Wednesday, July 25, 2007

The Truth Conditions of Tensed Propositions

I am an A-theorist with respect to the metaphysics of time. An A-theorist is one who believes that there is an objective 'now' or, what amounts to the same thing, that the totality of reality undergoes change. The opposite of the A-theory of time is called the B-theory. According to the B-theory, reality is constant and unchanging. There may be temporal relations between different parts of reality, but reality itself, taken as a whole, is a static block.

There are several reasons why I'm an A-theorist despite the fact that the B-theory is the philosophical fashion nowadays. One argument in particular that seems persuasive to me is this one:
  1. There are true tensed propositions.
  2. If there are true tensed propositions then there are tensed facts that make those propositions true.
  3. Therefore, there are tensed facts. (from 1 and 2)
  4. If there are tensed facts then there is an objective 'now'.
  5. Therefore, there is an objective 'now'. (from 3 and 4)
Needless to say, this argument is controversial, especially premise 2. Premise 4 is a platitude, a straightforward consequence of the notion of a 'tensed fact'. (The notion of tense has to do with the relation of things to the present or 'now'.)

Premise 1 has been denied by many B-theorists. Bertrand Russell, Willard Quine, and others argued that there are no tensed propositions. The justification for this claim was supposed to lie in the fact that all tensed propositions could be translated salve significatione (without loss of meaning) into tenseless propositions. If that were true, then tense could be safely eliminated.

But during the 1970's and 1980's, in large measure as a result of the work of Richard Gale, B-theorists generally abandoned this strategy. The problem, which Gale and others pointed out, is that tense conveys meaning. For example, it is quite a different thing to be told "A bomb is about to go off (future tense) in the UNLV philosophy department" and "A bomb goes off (tenseless) in the UNLV philosophy department". The former tells me that the bomb has not yet gone off but soon will. (So maybe I should run for cover.) But the latter tells me nothing as to whether the bomb's going off is in the distant past, recent past, present, near future, or distant future. It can't guide my action in the same way because it contains less information. So, pace Russell et al., tense cannot be eliminated without loss of meaning.

Another way to deny Premise 1 is to concede that there are tensed propositions, but deny that any of them are true. I don't know of anyone who has defended this position, but it is a theoretical possibility. One problem with it is that is flies in the face of commonsense. Every natural language known to us has a system of tenses, and speakers of those languages routinely make tensed claims, and many of these claims would be regarded by other competent speakers of those languages as true. Thus, "The Allies won (past tense) WWII" is true; "George W. Bush is (present tense) the President of the U.S." is true; and "The sun will shine (future tense) on the Earth tomorrow" is true. It takes quite a bit of sophistication (sophistry?) to evade the force of commonsense on this point.

Today, the target of choice for nearly all B-theorists is Premise 2. Proponents of the so-called "new" B-theory of time concede that there are true tensed propositions and that they cannot be translated salva significatione into tenseless propositions, but they deny that there have to be tensed facts to make these propositions true. They argue, in other words, that tensed propositions have purely tenseless truth conditions. There are different versions of this strategy (e.g., the "date theory" and the "token-reflexive theory"), but all of them are variations on the same two-part strategy. Given a generic tensed proposition like "It (was, is, will be) the case that E, we generate tenseless truth conditions by
  • replacing 'was', 'is', and 'will be' with relations like 'earlier than', 'simultaneous with', and 'later than', respectively
  • specifying as the relata of those relations (i) the event spoken of, E, and (ii) a designated time, e.g., this date, the time of this utterance, etc.
For example, on this view, the truth conditions of "Caesar was assassinated" may be given as follows: "Caesar is (tenseless) assassinated earlier than 07/25/2007."

For my part, I don't think this strategy works. (B-theorists, of course, will beg to differ.) As I see it, to claim that "Caesar was assassinated" is to claim that this event has already happened, that it is past. But a claim is true if and only if what is claimed to obtain does obtain. Since the claim is that this event is past, it is true if and only if the event is past. It's being 'earlier than' some date, whether specified referentially (e.g., 07/25/2007) or token-reflexively (e.g., "the time of this utterance"), is not enough, for in neither case does it require the event to be past, as claimed.

Let me put this another way. Because "Caesar is (tenseless) assassinated earlier than 07/25/2007" is tenseless it gives us no information about whether 07/25/2007 is past, present, or future. As I am writing this, I know that that date has just recently become past. But that knowledge comes from outside the tenseless proposition. In and of itself, the tenseless proposition is perfectly compatible with any of three differently tensed propositions:
  • Caesar was assassinated.
  • Caesar is being assassinated.
  • Caesar will be assassinated.
If satisfying the tenseless truth conditions suffices for the truth of the first tensed proposition then, by reasons of parity, it should also suffice for the truth of the other two and thus of all three. But it can't. These tensed propositions are mutually incompatible. So satisfying tenseless truth conditions cannot suffice for the truth of any tensed proposition.


At 7/26/2007 2:58 PM, Blogger David said...

Hi, Alan.

I consider myself to be a sympathetic A-theorist.

However, couldn’t the B-theorist define the present by using a self-reflexive indexical (something like ‘all points along the temporal axis that have a zero metric with respect to me’)?

