Monday, May 31, 2010

A simple argument against presentism

  1. (Premise) Only an actually existing event can be seen.
  2. (Premise) A wholly past event can be seen.
  3. Therefore, a wholly past event can be actually existing.
  4. (Premise) If presentism is true, a wholly past event cannot actually exist.
  5. Therefore, presentism is not true.
A simple example for (2): If the moon were to almost instantaneously change color all over, we could see (without any instruments) the event of this change. But we'd see the event about one second after it happened (only relative to our reference frame, but in any case the presentist has no room for such a relativity).

One might want to make the stronger claim that all the events we perceive are past. I don't know if that's true. Maybe we can have direct perception of the future. Maybe a tennis player's noninferential predictions of future ball positions are like that. Moreover, even if that were true, the presentist only says that no wholly past event is actual. Many of the events we perceive are both past and present—we can only see them because they are in part past, but they are still going, and hence in the future.

35 comments:

Yave said...

The presentist could very easily reject premise 2. For example, one could say that it simply isn't the case that a wholly past event can be seen. I don't see the moon (much less the moon as it was a second ago), I only see (present) light reflected by the moon. The properties of the light allow me to infer what the moon was like 1 second ago.

Drew said...

I'll agree with that. If this argument is to go through, you've got to give more support for premise 2.

Also, could you explain premise 1 in more detail? What does it mean for an actually existing event to be seen? And what is meant by seen?

Alexander R Pruss said...

I look at my hand. What do I see? A hand. That's what we say: we see hands, dogs, jumps, changes of color, etc. Normally we don't see light. (An exception is when you see a beam of light at night or in a dusty room.)

Now, we have a very good scientific theory according to which we see by means of light, and our brain processes retinal stimulations in such a way as to lead to the perception. But the perception is still not of the light or of the retinal stimulation, but of a hand, or a dog, vel caetera.

Now, maybe the presentist could deny this common sense understanding of seeing, deny that she has ever seen any people, or clouds, or flowers, and so on. That, I think, is badly mistaken. But my point remains. Suppose what I see is the photons from the moon. Well, by the time my brain has processed the data, the photons that allegedly I see have already been absorbed by my rods and cones. So if presentism is true, and one has this theory of perception, I end up seeing nonexistent photons. And just as I don't see nonexistent events, so too I don't see nonexistent objects.

Andrew said...

I think externalism is very plausible. Unless you want to say perception is merely internal phenomena, I think we are going to want to say that we perceive/see the moon.
To deny premise 2 would seem to commit one to holding that perception is internal as opposed to a relation with an external object. Granted, this is an option, but I think a VERY bad one. I think premise 2 is true, for similar reason why i think externalism (in various areas) is true.

Alexander R Pruss said...

A standard observation is that when someone is undergoing a visual illusion, we like to use "seem to see". "See" is factive, like "know".

Drew said...

We also say: The store is five minutes north. If your wife told you that and you started questioning her statement with that kind of analytical, hairsplitting logic, I don't think she would be too impressed.

Alexander R Pruss said...

I thought that the hairsplitters were those who insisted that we didn't see the moon, but only saw light from it. :-)

David Gawthorne said...

As a presentist, I intuitively want to reject premise 1.

If perception requires a causal connection then this argument is just a variant of the usual problem for presentists relating to causal relations across times, often dealt with by recourse to the representational properties of abstracta or to possible worlds.

Alexander R Pruss said...

I'd rather say that the argument relies on the phenomenology of seeing than that it relies on causation.

David Gawthorne said...

Then why wouldn't I just reject 1?

Alexander R Pruss said...

Maybe because of the awkwardness of saying "I am seeing a non-actual event, but my perception is fully veridical"?

David Gawthorne said...

That's pretty mild awkwardness. What about the awkwardness of, 'I'm seeing something that is no longer there.' ? [Quantifiers restricted to the present if you like]

David Gawthorne said...

Ignore that last botched bit about quantifiers. The point is that it is true for any theory of time, but it's awkward.

Alexander R Pruss said...

It's unproblematic to hear things that aren't there any more, say when we hear a rock slide crashing down in the distance, a couple of seconds after we've already seen it. But it does seem problematic to hear things that aren't real, and yet for it to be veridical.

But if you're not made uncomfortable, I guess this argument isn't for you. Don't worry, there are others. :-)

David Gawthorne said...

Tell me about it. STR is a pickle.

Alexander R Pruss said...

I should add that part of my motivation here is that presentism often presents itself as common sense. But I think 1 is pretty commonsensical. :-)

With STR, I think the presentist should just bite the bullet: there is a preferred reference frame, even if we can't empirically know what it is.

Jarrett said...

I think a presentist could say, sure a wholly past event can be seen, but not that a wholly actual past event can be seen. Though you say a presentist can’t hold this type of relativity.

