Presentist counting

In a posthumous paper, David Lewis shows that one can find a presentist paraphrase of sentences like "There have ever been, are or ever will be n Fs" for any finite n. But his method doesn't work for infinite counting.

It turns out that there is a solution that works for finite and infinite counts, using a bit of set theory. For any set S of times, say that an object x exactly occupies S provided that at every time in S it was, is or will be the case that x exists and at no time outside of S it was, is or will be the case that x exists. For any non-empty set S of times, let n_F(S) be a cardinality such that at every time t in S it was, is or will be the case that there are exactly n_F(S) objects exactly occupying S. This is a presentist-friendly definition. Let N be any set of abstracta with cardinality n_F(S) (e.g., if we have the Axiom of Choice, we should have an ordinal of that cardinality) and let e_F(S) be the set of ordered pairs { <S,x> : x∈N }. We can think of the members of e_F(S) as the ersatz Fs exactly occupying S. Let e_F be the union of all the e_F(S) as S ranges over all subsets of times. (It's quite possible that I'm using the Axiom of Choice in the above constructions.) Then "There have ever been, are or ever will be n Fs" can be given the truth condition |e_F|=n.

This ersatzist construction suggests a general way in which presentists can talk of ersatz past, present or future objects. For instance, "There were, are or ever will be more Fs than Gs" gets the truth condition: |e_G|≤|e_F|. "Most Fs that have ever been, are or will be were, are or will be Gs" gets the truth condition |e_FG|>(1/2)|e_F|, where FG is the conjunction of F with G. I don't know just how much can be paraphrased in such ways, but I think quite a lot. Consequently, just as I think the B-theory can't be rejected on linguistic grounds, it's going to be hard to reject presentism on linguistic grounds.

Another Philosophy Jobs Site: PhilJobs

We had none, now we have two and they are both amazing!!! Open-access philosophy job listings, that is. Alongside Phylo Jobs (check out the new features, btw!), now we have PhilJobs (courtesy of David Bourget and David Chalmers).
The next step now is to replace first-round interviews at the Eastern with either Skype interviews or straight on campus interviews and the dysfunctional APA will have be made completely irrelevant.

New Philosophy Jobs Site!

Wonderful news for job seekers and search committees via The Philosophy Smoker:

Chris Sula and [David Morrow] have revamped the Phylo site to create an actual jobs board to (ahem) supplement the JFP. The URL is the same as the old wiki: http://phylo.info/jobs. As of today, we’ll start accepting job postings in that space from departmental representatives only. Following Harry Brighouse’s advice, we’ll also require a link to an external site (e.g., an announcement on the department’s web site) to verify each post’s authenticity. We’re moving the job wiki to http://phylo.info/jobs/wiki. People will still be able to post unofficial updates there. We’re still in the process of updating the wiki software to play nicely with the jobs board, but it will be up well before anyone needs to post status updates. In the meantime, watch the main jobs board to find out about job openings.

A paradox concerning propositions

Propositions generally seem to be about things. The proposition that Tibbles is on the mat is about Tibbles and a mat. The proposition that 2+2=4 is about some numbers. The proposition that chips are on the counter is about chips and a counter. And so on.

Some propositions (statements, sentences, beliefs, etc.) are intuitively about themselves. For example, the proposition that all propositions merit investigation is intuitively about itself.

Now for a paradox. Consider the following proposition P: every proposition that is not about itself is mundane.

P is paradoxical because it seems to be about itself if and only if it is not. Let me draw this out. Suppose first that P is about itself. Then we can show that P is not about itself as follows. P is about all and only those propositions that are not about themselves, for it says that each is mundane. So, P is not about any proposition that is about itself. Therefore, P is not about P if P is indeed a proposition that is about itself. Therefore, P is not about itself if it is about itself. Suppose, on the other hand, that P is not about itself. We have already observed that P is about those propositions that are not about themselves (because P reports that each is mundane). Therefore, if P is one of those propositions that aren't about themselves, then P is about P. So, either way, we fall into contradiction.

We can make the paradox more acute by stipulating that 'x is about y' means 'x quantifies over instances of a kind of which y is an instance'. We can then ask whether or not P is about P in that precise sense. (If you think you see a way out of the paradox, ask yourself if there's a way to re-write the paradox that avoids your solution, and I'm guessing you'll see that there is.)

This paradox will remind you of Russell's paradox concerning the set of all sets that aren't members of themselves. But I believe the paradox of propositions is much harder to solve. Concerning sets, we can, if we like, treat "set" talk as plural reference talk (thereby eliminating the existence of sets altogether), or else we may carefully craft axioms of sethood (such as ZFC) that preclude the existence of sets that are members of themselves.

But such solutions are not nearly as promising when it comes to propositions. If you think we can simply eliminate propositions, then run the paradox in terms of sentence tokens: the sentence token represented by P surely exists (or at least there are things arranged P-wise...). We might try to craft axioms of aboutness to get out of this, but such axioms won't take away the deep feeling that P should be about itself if and only if it is not. (With sets, by contrast, there is something right about supposing that no sets contain themselves.) So, we have a paradox on our hands that appears to be more serious than previous ones of its kind.

The paradox could perhaps be viewed as evidence against the reliability of our a priori faculties (though, of course, we'd have to rely on those same faculties to "see" this!) Or, more drastically, someone could view it as evidence that reality is at bottom absurd. I think it should be viewed as an invitation to gain a deeper understanding of the nature of propositions and aboutness.