The ‘past’ is all points along the temporal axis ‘earlier than’ now, as defined.

I guess this makes the speaker/observer the truth maker for tensed statements. Is there something wrong with this move?

At 7/26/2007 3:59 PM, Blogger Alan Rhoda said...

Hi David,

Your suggestion is intriguing, though I doubt it works. When you speak of having a zero metric "with respect to me", I want to know which "me". Me-at-t1? Me-at-t2? Me-at-t3?

I think the best the B-theorist can do is to drop the notions of 'past', 'present', and 'future' entirely and replace them with the notions of 'relative past', 'relative present', and 'relative future', respectively. Thus, if t1 is earlier than t2, then t1 is past relative to t2, and t2 is future relative to t1.

But doesn't dropping the notions of 'past', 'present', and 'future' amounts to the same thing as denying that there are any genuinely tensed propositions?

At 7/26/2007 11:07 PM, Blogger David said...

The relevant me time-slice would be the one who said 'in the past', 'now' or 'in the future'. Just as, if I say, 'I am tired' the relevant time-slice being indicated as tired would be the one who said the words.

At 7/30/2007 9:24 PM, Blogger Alan Rhoda said...

Hi David,

I follow you. But I think your proposal on behalf of the B-theorist amounts to the same thing as replacing 'is past' with 'is earlier than', 'is present' with 'is simultaneous with', and 'is future' with 'is subsequent to'.

That move, I submit, is tantamount to denying that there are any true tensed propositions. For a proposition to be tensed, it has to refer to the past, present, or future as such.

At 7/30/2007 10:44 PM, Blogger Ian said...

I think your argument, to work in favor of the A-theory, would have to be revised a bit. As a B-theorist, I could actually agree with every statement you list, including premises 2 and 3 and your conclusion, 5. I would just interpret them very differently from you. I do believe that there is an objective now. Since my writing of 'now' occurs at 10:29PM 7/30/07 then my 'now' here refers to 10:29PM (PST) 7/30/07 and since I believe that there is an objective 10:29PM (PST) 7/30/07, I can perfectly agree that there is an objective now. The reference of 'objective now' will simply change depending on the time its uttered. And I can perfectly well, in the same way, accept that there are tensed facts. Of course it's a fact that my writing this is present. But what I deny is that this is some fact that's distinct from or more primitive than the fact that this writing is taking place at the B-series position it's at (or some other combination of tenseless facts). After all, a B-theorist need not be an eliminativist about tense - reductivist positions are readily available.

That's why to insist that "Since the claim is that this event is past, it is true if and only if the event is past." is all by itself, without further argument, not enough to get you to the conclusion that "It's being 'earlier than' some date, whether specified referentially (e.g., 07/25/2007) or token-reflexively (e.g., "the time of this utterance"), is not enough, for in neither case does it require the event to be past, as claimed." Otherwise, someone could use the same sort of reasoning to "prove" that there must be a single, absolute privileged, irreducibly "here" place that we all refer to when we say "here". But that's just crazy. All the phenomena you mention of being able to know that X is present but not the time of X is perfectly paralleled in other cases where what's involved is a case of the "essential indexical". Knowing that X is in my apartment is not enough to know that X is here, but that doesn't show that X being here is anything over and above its being in my apartment. There is no single, absolute privileged, irreducibly "here" place that we all refer to when we say "here". So I can't see how these sorts of considerations listed in this post give any sort of good evidence for a tensed view without some heavy duty arguments to establish why they show that there are extra weird facts in one case (time) but not in another (place).

As for people denying 1 and yet thinking that there are tensed propositions (they're just all false) - I assume this is what you're talking about when you said "Another way to deny Premise 1 is to concede that there are tensed propositions, but no ones." - there actually is at least one person who I think does this. Nathan Oaklander thinks that tensed assertions are literally false but pragmatically useful.

Hopefully that's all reasonably comprehensible as it's late and I've just come back from a long vacation!

At 7/31/2007 1:27 AM, Blogger Alan Rhoda said...

Hi Ian,

Thanks for your comments. I'll be sure to give them some thought, especially the time-space parallel that you bring up.

Thanks also for the point about Oaklander. I didn't know that was his position.

As for your claim that a B-theorist could accept all of my premises and my conclusion, I think that's just playing games with words. By an 'objective now' is meant that there is a moment that is uniquely present. For the B-theorist, no moment is uniquely present, except in the utterly trivial sense that it's the only moment simultaneous with that very moment itself.

At 7/31/2007 9:14 AM, Blogger Ian said...

Well, if you are stipulating that "objective now" means what the A-theorist means when he says it, then of course the B-theorist can't agree to it in that sense. If that's the case, you are correct. But if, on the other hand, one has a B-theory of language and doesn't already treat "objective now" as a theoretical term defined in an A-theoretic sense then the B-semantics are going to come out so that a token of "objective now" refers to the time of its tokening. This is all I meant to be saying. If that's just playing game with words, then I don't see anything wrong with it since the A-theorist tries to give semantics for ordinary pieces of language just as much as the B-theorist does.


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