine, for example, you’re tempted by the thought that in a strong sense the future is “open”, or “unfixed”. Now, maybe one could parlay that into something epistemic (lack of knowledge of what the future is to be), or semantic (indecision over which of the existing branching futures is “the future”) or maybe mere non-existence of the future would capture some of this unfixity thought. But I doubt it. (For discussion of what the openness of the future looks like from this perspective, see Ross and Elizabeth’s forthcoming Phil Studies piece).

The open future is far from the only case you might consider—I go through a range of possible arenas in which one might be friendly to a distinctively metaphysical kind of indeterminacy in this paper—and I think treating “indeterminacy” as a perfectly natural bit of kit is an attractive way to develop that. And, if you’re interested in some further elaboration and defence of this primitivist conception see this piece by Elizabeth and myself—and see also Dave Barnett’s rather different take on a similar idea in a forthcoming piece in AJP (watch out for the terminological clashes–Barnett wants to contrast his view with that of “indeterminists”. I think this is just a different way of deploying the terminology.)

I think everyone should pay more attention to primitivism. It’s a kind of “null” response to the request for an account of indeterminacy—and it’s always interesting to see why the null response is unavailable. I think we’ll learn a lot about what the compulsory questions the a theory of indeterminacy must answer, from seeing what goes wrong when the theory of indeterminacy is as minimal as you can get.

But here I want to try to formulate a certain kind of objection to primitivism about indeterminacy. Something like this has been floating around in the literature—and in conversations!—for a while (Williamson and Field, in particular, are obvious sources for it). I also think the objection if properly formulated would get at something important that lies behind the reaction of people who claim *just not to understand* what a metaphysical conception of indeterminacy would be. (If people know of references where this kind of idea is dealt with explicitly, then I’d be really glad to know about them).

The starting assumption is: saying “it’s an indeterminate case” is a legitimate answer to the query “is that thing red?”. Contrast the following. If someone asks “is that thing red?” and I say: it’s contingent whether it’s red”, then I haven’t made a legitimate conversational move. The information I’ve given is simply irrelevant to it’s actual redness.

So it’s a datum that indeterminacy-answers are in some way relevant to redness (or whatever) questions. And it’s not just that “it is indeterminate whether it is red” has “it is red” buried within it – so does the contingency “answer”, but it is patently irrelevant.

So what sort of relevance does it have? Here’s a brief survey of some answers:

(1) Epistemicist. “It’s indeterminate whether p” has the sort of relevance that answering “I don’t know whether p” has. Obviously it’s not directly relevant to the question of whether p, but at least expresses the inability to give a definitive answer.

(2) Rejectionist (like truth-value gap-ers, inc. certain supervaluationists, and LEM-deniers like Field, intuitionists). Answering “it’s indeterminate” communicates information which, if accepted, should lead you to reject both p, and not-p. So it’s clearly relevant, since it tells the inquirer what their attitudes to p itself should be.

(3) Degree theorist (whether degree-supervaluationist like Lewis, Edgington, or degree-functional person like Smith, Machina, etc). Answering “it’s indeterminate” communicates something like the information that p is half-true. And, at least on suitable elaborations of degree theory, we’ll then now how to shape our credences in p itself: we should have credence 0.5 in p if we have credence 1 that p is half true.

(4) Clarification request. (maybe some contextualists?) “it’s indeterminate that p” conveys that somehow the question is ill-posed, or inappropriate. It’s a way of responding whereby we refuse to answer the question as posed, but invite a reformulation. So we’re asking the person who asked “is it red?” to refine their question to something like “is it scarlet?” or “is it reddish?” or “is it at least not blue?” or “does it have wavelength less than such-and-such?”.

(For a while, I think, it was was indeterminate, one couldn’t know p (think of parallel discussion of “minimal” conceptions ofassumed that every series account of indeterminacy would say that if p vagueness—see Patrick Greenough’s Mind paper). If that was right then (1) would be available to everybody. But I don’t think that that’s at all obvious — and in particular, I don’t think it’s obvious the primitivist would endorse it, and if they did, what grounds they would have for saying so).