Suggested ways of resolving the paradox are welcome. (I have a solution, but before I share it, I'd like to see how others might solve the problem.)

Brian Leiter Caves in to Pressure from the Continental Lobby: Metaphysicians Should Boycott Leiter Report :-)

For the interpretationally challenged, the title of this post is a joke (hence the smiley). For those who haven't followed the Synthese affair, the title paraphrases the one of this other post. In any case, readers of this blog may want to spoil the fun by voting en masse here for 'Should be mandatory' and and for 'Every department should have the subject as its central focus'. (Since this is not supposed to be a serious poll, I would even think you could vote multiple times from multiple locations if you are so inclined and have a lot of time in your hands)

Special Relativity and Perdurantism

There seems to be a problem for the conjunction of Special Relativity and perdurantism. Maybe this is a standard problem that has a standard solution?

Let's say that being bent is an intrinsic property. Perdurantists of the sort I am interested in think that Socrates is bent at a time in virtue of an instantaneous temporal part of him being bent (I think the argument can be made to work with thin but not instantaneous parts, but it's a little more complicated). Therefore:

1. x is bent at t only if the temporal part of x at t is bent simpliciter.

The following also seems like something perdurantists should say:

2. x is bent simpliciter only if every temporal part of x is bent simpliciter.

Now, we need to add some premises about the interaction of Special Relativity and time.

3. There is a one-to-one correspondence between times and maximal spacelike hypersurfaces such that one exists at a time if and only if one at least partly occupies the corresponding hypersurface.

Given a time t, let H(t) be the corresponding maximal spacelike hypersurface. And if h is a maximal spacelike hypersurface, then let T(h) be the corresponding time. Write P(x,t) for the temporal part of x at t. Then:

4. P(x,t) is wholly contained within H(t) and if z is a spacetime point in H(t) and within x, then z is within P(x,t)

and, plausibly:

5. If a point within x is within a maximal spacelike hypersurface h, then P(x,T(h)) exists.

Now suppose we have Special Relativity, so we're in a Minkowski spacetime. Then:

6. For any point z in spacetime, there are three maximal spacelike hypersurfaces h₁, h₂ and h₃ whose intersection contains no points other than z.

Add this obvious premise:

7. No object wholly contained within a single spacetime point is bent simpliciter.

Finally, for a reductio, suppose:

8. x is an object that is bent at t.

Choose a point z within P(x,t) and choose three spacelike hypersurfaces h₁, h₂ and h₃ whose intersection contains z and only z (by 6). Now define the following sequence of objects, which exist by 4 and 5:

• x₁=P(x,t)
• x₂=P(x₁,T(h₁))
• x₃=P(x₂,T(h₂))
• x₄=P(x₃,T(h₃))

Observe that x₄ is wholly contained in the intersection of the three hypersurfaces h₁, h₂ and h₃, and hence:

9. x₄ is wholly at z.
10. It is not the case that x₄ is bent simpliciter.

Now:

11. x₁ is bent simpliciter. (By 1 and 8)
12. x₂ is bent simpliciter. (By 2 and 11)
13. x₃ is bent simpliciter. (By 2 and 12)
14. x₄ is bent simpliciter. (By 2 and 13)

Since 14 contradicts 10, we have a problem. It seems the perdurantist cannot have any objects that are bent at any time in a Minkowski spacetime. This is a problem for the perdurantist.

If I were a perdurantist, I'd deny 2, and maintain that an object can be bent simpliciter despite having temporal parts that are bent and temporal parts that are not bent. But I would not be comfortable with maintaining this. I would take this to increase the cost of perdurantism.

What is ironic here is that it is often thought that endurantism is what has trouble with Relativity.

One-Category Abundant Platonism

Standard Abundant Platonism (SAP) holds that to every predicate there corresponds a property, and items satisfy the predicate if and only if they exemplify the property.  Moreover, it holds that exemplifiers are not explanatorily prior to what they exemplify.  Normally, we think of SAP as a two-category theory: individuals and properties.

But here is a suspicion I have.  Little if any explanatory work is being done by the distinction between individuals and properties.  The serious explanatory work is all being done by the relation of exemplification.  Here are two examples.

1. Standard Platonists say that x and y are exactly alike in some respect if and only if there is some property P such that x exemplifies P and y exemplifies P.  But drop the word "property" from the previous sentence, and we have an account of exact alikeness that is even better: x and y are exactly alike in some respect if and only if there is a z such that x exemplifies z and y exemplifies z.  This is extensionally just as good, but simpler. (One can do more complex stuff about determinates and determinables to get resemblance in some specific respect, but again that doesn't need the concept of property, just the relation of being a determinable of.)

2. Standard Platonists say that to each predicate F there corresponds a property Fness, and that x is F if and only if, and if so because, x exemplifies Fness (we should probably have an exception to the "because" clause when Fness is exemplification).  But change "there corresponds a property Fness" to "there corresponds an entity Fness", and this works just as well as an account of predication.


Besides, the concepts of "individual" and "property" are foggy.  (We might try to say: "x is an individual if and only if x cannot be exemplified."  But that doesn't work for abundant Platonism, as abundant Platonism will have properties like being a square circle.)

So, if you're going to be a Platonist, why be a two-category abundant Platonist?  Why not be a one-category abundant Platonist instead?