Topics Freedom

Question I have a question about determinism, prediction and conscious choice. Suppose we live in a deterministic universe such that some epistemically-juiced Demon could predict future events with absolute certainty long in advance. When he sits observing, he's always right about what people are going to do. But, suppose, the Demon gets a little bored decides to try to impress some humans with his gift of prophecy. He tells me that he can predict any of my actions: for example, what I'm about to eat for lunch. He gives me an envelope and tells me to open it after I've made my lunch. I do and he's right about the sandwich I was just about to bite into. But at that point can't I just as well change my mind and eat something else? And isn't that true no matter what prediction is made, provided I'm aware of it sufficiently in advance of its "coming true"? Of course, the Demon could have made auxiliary predictions about how his telling me would affect my choice. And those could be true. But if I'm privy to them sufficiently in advance can't I always negate them if I'm so inclined? And so on all the way down... It seems like while there could be a predictable fact of the matter about my choices in advance of their "happening" any prediction of it of which I become aware seems to leave me, from a first-person perspective, with a choice as to whether I will, in fact, "fulfill" the prediction. What do you make of this problem?

Accepted:
July 19, 2012

Comments

Could you or the Demon even understand what he tells you? The Demon tells you (a) that he has predicted what you'll eat for lunch. Of course, now that he's told you that, what he's really told you is (b) that he has predicted what you'll eat for lunch given that he's told you (a). Notice that (b) isn't the same item of information as (a). But wait. If he's told you (b), then really what he's told you is (c) that he has predicted what you'll eat for lunch given that he's told you (b). Notice that (c) isn't the same item of information as (b) or (a). And so the regress continues, forever. Therefore, I wonder if anyone can understand the story you've sketched well enough to see what the story implies or what's consistent with it.

In this article, my co-author and I raised a similar worry in regard to Newcomb's problem, a famous problem in rational decision theory that also involves a predictor. But I'm not sure anyone else was convinced by our argument! In any case, you can find material that's relevant to your question by looking into Newcomb's problem; you might start with this SEP article or this Wikipedia entry. Enjoy!