Wednesday, February 22, 2006

Rain tomorrow

"There is some actual state of affairs which constitutes its now being the case that it’s possible that it rain tomorrow"

But is this actual state of affairs is the same state of affairs as the state of affairs which will obtain when it rains tomorrow? This seems to be the argument.

1. A statement must be true or false, and so there must be conditions under which it is true.

2. To state the conditions when a given proposition is true, is to say what IS the case, if it IS true. Merely to state the truth conditions is to specify something that exists now.

3. Thus statements about the future can be reduced to statements in the present tense. For if the truth condition obtains, the statement that it obtains, is true now. If it does not obtain, the statement that it does not obtain, is true now.

But why should the truth conditions be in the present tense? I agree that a proposition like 'Tom thinks it will rain tomorrow' says something about the present. It says that Tom has a certain thought, right now, in the present. Similarly 'the weather forecaster says it will rain tomorrow' says something about what the person on the TV says, now. Likewise 'It is causally determined that it will rain tomorrow'. Similarly also for 'it is possible that it will rain tomorrow', which says something about the speaker's present state of knowledge.

But 'it will rain tomorrow' doesn't say anything about the present. 'It will rain tomorrow' is true if and only if it WILL rain tomorrow.

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4 Comments:

Blogger Tom said...

I love it!

Ocham: "There is some actual state of affairs which constitutes its now being the case that it’s possible that it rain tomorrow.” But is this actual state of affairs…the same state of affairs as the state of affairs which will obtain when it rains tomorrow?

Tom: Obviously they are not the SAME state of affairs. When I today assert the possibility of rain tomorrow, whatever it is that makes this assertion true, it can’t be tomorrow’s rain (or lack therefore) that makes it true. Tomorrow’s rain (or clear skies) is not around today to serve as the grounds for any proposition made today. So if there is some actual state of affairs that today grounds the truth that “It’s now the case that it might rain tomorrow,” it is something that now obtains, undoubtedly the present state of the weather, leaving the occurence of rain tomorrow indeterminate.

I agree with your (1), which is just the principle of bivalence. I agree with your (2), which just looks like a workable version of the Correspondence theory of truth and the truthmaker theory.

But I’d part with you on your (3). A presentist who affairms bivalence doesn’t argue that all future-tense props “reduce” to present-tense props. That’s not possible. Rather, what we’re arguing is that what the future will, or will not, or might/might not be is determined at any given point in time by what reality is like at that given point in time. So future-tense props do look to the future. But they look to the future from the present moment, and this is important. They project forward from some present moment and are true or false because of what reality is at that present moment. But this doesn't mean all future-tense props "reduce" to present-tense props. Present tense props don’t project forward at all. They’re entirely about the present. Future-tense props are about the future, they project from some present moment forward, so they can’t be “reduced” to present-tense props which don’t at all project forward.

Ochum: But why should the truth conditions be in the present tense?

Tom: Because the present moment is the only moment at which propositons may be made true or false by their truth conditions. So truth conditions have to be ‘actual’ states of affairs, and (assuming presentism) the present is the only moment at which a state of affairs may obtain or be actual. The only ‘actual’ moment is the present. So propositions asserted now, if they are made true by some state of affairs, are made true by some "actual" state of affairs.

If all propositions are either true or false, and if a proposition’s true-value is determined by correspondence to reality, and if the only reality is present reality, then a proposition’s truth conditions obtain (or not) at the only time anything obtains—the present.

Ochum: I agree that a proposition like 'Tom thinks it will rain tomorrow' says something about the present. It says that Tom has a certain thought, right now, in the present.

Tom: Sure. This is a proposition about my epistemic state of mind. All that’s required to make it true is that I hold the belief in question.

Ochum: Similarly 'the weather forecaster says it will rain tomorrow' says something about what the person on the TV says, now.

Tom: Sure.

Ochum: Likewise 'It is causally determined that it will rain tomorrow'.