There are two readings of the challenge we should pull apart. One is purely descriptive. What kind of relevance does indeterminacy have, on the primitivist view? The second is justificatory: why does it have that relevance? Both are relevant here, but the first is the most important. Consider the parallel case of chance. There we know what, descriptively, we want the relevance of “there’s a 20% chance that p” to be: someone learning this information should, ceteris paribus, fix their credence in p to 0.2. And there’s a real question about whether a metaphysical primitive account of chance can justify that story (that’s Lewis’s objection to a putative primitivist treatment of chance facts).

The justification challenge is important, and how exactly to formulate a reasonable challenge here will be a controversial matter. E.g. maybe route (4), above, might appeal to the primitivist. Fine—but why is that response the thing that indeterminacy-information should prompt? I can see the outlines of a story if e.g. we were contextualists. But I don’t see what the primitivist should say.

But the more pressing concern right now is that for the primitivist about indeterminacy, we don’t as yet have a helpful answer to the descriptive question. So we’re not even yet in a position to start engaging with the justificatory project. This is what I see as the source of some dissatisfaction with primitivism – the sense that as an account it somehow leaves something unimportant explained. Until the theorist has told me something more I’m at a loss about what to do with the information that p is indeterminate

Furthermore, at least in certain applications, one’s options on the descriptive question are constrained. Suppose, for example, that you want to say that the future is indeterminate. But you want to allow that one can rationally have different credences for different future events. So I can be 50/50 on whether the sea battle is going to happen tomorrow, and almost certain I’m not about to quantum tunnel through the floor. Clearly, then, nothing like (2) or (3) is going on, where one can read off strong constraints on strength of belief in p from the information that p is indeterminate. (1) doesn’t look like a terribly good model either—especially if you think we can sometimes have knowledge of future facts.

So if you think that the future is primitively unfixed, indeterminate, etc—and friends of mine do—I think (a) you owe a response to the descriptive challenge; (b) then we can start asking about possible justifications for what you say; (c) your choices for (a) are very constrained.

I want to finish up by addressing one response to the kind of questions I’ve been pressing. I ask: what is the relevance of answering “it’s indeterminate” to first-order questions? How should I alter my beliefs in receipt of the information, what does it tell me about the world or the epistemic state of my informant?

You might be tempted to say that your informant communicates, minimally, that it’s at best indeterminate whether she knows that p. Or you might try claiming that in such circumstances it’s indeterminate whether you *should* believe p (i.e. there’s no fact of the matter as to how you should shape your credences on the question of whether p). Arguably, you can derive these from the determinate truth of certain principles (determinacy, truth as the norm of belief, etc) plus a bit of logic. Now, that sort of thing sounds like progress at first glance – even if it doesn’t lay down a recipe for shaping my beliefs, it does sound like it says something relevant to the question of what to do with the information. But I’m not sure about that it really helps. After all, we could say exactly parallel things with the “contingency answer” to the redness question with which we began. Saying “it’s contingent that p” does entail that it’s contingent at best whether one knows that p, and contingent at best whether one should believe p. But that obviously doesn’t help vindicate contingency-answers to questions of whether p. So it seems that the kind of indeterminacy-involving elaborations just given, while they may be *true*, don’t really say all that much.

Wordles

Via Robbie, I've discovered the genius source of amusement that is Wordle.

Update: Okay, I've become completely addicted. Here are the ones I've saved so far.

Truthmaking for Presentists

The Open Future

Truthmakers and Ontological Commitment

The Contingency of Composition

Turtles All the Way Down

Truthmakers, Realism and Ontology

On The Source Of Necessity

And here is Elizabeth's: Ontic Vagueness

Quantification, Naturalness, Ontology

I’ve posted a draft of a paper ‘Quantification, Naturalness, Ontology’; this is slated for the volume New Waves on Metaphysics, edited by Allan Hazlett – but there’s a while until the deadline, so any comments on it would be really helpful. Here are some of the main themes, on which I’d be grateful to hear thoughts. (These are here condensed and presented without much argument; for further info, obviously, see the paper.)

