There is a further temporal fact about a given event: whether it is in the past, in the present or in the future.
In the past, present or future of what?
Of me, who is saying it? But that is merely a temporal fact of the first kind: the given event is in the past/future of the event of my saying whether it is in my past/future.
The point of A-theory is that past, present and future are non-relational. There is an objective fact of the matter about which slice of the space-time manifold is the present, although this fact keeps changing, of course. So yeah, one way to think of the difference between A-theory and B-theory is that the B-theorist thinks of past, present and future as relational terms. Just saying “past” isn’t enough, you need to specify what it is in the past of. But the A-theorist thinks it makes sense to talk of past, present and future simpliciter.
An event (a point in spacetime) is really objective wrt time: that is, it is outside of time. The ordering of two events is also objective.
The matter of where we are in time—and therefore, whether an event is in our past or in our future—is constantly changing as time flows. It is not a time-objective fact about an event that it is in our future, for tomorrow it will be a fact about the same event that it is in our past. So these facts about an event are subjective: they depend on when in time you are when you are making the judgement.
Disagreeing with this seems like saying the word “objective” should mean two different things in the two above paragraphs. Which is apparently what almost all big philosophical arguments reduce to. Sigh.
So these facts about an event are subjective: they depend on when in time you are when you are making the judgement.
You’re describing a B-theoretical perspective. An A-theorist will disagree with this characterization. Many A-theorists believe that the only objects that exist are present objects. So time isn’t like space, where “here” is “here” rather than “there” simply because you happen to be “here” and not “there”. You could have been “there”, in which case “there” would have been “here” for you. Time, A-theorists claim, is different, because you couldn’t be located anywhere (anywhen) else except in the present. It’s not that the present is the present for you because you happen to be there; it’s that the only time at which objects exist (and, by extension, you could exist) is the present. So it’s not like there are other people who exist at other times, for whom the present is different.
Don’t ask me to defend this view, though, because I think it’s nuts. A-theory vs. B-theory is one of those philosophical debates which should be declared closed. B-theory has clearly won.
I don’t think anyone’s made A-theory consistent with special relativity. But you can bodge general relativity/cosmological models a bit to get something that looks a bit like A-theory by insisting on a preferred foliation (e.g. look at spacelike surfaces with constant proper time since the Big Bang, and count everything on one such surface as the “real now”)
Bourne, from what I recall, makes A-theory consistent with special relativity by positing that there is an (undetectable) privileged reference frame. Is this correct? If it is, I wouldn’t really call that “consistent with special relativity”, more like “flying in the face of the central lesson of special relativity”.
Yeah, that’s basically right but I’m not sure that you’re being entirely fair to Bourne.
First, I think under standard definitions of consistent, he does show that an A-theory is consistent with SR (ie. they can both be true at once).
Second, I’m not sure it’s fair to say that he is “flying in the face of the central lesson of SR”—he may be flying in the face of the standard way of interpreting this lesson but his claim is precisely that this way of intrepreting the lesson isn’t the only way. The lesson can also be interpretted as “no privileged reference frame can be detected.”
I agree with the basic anti-Bourne sentiment but wonder whether the wording of your response undermines his claims more than they deserve—I don’t think they are inconsistent nor that they fly in the face of the central lesson. I guess I more just think that postulating undetectable physical features of the world in order to make a metaphysical thesis - that is based on intuition (the “present” intuition) that can be explained away—come out to be true is undesirable.
Though it should be noted that Bourne’s conclusion is mostly that presentism is the only sensible A-theory but that it’s not possible to decide between presentism and a B-theory (that is, he doesn’t argue that presentism must be true).
So this is just like the “bodge” I described for general relativity/cosmology, but with even less justification? The preferred foliation has no physical motivation at all, and is plucked entirely out of the aether (so to speak).
I’m not sure I’d count that as consistent with special relativity. Though in principle it would give the same predictions as special relativity.
In the past, present or future of what?
Of me, who is saying it? But that is merely a temporal fact of the first kind: the given event is in the past/future of the event of my saying whether it is in my past/future.
The point of A-theory is that past, present and future are non-relational. There is an objective fact of the matter about which slice of the space-time manifold is the present, although this fact keeps changing, of course. So yeah, one way to think of the difference between A-theory and B-theory is that the B-theorist thinks of past, present and future as relational terms. Just saying “past” isn’t enough, you need to specify what it is in the past of. But the A-theorist thinks it makes sense to talk of past, present and future simpliciter.
An event (a point in spacetime) is really objective wrt time: that is, it is outside of time. The ordering of two events is also objective.
The matter of where we are in time—and therefore, whether an event is in our past or in our future—is constantly changing as time flows. It is not a time-objective fact about an event that it is in our future, for tomorrow it will be a fact about the same event that it is in our past. So these facts about an event are subjective: they depend on when in time you are when you are making the judgement.
Disagreeing with this seems like saying the word “objective” should mean two different things in the two above paragraphs. Which is apparently what almost all big philosophical arguments reduce to. Sigh.
You’re describing a B-theoretical perspective. An A-theorist will disagree with this characterization. Many A-theorists believe that the only objects that exist are present objects. So time isn’t like space, where “here” is “here” rather than “there” simply because you happen to be “here” and not “there”. You could have been “there”, in which case “there” would have been “here” for you. Time, A-theorists claim, is different, because you couldn’t be located anywhere (anywhen) else except in the present. It’s not that the present is the present for you because you happen to be there; it’s that the only time at which objects exist (and, by extension, you could exist) is the present. So it’s not like there are other people who exist at other times, for whom the present is different.
Don’t ask me to defend this view, though, because I think it’s nuts. A-theory vs. B-theory is one of those philosophical debates which should be declared closed. B-theory has clearly won.
I don’t think anyone’s made A-theory consistent with special relativity. But you can bodge general relativity/cosmological models a bit to get something that looks a bit like A-theory by insisting on a preferred foliation (e.g. look at spacelike surfaces with constant proper time since the Big Bang, and count everything on one such surface as the “real now”)
See Craig Borne “A Future for Presentism” for someone who claims to have made an A-theory consistent with special relativity.
Bourne, from what I recall, makes A-theory consistent with special relativity by positing that there is an (undetectable) privileged reference frame. Is this correct? If it is, I wouldn’t really call that “consistent with special relativity”, more like “flying in the face of the central lesson of special relativity”.
Yeah, that’s basically right but I’m not sure that you’re being entirely fair to Bourne.
First, I think under standard definitions of consistent, he does show that an A-theory is consistent with SR (ie. they can both be true at once).
Second, I’m not sure it’s fair to say that he is “flying in the face of the central lesson of SR”—he may be flying in the face of the standard way of interpreting this lesson but his claim is precisely that this way of intrepreting the lesson isn’t the only way. The lesson can also be interpretted as “no privileged reference frame can be detected.”
I agree with the basic anti-Bourne sentiment but wonder whether the wording of your response undermines his claims more than they deserve—I don’t think they are inconsistent nor that they fly in the face of the central lesson. I guess I more just think that postulating undetectable physical features of the world in order to make a metaphysical thesis - that is based on intuition (the “present” intuition) that can be explained away—come out to be true is undesirable.
Though it should be noted that Bourne’s conclusion is mostly that presentism is the only sensible A-theory but that it’s not possible to decide between presentism and a B-theory (that is, he doesn’t argue that presentism must be true).
So this is just like the “bodge” I described for general relativity/cosmology, but with even less justification? The preferred foliation has no physical motivation at all, and is plucked entirely out of the aether (so to speak).
I’m not sure I’d count that as consistent with special relativity. Though in principle it would give the same predictions as special relativity.