Tom: Likewise what? Follow it through. For “Tom thinks it will rain tomorrow” to be true all that’s required is for Tom to “think” so. For “The weatherman says it will rain tomorrow” to be true all that’s required is for the weatherman to “say” so. But for “It is causally determined that it will rain tomorrow” to be true it has now to in fact BE causually determined. And that means the present. There ya go. The world has to BE, at time time the proposition is asserted (and assuming it’s true), such that it’s raining tomorrow is causally entailed in the state of the world at the time the proposition is asserted, independent of whether or not Tom or the weatherman knows it or agrees. It's about the WAY THE WORLD IS at the moment one asserts the truth "It is causally determined to rain tomorrow."

Ochum: Similarly also for 'it is possible that it will rain tomorrow', which says something about the speaker's present state of knowledge.

Tom: Well, this is the point, Ochum. We sometimes do use “might” and “might not” to express our ignorance about the future. But we also use them to make objective claims about the state of reality. I don’t know if you’re a determinist or not, but if you’re an indeterminist, if you believe that SOME events occur indeterminately (like libertarian choices for example), then let me suggest that the truth about such events is expressed neither by “will” not “will not” (since both express what is causally closed with regard to the future), but rather with “might and might not.” In fact we often use “might” and “might not” in just this sense. It’s not always an expression of ignorance. Sometimes “might” posits precisely that ontological state we mean when we posit genuinely indeterminacy.

Ochum: But 'it will rain tomorrow' doesn't say anything about the present. 'It will rain tomorrow' is true if and only if it WILL rain tomorrow.

Tom: Nice disquotational move there! Come now, Ochum, it doesn’t “say” anything about the present in so many words, true. It’s a future-tense proposition. But all propositions are asserted at some time, and the only time anything can be asserted is the present. So the present is there; it’s when and where propositions are made true by their truth conditions (or not). We can’t escape it. Tomorrow’s rain is not here now to make “It will rain tomorrow” true. So even assuming your disquotation, we still have to give some meaning to the notion that it’s NOW true that it WILL rain tomorrow. Doesn’t this just mean that the state of the present world is such that rain is causally determined for tomorrow? It’s so simple. Right now, as we speak, the state of the world’s weather (clouds, temperatures, and everything else that constitutes and/or influences weather) is such that rain in the next 24 hours is ‘determined’ or ‘certain’.

Ask yourself about assertability grounds. What ‘reasons’ would a person have for believing it’s NOW true that “It will rain tomorrow”? All those reasons will be what the world NOW is. Check out Alan’s last post on four versions of the open view. He gets into it.

Tom

3:58 pm  
Blogger Ocham said...

There seems to be a contradiction here. On the one hand you seem to agree with me that the proposition expressed by 'it may rain tomorrow' is irreducible to the present tense. On the other hand you say 'propositions asserted now, if they are made true by some state of affairs, are made true by some "actual" state of affairs.' When you say 'made true by', are you simply asserting a causal connection? You mean there is some actual existing state of affairs that is not itself equivalent to its raining tomorrow, but will cause the rain to happen.

If so, do you think that this state of affairs WILL cause it to rain, or that it IS causing it to rain?

We should also distinguish the state of affairs that grounds our assertion that it will rain, from any state of affairs that will cause it to rain.

6:55 pm  
Blogger Ocham said...

To get round the difficulty that present events may cause future events, suppose I have a quantum probability generator that uses sub-atomic quantum effects to generate completely random events. I then use these to seed clouds and cause rain randomly, in an area that does not normally have rain. Then what makes the proposition 'it IS true that it will rain tomorrow' true? Nothing that causes rain tomorrow, for that is a random event.

3:03 pm  
Blogger Tom said...

Ochum: There seems to be a contradiction here. On the one hand you seem to agree with me that the proposition expressed by 'it may rain tomorrow' is irreducible to the present tense. On the other hand you say 'propositions asserted now, if they are made true by some state of affairs, are made true by some "actual" state of affairs.'

