OrangePhilosophy

Limited options, it seems. If I travel back in time to when I was 18 (which would be nice), either I go to the time-and-world exactly as it was then (on the same line), or I create an alternate line. I don't really like these options, because it looks like we'd be stuck with an alternate time. But imagine that two people had a time machine. They both create (?) alternate times. Presumably we are in both times and the oroginal one too. So, if we can imagine two time machines, why not imagine an indefinite number of times--possible times that may be realized when someone travels to it. There's other stuff that needs to be said about this, but it's getting a little strange at this point.
I'm not quite sure what baronofdeseret is saying about movement, but if this is the same as change, then it seems close. I guess, without knowing much (anything) about philosophy of time travel (?), that time travel doesn't shore up with basic notions of causation. Maybe it's enough to ditch theories of time travel just for this reason. But that doesn't mean that we need to follow MacTaggart's medieval conclusion to the letter. There is something about change that is important. Whitehead picked up on this. I suggest that we start there, if only to extract what is said about the passage of time.

The first option isn't necessarily an alternate timeline, because if you go back to when you were 18 you will be fulfilling the past. Somehting already happened, and you may or may not know about it, but then you go back and discover that you're the one who made it happen.

My thought about time travel and causation is simply that it would be one of the few kinds of backward causation. In a consistent timeline view, it seems relatively unproblematic to have backward causation of certain sorts. Dummett has a famous paper arguing for this with the example of praying for someone who has survived a plane crash (but you don't know that), with God having known in advance that you would pray for the person and has already answered it by saving the person's life. That seems like a perfectly reasonable kind of backward causation, and time travel shouldn't be any different.

Hi Jeremy - You get can unexplained causal loops with all reverse causation (and you will, unless you basically stipulate away anything loopy), and I think we might need different explanations for different explanatory "lacks". The ones that seem weirdest are loopy objects, say a diamond which you find in a safety deposit box, bring it back in time to sell (since it's hard to exchange money cross-temporally) and the buyer locks it up in a safety deposit box. Most diamonds are generated from ancient carbon under incredible pressure, so why isn't this one? Weird, even if it is consistent.

Then there's the classic "you receinve plans from the future on how to build a time machine, build it, and send plans for it into the past." This doesn't need to involve material loops. Maybe the plans are sent digitally by flipping spin states of present electrons "non-locally" (and from the future). Already it's hard to dispute that immediate-action-at-great-distance really happens, so maybe we'll figure out how to do this at a temporal distance.

This, I think, should lead us to distinguish explaining objects (diamond) and explaining events (superposition collapses, or whatever). I bet there's a literature on this, but I don't know it. One difference that stikes me: the time machine in the second case is made from stuff of "ordinary origin" whose history can be traced to the big bang. My gut feeling is that I'm not prepared to bang my fist and insist this is impossible, metaphysically or physically.

Divine foreknowledge cases of backward causation don't necessarily allow unexplained causal loops, particularly if you allow theological determinism fromt he outset. The foreknowledge then is based on knowledge of how the deterministic events will take place, including the choice to pray foreseen by God that God earlier acts on.

For some reason the time machine thing doesn't seem as worrisome to me as the watch one. For some reason unexplained existence seems worse than a simple causal loop.

I think you do get causal loops when the Divine foeknower acts on foreknowledge in a way that causally influences what is known.

So God forsees Moses' amusing reaction to the burning bush. God thinks "this will be cool" and ignites the bush in order to bring about the amusing result.

That's not so weird.

THIS IS FICTION...
I was considering something. Suppose someone I know has a Time Machine. Something very bad happens in our future, let's say a bad war sometime after the year 2017 ce. My friend with the Time Machine comes back to the present monent and tries to prevent the worst case scenario War from happening. Only after my friend time-travels to the present moment to prevent the war do they find that they themselves brought into being the chain of events that caused the very war they were trying to prevent. And they travel back and forth along the time line and watch the same exact sequence of events happen over and over exactly the same. Only "after the fact" do they realize in extreme frustration that not only did they casue what they were trying to prevent, but it keeps happening the EXACT same way. I wonder if we would call that Determinism and leave out the backward causation bit.

I'm not sure I want to call it determinism, because that thesis is about the laws of nature determining how one complete set of conditions will lead to another. Once you have time travel from the future to the past, that throws a wrench in how you think about determinism. There are some clear similarities, of course, but that doesn't make it the same thing.

Even if you did want to call it determinism, that wouldn't make it not backward causation. The reason it happens the way it does is because you came from the future to try to prevent it. Since it was always true that it would happen for that reason, then it was always true that was caused it was your trip from the future. Just the fact that you're now in the past because of something you did in the future is backward causation, so I just don't see how you can get out of calling it that.

This old post is still kickin? Well, I really have to ask, Jeremy, if you have any statement of your views on time that one might easily get to. I tend to think that what you said is confusing:
"Since it was always true that it would happen for that reason, then it was always true that was caused it was your trip from the future."
Is there something beyond eternalism that you suppose? I thought at first you meant something like...from the God's eye view...which is what I take eternalism to be. Maybe thats it. Please, run my shorts up the flag pole.

It should be: "Since it was always true that it would happen for that reason, then it was always true that what caused it was your trip from the future."

Other than that, I'm not sure what you think this involves that's beyond simple eternalism with its unchangeable timeline. That's all I was really getting at.