Thesis 1: As in previous work, I’m concerned with defending a distinction between what there is and what there really is. Following Sider, in order to resist neo-Carnapianism we should insist that there’s a unique most natural existential quantifier: one that carves the world along its quantificational joints. But, there’s no need to say that the ordinary quantifiers of English are this natural quantifier. Naturalness is a reference magnet, to be sure, but it can be trumped by use. But we can introduce a quantifier (‘there really is . . .’) stipulated to be the most natural quantifier. As long as you’re happy with the naturalness talk in the first place, there’s now no mystery in saying that what there is might come apart from what there really is.

Thesis 2: I defend a two-dimensionalist approach to sentences like ‘there is a table’. Considering the universalist world as actual, this sentence requires a table as a truthmaker, and so considering other worlds as counterfactual, we should only judge the sentence to be true at those worlds if they contain certain complex objects, namely tables. But considering the nihilist world as actual, the charitable thing to say is not that that sentence is false but that it requires for its truth only the existence of simples arranged table-wise, and so considering other worlds as counterfactual, we should judge the sentence to be true at a world iff it contains simples arranged table-wise. An attractive consequence is this: assuming (which I hope is the case) that the nihilist world is actual, we have a nice explanation for what many people think is a necessary truth, the necessity of which otherwise looks mysterious, namely: if there are simples arranged table-wise then there is a table.

Thesis 3: It’s right to take Moorean truths about what there is as inviolable. What’s wrong, however, is to read the ontology straightforwardly off of them. The truth of ‘Here is a hand’ is indeed on a stronger footing than any conjunction of premises that entails its falsity. But that doesn’t mean that, e.g., compositional nihilism is false. Compositional nihilism, properly understood, is the claim that no complex objects really exist, and that is compatible with the claim that there are complex objects like hands. The proper methodology is to ask what are needed as the ontological grounds for the Moorean truths. There are no Moorean truths about what there really is.

Thesis 4: The problem of the many is easy. There’s a unique cat on the mat. But asking which collection of particles is the cat, is a bad question. There isn’t really a cat. You can only ask, which collection of particles grounds the fact that there is a cat? Answer: all of them (i.e. all the collections which the universalist thinks are candidates for being the cat). But that doesn’t mean that there are many cats, of course – the one sentence can have multiple grounds.

Thesis 5: Since the ontological commitments of a sentence are its ontological grounds, it’s an open possibility that there are true sentences that lack ontological grounds and hence carry no commitments. I suggest that the truths of mathematics are like this. It’s true that there is a prime number between 8 and 12; but it’s a mistake to think that this is ontologically committing to numbers. (And no ‘paraphrase’ of the sentence into something not quantifying over numbers is necessary to say this.) Mathematical claims are trivial in the sense that they make no demands, a fortiori no ontological demands, on the world. (Cf. what I say here to what Agustin Rayo says in his defence of mathematical trivialism in this excellent paper.)

Thesis 6: Actually not a thesis. I tentatively speculate that one could reduce necessity in the following way: p is necessary iff p lacks an ontological ground. Obviously, not everyone’s going to think this is extensionally adequate, since some think contingent negative existentials lack a ground, and others think everything has a ground, including necessary truths. But I think it looks quite hopeful, and would like to hear whether or not anyone else does.

In other news, Elizabeth and my paper (“Elizabeth and my” – is that right? It sounds terrible, but I can’t think what else it should be.) on the open future has been accepted by Phil Studies. But we’d still appreciate any comments on it, as it’s an issue we’re hopefully going to keep working on.

Metaphysics postdoc at Leeds

Leeds will be hiring a one-year research postdoc in metaphysics (broadly construed) for the academic year 08-09. The post is partially sponsored by the Centre for Metaphysics and Mind.

To apply on line please visit http://www.leeds.ac.uk and click on ‘jobs’, then 'research' (it will be listed as being in the school of humanities, not the department of philosophy). Alternatively, go here. Or application packs are available via email recruitment@admin.leeds.ac.uk or tel+44 (0)113 343 5771. The closing date for applications is August 6th, and interviews will be held in the week beginning Aug 25th.

For US readers: postdocs in the UK are not like in the US. They are a nice gig. There are very minimal teaching or admin duties, so you've basically got a year of research on a decent salary.