To emphasize Yave’s comment even more, for example, when astronomers looked into deep space and saw (notice I’m using past tense, lol) SN 1987A, which is a supernova that happened 168,000 years prior to its observation in 1987. We don’t say the supernova (the event) happened/occurred in 1987, even though this is when we first noticed that the event took place. So, even though the supernova was seen, it was no longer actual(lized) when it was observed in 1987. Though, once again, you say a presentist has no room for such a relativity.

However, if we really want to split hairs, and I do, I believe we never sense the ‘true’ present, since it takes our brains just a split second for us to compute all of the sensory data that is required for us to make sense of our external world.

Also, I have a question about the eternalist view (I don‘t know if you hold this position). Doesn’t this view succumb to the problem of arguments against actual infinites? Maybe one can opt out and say the future isn’t eternal, but if one is a theist and/or believes in immortality/afterlife, like you and I do, than doesn’t the problem of actual infinities come back, on the eternalist view?

Drew said...

Jarrett. You beat me to the punch. I was just about to use the supernova argument.

And Dr. Pruss admitted that eternalism runs into the problem of actual infinites and the whole Grim Reaper paradox. Presentism, on the other hand, will never actualize an infinite number of events.

Alexander R Pruss said...

There are only two kinds of problems of actual infinity that bother me:
1. Grim Reaper type situations.
2. Probabilistic epistemic paradoxes.

In regard to 1, the problem is only when there is a time t such that there is an actually infinite number of things prior to t. So it's not a problem with an actual infinite per se, as with a simultaneous or past infinite. An actual infinite strung out futurewise does not allow one to generate a Grim Reaper paradox.

In regard to 2, the probabilistic epistemic paradox that worries me is worst in the case where some time has an infinite number of things past or simultaneous with it. I have some worries about an infinite strung out futurewise, but those worries seem independent of whether the futurewise infinity is actual or not.

So, in summary, a futurewise infinity is not a problem in regard to 1, and in regard to 2, it doesn't matter whether it's an infinity of actual events or not.

bernardz said...

Although others have said this, please let me note Alex under Einstein relativity, the moon one second later is the observers frame of reference. It is not the observers past.

Alexander R Pruss said...

Yeah, but the presentist can't make that distinction, I think.

Also, it may not be one second in the past, but it could still be somewhat in the past, since once the light hits the eye, data from the retina moves to the brain at less than the speed of light. Actually, then, there is no need to bring in the moon--any event that happens over a short enough period of time will be like that.

Jonathan D. Jacobs said...

The conclusion says that a wholly past event "can be actually existing." But "actually" sounds to my ears like a modal operator, not a tense operator. And "be existing" begs for temporal clarification. The options seem to be:

3a. An actual, wholly past event can exist now.
3b. An actual, wholly past even can have existed.

But 3b is not problematic to the presentist, so the argument needs 3a. But in order to get 3a, premise 1 needs to be changed to:

1a. Only an actual event that exists now can be seen.

But everyone should deny 1a.

Alexander R Pruss said...

Well, replace "actually existing" with "real" or "in the scope of quantifiers". :-) I.e., whatever it is that presentist thinks past events aren't. (Unless the presentist simply thinks past events aren't present, which every A-theorist agrees on absolutely, and every B-theorist agrees on though perhaps on a different understanding.)

Joshua Rasmussen said...

I'd like to call into question premise 4.

We may distinguish between

(1) e presently exists

and

(2) e is present

Similarly, we may distinguish between

(3) e exists -- wholly in the past

and

(4) e is wholly past

I'm inclined to think that there are events that "are wholly past"--i.e., they have the property of having had obtained and not presently obtaining.

But I don't think that there are any events that exist-over-there-in-the-past.

Presentism: it's always true that everything that exists, exists now. I think it's consistent with presentism that some presently existing things have the property of having obtained. Such things are "wholly past" events.

Joshua Rasmussen said...

So, the event of the moon changing color exists--indeed always exists. But if we see that event it's likely because it (presently) has the property of having recently OBTAINED.

Alexander R Pruss said...

That's not a standard presentism. On standard presentism, events exist only when they occur. On the happy side, this view solves a good deal of the grounding problem with standard presentism.

But perhaps by "events" you mean abstract entities that exist necessarily?

Joshua Rasmussen said...

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Sure--maybe "Chisholm events". :)

I think it's a standard version of ersatz presentism. It shouldn't surprise you that the best version of presentism resembles eternalism in salient respects. :)

Alexander R Pruss said...

But it's not abstract entities that we see.

enigMan said...

presentism often presents itself as common sense. But I think 1 is pretty commonsensical

Presentism is common sense. (If something is said to exist we would not usually think that it might not yet exist or that it no longer exists.) But common sense doesn't tell us that we can only see current events. We can see past events on the TV. And we can see objects.

Moving on from common sense, we may say that we are only seeing photons when we look at the TV. But that's probably false. We don't see the photons, we see by the photons (if photons exist).

And this sort of linguistic behaviour is exhibited by talk of things other than time. E.g. I look at your face and see dust that has yet to fall but I think that you can be seen. (Or to combine the two, I hear a vibration of the air made to a pattern extracted from other vibrations made by you and I think that I can hear you speaking.)

