I only just saw this comment. I think that there’s a lot of value in imagining the possibility of both a real you and a hypothetical you, but I expect Schwarz would object to this as the problem statement says, “you”. By default, this is assumed to refer to a version of you that is real within the scope of the problem, not a version that is hypothetical within this scope. Indeed, you seem to recognise that your reasoning isn’t completely solid when you ask what these hypothetical selves even mean.
Fortunately, this is where some of my arguments from Deconfusing Logical Counterfactuals can come in. If we are being blackmailed and we are only blackmailed if we pay out, then it is logically impossible for us to not pay out, so we don’t have a decision theory problem. Such a problem requires multiple possible actions and the only way to obtain this is by erasing some of the information. So if we erase the information about whether or not you are being blackmailed, we end up with two possibilities: a) you paying the the situation and getting blackmailed or b) you not being the kind of person who would pay and you not getting blackmailed. And in that case we’d pick option a).
We can then answer your the question about how your decision affects the past—it doesn’t. The past is fixed and cannot be changed. So why does it look like your decision changes the past? Actually, your decision is fixed as well. You can’t actually change what it will be. However, both you decision and the past may be different in counterfactuals, after all, they aren’t factual. If we have a perfect predictor and we posit a different decision, then we must necessarily posit a different prediction in the past to maintain consistency. Even though we might talking colloquially about changing a decision, what’s actually happening is that we are positing a different counterfactual.
I only just saw this comment. I think that there’s a lot of value in imagining the possibility of both a real you and a hypothetical you, but I expect Schwarz would object to this as the problem statement says, “you”. By default, this is assumed to refer to a version of you that is real within the scope of the problem, not a version that is hypothetical within this scope. Indeed, you seem to recognise that your reasoning isn’t completely solid when you ask what these hypothetical selves even mean.
Fortunately, this is where some of my arguments from Deconfusing Logical Counterfactuals can come in. If we are being blackmailed and we are only blackmailed if we pay out, then it is logically impossible for us to not pay out, so we don’t have a decision theory problem. Such a problem requires multiple possible actions and the only way to obtain this is by erasing some of the information. So if we erase the information about whether or not you are being blackmailed, we end up with two possibilities: a) you paying the the situation and getting blackmailed or b) you not being the kind of person who would pay and you not getting blackmailed. And in that case we’d pick option a).
We can then answer your the question about how your decision affects the past—it doesn’t. The past is fixed and cannot be changed. So why does it look like your decision changes the past? Actually, your decision is fixed as well. You can’t actually change what it will be. However, both you decision and the past may be different in counterfactuals, after all, they aren’t factual. If we have a perfect predictor and we posit a different decision, then we must necessarily posit a different prediction in the past to maintain consistency. Even though we might talking colloquially about changing a decision, what’s actually happening is that we are positing a different counterfactual.