Please forward the details on to any potentially interested parties.

PhD studentship in Theoretical Philosophy

PhD studentship available at Leeds: please pass on to any potentially interested parties:

__________________________________
The Department of Philosophy, University of Leeds, intends to offer a Studentship in Theoretical Philosophy to a suitably qualified candidate for its full-time or part-time PhD programme. The studentship is tenable for 3yr (f-t) or 6yr (p-t) from October 2008 and has both tuition and maintenance components: the tuition component will be equivalent to the full EU PhD fee (currently £3.3k p.a. f-t) and the maintenance component will be equivalent to that of the AHRC Doctoral award (currently £12.6k p.a. f-t).The award is conditional on successful application for admission to study for PhD in the Department. However, applicants need not apply for admission prior to application for this studentship. Renewal of the studentship each year is subject to satisfactory progress towards PhD completion.

The successful applicant will undertake a PhD project in the area of Theoretical Philosophy broadly construed and will be supervised by Dr.Robert Williams, Reader in Theoretical Philosophy (http://www.philosophy.leeds.ac.uk/Staff/JRGW/index.html). For a range of preferred research topics, see link there to Dr.Williams' personal home page.

The Department operates a professional training and development scheme for postgraduates: as part of this scheme, successful applicants are often given the opportunity to undertake teaching, which is paid at an hourly rate. The Department also offers its PhD students financial support for conference attendance.

Applications should consist in 6 copies of a CV which includes a 500 word PhD-proposal: applicants should also arrange for 2 academic referees to submit references directly to the Department.

All applications and references should be marked Studentship in Theoretical Philosophy, and addressed to Ms Jenneke Stevens, Postgraduate Secretary, Department of Philosophy, University of Leeds, Leeds LS2 9JT, UK email j.m.stevens@leeds.ac.uk tel 0113 343 3263 fax 0113 343 3265.

Closing date 15 August 2008.

The University of Leeds promotes excellence in teaching, learning and research.

We welcome applications from all sections of the community.

All information is available in alternative formats - please contact 0113 343 5771.

Presentism and Relativity

Familiarly, presentism faces an objection from special relativity. According to special relativity, so the objection goes, there is no such thing as absolute simultaneity: events that are simultaneous according to some reference frame are not simultaneous according to another. As a result, what counts as the present is different from one reference frame to another. If presentism is true, then, what exists must vary from one reference frame to another. But this is uncomfortable. Let us spell this argument out in a bit more detail.

1) There is no such thing as absolute simultaneity. (Premise from special relativity.)
2) Only the present time exists. (Premise from presentism.)
3) Only presently existing things exist, and only presently occurring events are occurring. (From 2.)
4) The present time is the time that includes all and only what is simultaneous with your reading of this . (Analytic of ‘the present time’.)
5) What is simultaneous with this utterance varies from one reference frame to another. (From 1.)
6) What things exist, and what events are occurring, varies from one reference frame to another. (From 3, 4 and 5.)

Presentism looks unacceptable then insofar as special relativity and what we might call ontological absolutism – the claim that what things exist, and what events are occurring, is absolute and not relative to anything; a fortiori it is not relative to a reference frame – are both acceptable.

What does the presentist need to do to meet this objection? A sufficient condition for meeting it, presumably, is that they give some reason for privileging one reference frame over any other; for in that case they can claim simply that what exists is what is simultaneous with your reading of this according to the privileged reference frame. What is simultaneous with your reading of this according to non-privileged reference frames is neither here nor there: there is no pressure to think these things exist unless they are simultaneous with your reading of this according to the unique privileged reference frame.

But how can the presentist have a reason for thinking that one reference frame is privileged (without resorting to claiming that God smiles upon one and not the others)? What could ground the privileged status of one reference frame over another, given that the physical facts don’t appear to distinguish between them?

I hear that question as a question about truthmakers. What we need is a truthmaker for the claim that some reference frame is privileged. If there is some ontological ground for distinguishing one reference frame from the others – some thing or things that mark to pick out one reference frame – then we can, without being arbitrary, take that reference frame to be the privileged one: the one that reveals what there is. So what might the truthmaker be for the fact that some reference frame is the privileged one?

