The experience machine objection is often levied against utilitarian theories that depend on utility being a function of observations or brain states. The version of the argument I'm considering here is a more cruxified version that strips out a bunch of confounding factors and goes something like this: imagine you had a machine you could step into that would perfectly simulate your experience in the real world. The objection goes that since most people would feel at least slightly more willing to stay in reality than go in the machine, there's at least some value to being in the "real" world, therefore we can't accept any branch of utilitarianism that assumes utility is soley a function of observations or brain states.
I think if you accept the premise that the machine somehow magically truly simulates perfectly and indistinguishably from actual reality, in such a way that there is absolutely no way of knowing the difference between the simulation and the outside universe, then the simulated universe is essentially isomorphic to reality, and we should be fully indifferent. I'm not sure it even makes sense to say either universe is more "real", since they're literally identical in every way that matters (for the differences we can't observe even in theory, I appeal to Newton's flaming laser sword). Our intuitions here should be closer to stepping into an identical parallel universe, rather than entering a simulation.
However, I think it's not actually possible to have such a perfect experience machine, which would explain our intuition for not wanting to step inside. First, if this machine simulates reality using our knowledge of physics at the time, it's entirely possible that there are huge parts of physics you would never be able to find out about inside the machine, since you can never be 100% sure whether you really know the Theory of Everything. Second, this machine would have to be smaller than the universe in some sense, since it's part of the universe. As a result, the simulation would probably have to cut corners or reduce the size of the simulated universe substantially to compensate.
These things both impact the possible observations you can have inside the machine, which allows you to distinguish between simulation and reality, which means it's totally valid to penalize the utility of living inside a simulation by some amount depending on how strongly you feel about the limitations (and how good the machine is). Just because there's a penalty doesn't mean that other factors can't overcome that, though. Lots of versions of the objection try to sweeten the deal for the world inside the machine further ("you can experience anything you want"/"you get maximum serotonin"/etc); this doesn't really change the core of the argument of whether our utility function should depend on anything other than observations. If the perks are really good and you care less about the limitations than the perks, then it makes perfect sense to go inside the machine; if you care more about the limitations than the perks, it makes perfect sense not to go inside the machine.
The crux of the experience machine thought experiment is that even when all else is held constant, we should assign epsilon more utility to whatever is "real", therefore utility does not depend soley on your observations/brain states. I argue that this epsilon penalty makes sense given practical limitations to any real experience machines, which is probably what informs our intuitions, and that if you somehow handwaved those limitations way then we really truly should be indifferent.
I see what you're trying to get at here, but as stated I think this begs the question. You're assuming here that the only ways universes could differ that would matter would be ways that have some impact on what we experience. People who accept the experience machine (let's call them "non-experientialists) don't agree. They (usually) think that whether we're deceived, or whether our beliefs are actually true, can have some effect on how good our life is.
For example, consider two people whose lives are experientially identical, call them Ron and Edward. Ron lives in the real world, and has a wife and two children who love him, and whom he loves, and who are a big part of the reason he feels his life is going well. Edward lives in the experience machine. He has exactly the same experiences as Ron, and therefore also thinks he has a wife and children who love him. However, he doesn't actually have a wife and children, just some experiences that make him think he has a wife and children (so of course "his wife and children" feel nothing for him, love or otherwise. Perhaps these experiences are created by simulations, but suppose the simulations are p-zombies who don't feel anything). Non-experientialists would say that Ron's life is better than Edward's, because Edward is wrong about whether his wife and children love him (naturally, Edward would be devastated if he realized the situation he was in; it's important to him that his wife and children love him, so if he found out they didn't, he would be distraught). He won't ever find this out, of course (since his life is experientially identical to Ron's, and Ron will never find this out, since Ron doesn't live in the experience machine). But the fact that, if he did, he would be distraught, and the fact that it's true, seem to make a difference to how well his life goes, even though he will never actually find out. (Or at least, this is the kind of thing non-experientialists would say.)
(Note the difference between the way the experience machine is being used here and the way it's normally used. Normally, the question is "would you plug in?" But here, the question is "are these two experientially-identical lives, one in the experience machine and one in the real world, equally as good as each other? Or is one better, if only ever-so-slightly?" See this paper for more discussion: Lin, "How to Use the Experience Machine")
For a somewhat more realistic (though still pretty out-there) example, imagine Andy and Bob. Once again, Andy has a wife and children who love him. Bob also has a wife and children, and while they pretend to love him while he's around, deep down his wife thinks he's boring and his children think he's tyrannical; they only put on a show so as not to hurt his feelings. Suppose Bob's wife and children are good enough at pretending that they can fool him for his whole life (and don't ever let on to anyone else who might let it slip). It seems like Bob's life is actually pretty shitty, though he doesn't know it.
Ultimately I'm not sure how I feel about these thought experiments. I can get the intuition that Edward and Bob's lives are pretty bad, but if I imagine myself in their shoes, the intuition becomes much weaker (since, of course, if I were in their shoes, I wouldn't know that "my" wife and children don't love "me"). I'm not sure which of these intuitions, if either, is more trustworthy. But this is the kind of thing you have to contend with if you want to understand why people find the experience machine compelling.
I guess in that case I think what I'm doing is identifying the experience machine objection as being implied by Newton's flaming lazer sword, which I have far stronger convictions on. For those who reject NFLS, then I guess my argument doesn't really apply. However, at least I personally was in the category of people who firmly accept NFLS and also had reservations about the experience machine, so I don't think this implication is trivial.
As for the Andy and Bob situation, I think that objections like that can be similarly dissolved, given an acceptance of... (read more)