Let's say Bob's terminal value is to travel back in time and ride a dinosaur.
It is instrumentally rational for Bob to study physics so he can learn how to build a time machine. As he learns more physics, Bob realizes that his terminal value is not only utterly impossible but meaningless. By definition, someone in Bob's past riding a dinosaur is not a future evolution of the present Bob.
There are a number of ways to create the subjective experience of having gone into the past and ridden a dinosaur. But to Bob, it's not the same because he wanted both the subjective experience and the knowledge that it corresponded to objective fact. Without the latter, he might as well have just watched a movie or played a video game.
So if we took the original, innocent-of-physics Bob and somehow calculated his coherent extrapolated volition, we would end up with a Bob who has given up on time travel. The original Bob would not want to be this Bob.
But, how do we know that _anything_ we value won't similarly dissolve under sufficiently thorough deconstruction? Let's suppose for a minute that all "human values" are dangling units; that everything we want is as possible and makes as much sense as wanting to hear the sound of blue or taste the flavor of a prime number. What is the rational course of action in such a situation?
PS: If your response resembles "keep attempting to XXX anyway", please explain what privileges XXX over any number of other alternatives other than your current preference. Are you using some kind of pre-commitment strategy to a subset of your current goals? Do you now wish you had used the same strategy to precommit to goals you had when you were a toddler?
When you said to suppose that "everything we want is [impossible]", did you mean that literally? Because normally if what you want is impossible, you should start wanting a different thing (or do that super-saiyan effort thing if it's that kind of impossible), but if everything is impossible, you couldn't do that either. If there is no possible action that produces a favorable outcome, I can think of no reason to act at all.
(Of course, if I found myself in that situation, I would assume I made a math error or something and start trying to do things that I want and that I think I messed up when I decided that the thing was impossible.)
If you didn't mean -everything-, then why not just start pursuing the thing which gives the most value which is possible to do?
Perhaps I misunderstood the question?
I didn't mean it literally. I meant, everything on which we base our long-term plans.
For example:
You go to school, save up money, try to get a good job, try to advance in your career... on the belief that you will find the results rewarding. However, this is pretty easily dismantled if you're not a life-extensionist and/or cryonicist (and don't believe in an afterlife). All it takes is for you to have the realization that
1) If your memory of an experience is erased thoroughly enough (and you don't have access to anything external that will have been alte... (read more)