Alexander R Pruss said...

"If something is said to exist we would not usually think that it might not yet exist or that it no longer exists."

I think this may be an artifact of using a tensed language in which what does duty for an eternal tense is a present tense.

enigMan said...

But if we have such a tensed language because that's most compatible with common sense, then presentism is still common sense. And if you look around you, at what exists, there are most obviously tables and chairs, trees and cars, cats and dogs, and so forth. In that common sense context, dinosaurs no longer exist, and when they did, tables and chairs had yet to exist. And a tenseless approach is counter-intuitive when it comes to such ordinary objects. E.g. if I move my chair, I'm moving the whole of it, not some (temporal) part of it.

Anyway, I don't think that common sense tells us that we can only see things that exist. We can see ghosts (or fictional characters on the TV) even if they don't exist. We can see things that aren't there, according to common sense. When we think about it, we may concede that we didn't really see the thing that wasn't there. But when we think about it, we see that we can hear things that no longer exist (e.g. the lightning that's no longer there). And so we can see that, while we don't really see an actual ghost (or Sherlock Holmes), we can see things that no longer exist. Such thoughts are quite common.

enigMan said...

Incidentally, I have some qualms about your use of the actuality operator in your premises. If actuality is contrasted with possibility, then Sherlock Holmes actually exists, as a fictional character. By contrast, the hero of the story that I've not yet got around to writing only possibly exists, as a fictional character. So my qualm is that if presentism is true, then a wholly past event can actually exist, as a historical event. It no longer exists in the simple sense, just as Sherlock Holmes does not exist. But it exists in the past, even under Presentism, insofar as that just means that it did exist, just as Sherlock Holmes exists in Conan Doyle's stories. Your problem, as I see it, is that existence in the simple sense is either so general that it includes not only existence at other times but also existence in stories, or else it is not automatically eternal (is most naturally tensed), which is why you need something like an actuality operator.

Alexander R Pruss said...

Suppose I tell you a bald-faced lie about Baruch Jones, a really smart detective, who told me that the Dean of Humanities at University of Southeast Alaska is stealing from petty cash. My assertion that Jones existed was a lie, and Jones doesn't exist.

Now, suppose instead of asserting this as a bald-faced lie, I tell it to you as a fiction. Then Baruch Jones, on your view, actually exists.

I think this is implausible. Imagine some intermediate cases. Suppose I assert the lie about Baruch Jones, but you misunderstand me to be telling you a bit of fiction. Does Jones exist then? Or suppose that I've lost track of the distinction between lies and fictions.

Or suppose that I tell you the story within the scope of a "Consider the following propositions" operator. At this point Baruch Jones doesn't exist. Now I have a choice. I can tell you:
a. These propositions are false.
b. These propositions are true.
c. These propositions are a fiction.
Clearly in cases a and b, Baruch Jones still doesn't exist. But in case c, it seems he does, if there are fictional characters. After all, why should the order of story exposition matter? But it seems really weird that an entity, a fictional character, comes into existence as soon as I utter c.


All in all, the idea that fictional characters exist strikes me as very implausible.

Alexander R Pruss said...

Also, there is no entity without identity. But there need be no fact of the matter whether fictional character x is identical with fictional character y. The text might simply underdetermine it. Perhaps the text contains an unsolved mystery, and one solution is that x=y, but the text doesn't come out one way or another about it--some of the characters speculate that x=y and some speculate that not.

enigMan said...

But I agree with you that it's implausible that if Jones is fictional then Jones exists. My point is that it's no less implausible that if Jones was one of an extinct species of mere animals then Jones exists.

Nevertheless there are fictional characters. Sherlock Holmes is a fictional character, for instance. Your argument from indeterminacy, by contrast, is rather suspect. I take a Moorean stance on such matters, and so does common sense. E.g. chairs exist.

The chair on which I sit can be repaired, and it's the same chair. So it might one day be so repaired that all its material parts have changed, and yet it's remained the same chair throughout. But alternatively, all the new parts might be put together tomorrow, making a different chair. And in a sense it would be the same chair (much as if that possible future chair had time-travelled back to tomorrow). You might say that since there's no entity without identity, there's no chair. (And yet here I sit upon it!)

Or you could say that there is a chair, but that there are various criteria of identity. But let's say the chair doesn't exist. The problem with Jones not existing is that there's clearly a difference between Jones not existing and the chair not existing that's nicely expressed by saying that while Jones is fictional the chair is real. And yet we want to say that the chair doesn't really exist!

If Jones is fictional then Jones doesn't exist. Jones exists as a fictional character.

Incidentally, fictional characters can be given pretty good identity criteria. They can be the same character if the author would have thought so. And we can imagine the author writing more and more about the character forever, even if she doesn't. And we can have different versions of the same character (similarly, there is the man I would have been had I done X and the man I would have been had I done Y).