Homesuck: Vriska Rising

[Aldurin]

Isn't that even more evidence as to the fact that I DON'T GET THIS WEIRD TIME SHIT?

[POS Industries]

Originally Posted by Geminex

Hmm... different points, really.
I'm saying that there's a pretty major limit to timelines. You're saying that when timelines come to exist, they don't interfere with the past. Different points. They're not mutually exclusive, though.

True. The only alternate timelines that we ever have to give a shit about are the ones with Daves popping up.

Also, it just occurred to me that the timeline split may not have been a result of Dave's deciding which side meant what before she flipped as much as it was whether or not Dave stuck to his decision after the fact, since he would have had to make the choice before she flipped, which means the timeline would have split BEFORE she flipped, which means one of the Daves never would have known what the result was.

So basically in one timeline, Dave lied.

[Art of Hilt]

That's possible, unless the timeline doesn't split until Terezi tells him the result and he acts on it. Before then the decision would have only existed in his head and he'd have no incentive to act on it. Only after he is told the results of the time flip does the decision have any practical bearing on the timeline.

This is why Terezi told him not to tell her his decision beforehand.

Offshoot Dave lost contact with her the moment he was told the result. Luckily, since he went back in time immediately to sleep on the Quest Bed in the alpha timeline, he didn't notice that the timeline he just abandoned was a doomed one.

It's all pretty clever of Terezi, really.

It's also pretty cruel. Not only is there now a doomed Dave on the bed placed there specifically by her machinations to die, but also an entire doomed timeline from which Dave never returns, and the kids in it are inevitably doomed as well.

[POS Industries]

Still wouldn't work, because as soon as he made the decision, even if he didn't act on it, it would have technically been a separate timeline because he did something different, if only in his head, and he would have lost contact with Terezi.

[Art of Hilt]

It does because the decision and him acting on it is defined by him being told the result, though. He would not act on it without being told the toss. In fact, until then, it is irrelevant and only exists in his head as the stuff of fantasy.
Because what if it landed on the Good Heads instead? From Dave's perspective, that was still a possibility. Dave did not know that it will always be Bad Heads across all possible timelines. The idea that this decision would split the timeline did not ever come to mind. The illusion of the Good Head kept him from making an actual decision that splits the timeline.
That's why the decision doesn't create a split until after he's told the result. It's also why it's was so crucial that he was given instructions on what to do before he was told the result. Including not telling Terezi his decision out loud.
So basically the split happens after he's told the result, and the inclusion of the coin and the illusion of chance was constructed by Terezi specifically so that this would happen.

[POS Industries]

But when he made the decision, that already created two different Daves. One Dave decided that the coin flip meant one thing, the other Dave decided the opposite. That's already two different timelines. Two different Daves.

[Art of Hilt]

But it was still "up in the air" because he didn't know the results of the coin flip, because to him it could have still been Good Heads and he would have done the opposite.
At most it was a framework of how a future decision was to be made, immaterial on its own without knowledge of the coin flip's results.

[POS Industries]

It doesn't matter if what manual action he would have taken was still "up in the air" because he already made the decision before the flip.

Even if he'd done the exact same thing afterward in both timelines, it would have still been two separate timelines that moved on exactly the same way, except in one he had one thought and in the other he had a different thought. Thinking isn't magically exempt from altering the course of history on a temporal level.

[Marc v4.0]

I'm not seeing where people aren't getting it. She explained it rather clearly and, frankly, it's the most un-bullshit time bullshit I have ever seen.

[POS Industries]

Actually, now that I think about it, the only way that this does work the way Terezi explained it is if thought really is magically exempt from altering the flow of time, which is technically complete bullshit on a realistic level but pretty much nothing about the entire premise of this comic is really grounded in any sort of reality.

So I ain't gonna pitch a fit about it.