Remember that, for the presentist, to exist is to be present. So consider all the events that exist – they are all and only the presently occurring events. So surely the privileged reference frame is just that one according to which exactly these events are simultaneous. In that case the truthmaker for the fact that this is the privileged reference frame is just what makes it true that those events exist – namely, those events.

So the thought is this. Everyone in this debate agrees that there is a unique set, S, which is the set of the existing entities. (That just follows from the assumption of ontological absolutism, and if you reject that then there is no problem in the first place.) This lets us single out a unique reference frame: the unique reference frame according to which exactly the members of S are simultaneous. And so, if we’ve got good reason to think that everything that exists is present then we’ve got good reason to think that this frame is the privileged reference frame. Since everything in S exists then everything in S is present; so they had better be simultaneous; so the reference frame that says they are simultaneous (and that nothing outwith S is simultaneous with any of them) is obviously the privileged one.

I imagine that seems way too quick. But ask yourself what the demand against the presentist is. It’s not that they must be able to discover what is present. The preceding remarks do not help the presentist do that. It may be in principle impossible for the presentist to know what exists because it is in principle impossible for them to know if their reference frame is the privileged one. But the objection against the presentist wasn’t epistemic, it was ontological. The objection wasn’t that discovering what is present, and hence what exists according to the presentist, is made difficult because there is no absolute simultaneity; the objection was that there is no absolute fact of the matter as to what is present, and hence no absolute fact of the matter as to what exists according to the presentist, because there is no absolute simultaneity. That is what I think is answered by the preceding remarks: insofar as we have reason to think that there is an absolute fact of the matter as to what exists, the presentist has reason to think that there is an absolute fact of the matter as to what is present, since granting the presentist that there is a unique set of existing entities allows them to uniquely specify a reference frame – the reference frame according to which they are all only the present things. What other reference frame could be a candidate for being privileged, given that the presentist thinks that to exist is to be present?

(And the epistemic objection doesn’t seem too worrying to me in any case. It seems to reduce to: you can’t know what exists, because you can’t know if you’re in the privileged reference frame. But why is that any better than any of the myriad sceptical challenges that aim to undermine your knowledge by showing that there are empirically equivalent possibilities where you get it wrong?)

I think the objection against the presentist has seemed more forceful than it is due to the assumption that the presentist should be able to pick out a unique reference frame independently of picking out the class of existing entities. But why hold that assumption? It’s not as if those entities exist in virtue of that reference frame being privileged. If that were the case then it may well be objectionably circular to presuppose their existence in an explanation of why that reference frame is privileged. But existence facts are, plausibly, brute: when it is true that a exists it is true solely in virtue of a. So the existence of the members of S can be taken for granted in any metaphysical explanation we choose to give - indeed, if the truthmaker theorist is right, all explanation comes to a halt when, and only when, we reach propositions concerning what the members of S are.

The members of S don’t exist because they are all present according to the privileged reference frame; rather, it is that reference frame that is privileged because it is the one according to which all and only the members of S are present. All of us, presentist and non-presentist alike, have to simply accept as brute the existence of some entities. For the non-presentist, accepting a set of things whose existence is brute does not serve to privileged one reference frame, but that is precisely because they don’t accept that to exist is to be present. For the presentist, however, these entities must be present, because everything is present, and so it follows immediately that only a reference frame according to which all and only these things are simultaneous is one that gets things right. Since we are sure of at least one thing that it is present – namely the reading of this sentence – and since there is a unique reference frame according to which that event is simultaneous with exactly the members of S, we know that that reference frame is the privileged one.

The argument from relativity might have force against other versions of the A-theory – such as the moving spotlight or growing block views – that postulate a privileged present without saying that what it is to exist is to be present. Such views require a privileged frame of reference but can’t say that it is the frame of reference according to which all the existing things co-exist: that frame of reference would get things wrong since both views admit the existence of past entities as well as present ones. And so they need another answer as to what grounds the privileged status of the reference frame that gets things right, and it’s not clear what they can say. But presentism, I think, faces no problem: and so this is one reason to think that presentism is the best version of the A-theory available.