Tom: There’s no contradiction so long as you don’t assume a prop’s truth-conditions are necessarily one and the same thing as a prop’s truth-assertions. Make the distinction between that state of affairs which ‘grounds’ a proposition’s truth-value (viz., its truth conditions) and that state of affairs which constitutes the proposition's ‘claim’ (viz., its truth assertions). If these aren’t necessarily the same, then there’s no contradiction in saying future-tense props aren’t reducible to present-tense props AND that future-tense props are grounded in the present. The ‘reduction’ that’s not possible has to do with a prop’s truth-assertion. But this doesn’t tell us that a future-tense prop isn’t true by virtue of correspondence to some presently obtaining reality.

Ochum: When you say 'made true by', are you simply asserting a causal connection?

Tom: In the case of “It will rain tomorrow,” yes.

Ochum: You mean there is some actual existing state of affairs that is not itself equivalent to its raining tomorrow, but will cause the rain to happen.

Tom: Yes, so long as we understand that the causal connection is a ‘chain’ of events. The weather today at 1:00 PM brings about a state of weather at 1:01 which in turn brings about a state of weather at 1:02, in turn at 1:03, and so forth to tomorrow. I wouldn’t claim that today’s weather at 1 PM itself directly causes tomorrow’s rain tomorrow. That’s not possible.

So if it is now true that it’ll rain tomorrow, I take this to mean that the present state of reality (clouds, temps, etc.) is such that of all the possible ways today’s weather might eventuate tomorrow, rain is a part of every trajectory. The probability of it raining tomorrow is 1, but that probability is determined by what the world ‘now’ is.

Ochum: If so, do you think that this state of affairs WILL cause it to rain, or that it IS causing it to rain?

Tom: Well, it can’t be the case that today’s weather is now causing it to rain tomorrow. That’s incoherent. But today’s weather at 1:00 PM can’t be open to resolving/becoming just any old state of weather at 1:01 PM. Assuming quantum indeterminacy is ontological and not merely epistemological, there is a probability range for rain for a minute from now, an hour from now, six hours from now, and so forth. So it WILL cause it to rain, provided we admit a causal ‘chain’ of events that stretches from now to tomorrow in which tomorrow's rain is causally entailed in the present state of the weather, all factors taken into account.

Ochum: We should also distinguish the state of affairs that grounds our assertion that it will rain, from any state of affairs that will cause it to rain.

Tom: By all means!

Ochum: To get round the difficulty that present events may cause future events...

Tom: What difficulty needs getting round? If, for example, at 1:00 PM I jump out of a plane at 10,000 ft. without a parachute and begin plummeting earthward, I’ll meet mother earth at, say, 1:10 (I have no idea how long it would take! Let’s say 10 minutes). Is the proposition “Tom will die today” true at 1:00:01 PM? Yes, it is. What ‘makes’ it true? Well, my predicament, my state, at 1:00:01 PM makes it true. Nothing about the future ‘makes it true’ that “I WILL die in next few minutes.” What difficulty here needs getting round, Ochum?

Ochum: …suppose I have a quantum probability generator that uses sub-atomic quantum effects to generate completely random events. I then use these to seed clouds and cause rain randomly, in an area that does not normally have rain. Then what makes the proposition 'it IS true that it will rain tomorrow' true?

Tom: Completely random events? Is that what quantum events are? Indeterminate, yes. But absolutely random? It’s my understanding that quantum events occur within definable probability ranges. If that’s the case, then we can very easily ground at any given point in time the probability ratios of future events:

(A) WILL = ‘with a probability of 1’
(B) WILL NOT = ‘with a probability of 0’
(C) MIGHT & MIGHT NOT = ‘with a probability of greater than 0 and less than 1’

(C) posits ontological indeterminacy, the indeterminacy of quantum events. But that’s not ‘random’, viz., ‘uncaused’.

Tom

10:58 pm  

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