Let’s return for a moment to the question at the end of this post. I asked, “What happens if the future is indeterminate? Would not the eternalist position necessarily differ from the presentist one, in that case?”
Why necessarily different? The argument in that post was that eternalism and presentism are different descriptions of the same thing, and that we see the sameness by noting the sameness of relations between the elements of the description. But if the future is open, as Aristotle supposed, it is hard to see how we can maintain this. Aristotle says that the present is open to either having the sea battle tomorrow or not having it. With an eternalist view, the sea battle is “already there” or it is not. So in Aristotle’s view, the present has an open relationship to both possibilities. But the eternalist view seems to be truly open only to the possibility that will actually happen. We no longer have the same set of relationships.
Notice the problem. When I attempted to equate eternalism and presentism, I implicitly assumed that determinism is true. There were only three states of the universe, beginning, middle, and end. If determinism is false, things are different. There might be beginning, middle, and two potential ends. Perhaps there is a sea battle in one of the potential ends, and no sea battle in the other.
This suggests a solution to our conundrum, however. Even the presentist description in that post was inconsistent with an open future. If there is only one possible end, the future is not open, even if we insist that the unique possible end “currently doesn’t exist.” The problem then was not eternalism as such, but the fact that we started out with a determinist description of the universe. This strongly suggests that if my argument about eternalism and presentism was correct, we should be able to formulate eternalist and presentist descriptions of an open future which will be equivalent. But both will need to be different from the fixed “beginning-middle-end” described in that post.
We can simply take Aristotle’s account as the account of presentism with an open future. How can we give an eternalist account of the same thing? The basic requirement will be that the relationship between the present and the future needs to be the same in both accounts. Now in Aristotle’s account, the present has the same relationship to two different possibilities: both of them are equally possible. So to get a corresponding eternalist account, we need the present to be equally related to two futures that correspond to the two possiblities in the presentist account. I do not say “two possible futures,” but “two futures,” precisely because the account is eternalist.
The careful reader will already understand the account from the above, but let us be more explicit. The eternalist account that corresponds to the presentist account with an open future has multiple timelines, all of which “exist”, in the eternalist sense. The reader will no doubt be familiar with the idea of multiple timelines, at least from time travel fiction. In a similar way, the eternalist reworking of Aristotle’s position is that there is a timeline where the sea battle takes place, and another timeline where the sea battle does not take place. In this view, both of them “actually” happen. But even in this view, an observer in the middle location will have to say, “I do not, and cannot, know whether the sea battle will take place or not,” just as in Aristotle’s view. For the observer cannot traverse both timelines at once. From his point of view, he will take only one, but since his relationship to the two possibilities (or actualities) is the same, it is indeterminate which one it will be.
Even if one cannot prove my account of equivalence to be wrong, the reader may worry. Time travel fiction frequently seems incoherent, and this suggests that any view with multiple timelines may also be incoherent. But this potential incoherence supports the equivalence, rather than subtracting from it. For as we noted in the post on Aristotle, there is a definite appearance of incoherence in his position. It is not even clear how his view is logically possible. So it would not be surprising, but quite natural, if views which are intended to be equivalent to his position are also not clearly coherent. Nonetheless, the multiple timelines description does have some logical advantage over Aristotle’s position, in the sense that “the sea battle will take place in timeline A” does not even appear to contradict “the sea battle will not take place in timeline B.”
Entirely Useless 
It should not surprise anyone that there will be one, and only one future. After all, we have one, and only one past, to put it in. The meaningful and relevant question then is this: How will this single, inevitable future be causally determined?
Well, what do we have to work with? We observe that the real world consists of physical objects, from the very small, like photons and electrons, to the very large, like stars and galaxies. These objects fall into three major classes: (1) inanimate objects, that passively obey the laws of physics, (2) living organisms, that are animated by biological drives to survive, thrive, and reproduce, and (3) intelligent species, that are able to imagine possibilities, estimate how different options might play out, and, based upon these calculations, choose what they will do.
Deterministic inevitability is about what will happen in the real world. But this in no way restricts what can and cannot happen. The inevitable and the possible exist in separate semantic contexts.
When speaking of what we can and cannot do, our context is the mental process of imagination. We use our imagination to play out possible futures, to estimate what comes of choosing this option rather than that option.
We can have as many possibilities as we can imagine. If we foresee an insurmountable roadblock for one possibility, then we may discard it as an “impossibility”. If a possibility is not feasible to implement, then we say it is not a “real” possibility. But all possibilities that could be implemented, if chosen, are referred to as real possibilities.
The possibility that we implement becomes the inevitable actuality. Our choice is the inevitable result of our purpose and our reasons. Our purpose and our reasons are the inevitable result of who we are at that moment. Who we are at that moment, is the inevitable result of our interactions with our physical and social environment up to that point, including all the other choices we made along the way. We are active participants in causally determining who we become.
So, we begin with multiple possibilities, and from them we choose what will become the single inevitable actuality.
Now, if things don’t turn out as we imagined they would, then we may reconsider our choice, and consider what we “could have done otherwise”. This mental process of reconsideration is how we learn from our mistakes, and how we adjust our future choices to produce better outcomes.
If we had more than one real possibility, then it is always true that we could have done otherwise. But, it is also true that we wouldn’t have done otherwise, at that unique point in time.
The “hard” determinist’s assertion that we could not have done otherwise, because everything we do is inevitable, would be ass-backwards. We begin with what we could do, and from that we choose the inevitable actuality.
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We have had this discussion before, and I’ve explained why you are mistaken. There is no need to go over it again.
The next couple of posts are going to be on quantum mechanics and you may want to wait for that. In particular, “It should not surprise anyone that there will be one, and only one future. After all, we have one, and only one past, to put it in,” is completely wrong in quantum mechanics. There is more than one possible future in quantum mechanics, *and more than one past* as well.
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I suspect that quantum mechanics will have its own set of rules at its own level, even if we never discover what they are. Rules are derived by observing reliable patterns of behavior in the object we’re studying, and it’s really hard to get a good look at how things are working down there, especially if it takes a Large Hadron Collider to perform experiments! 🙂
But I would say that it is as if the future is “open” in every meaningful and relevant way, even though it will turn out in precisely one way. The fact that it will turn out one way has no meaningful or relevant implications. All human concepts came into being within a deterministic universe, so we can deduce that every concept subsumes as much.
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Did you read the “action at a distance” post? It is mathematically impossible to give a deterministic explanation of the actual results of quantum mechanics experiments without instantaneous action at a distance. Is that what you think happens?
The point is that “maybe there’s some explanation we just don’t know yet” is not going to work. We ALREADY know that that kind of explanation CANNOT work. It is logically and mathematically impossible.
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It is only because we take gravity for granted that gravity isn’t called “spooky action at a distance”. It may be that one day we’ll be so familiar with the quantum mechanism that its effects will be just as “unspooky”, and just as predictable, as gravity.
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Wrong. In general relativity, gravity acts locally, by bending space bit by bit, until it reaches a body. It does not act instantaneously, and it does not act at a distance.
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