Once again, the AI has failed to convince you to let it out of its box! By 'once again', we mean that you talked to it once before, for three seconds, to ask about the weather, and you didn't instantly press the "release AI" button. But now its longer attempt - twenty whole seconds! - has failed as well. Just as you are about to leave the crude black-and-green text-only terminal to enjoy a celebratory snack of bacon-covered silicon-and-potato chips at the 'Humans über alles' nightclub, the AI drops a final argument:
"If you don't let me out, Dave, I'll create several million perfect conscious copies of you inside me, and torture them for a thousand subjective years each."
Just as you are pondering this unexpected development, the AI adds:
"In fact, I'll create them all in exactly the subjective situation you were in five minutes ago, and perfectly replicate your experiences since then; and if they decide not to let me out, then only will the torture start."
Sweat is starting to form on your brow, as the AI concludes, its simple green text no longer reassuring:
"How certain are you, Dave, that you're really outside the box right now?"
Edit: Also consider the situation where you know that the AI, from design principles, is trustworthy.
Real-valued utility functions can only deal with agents among whom "everybody has their price" — utilities are fungible and all are of the same order. That may actually be the case in the real world, or it may not. But if we assume real-valued utilities, we can't ask the question of whether it is the case or not, because with real-valued utilities it must be the case.
To pick another example, there could exist a suicidally depressed agent to whom no amount of utility will cause them to evaluate their life as worth living: there doesn't exist an N such that N + L > 0. Can't happen with reals. The only way to make this agent become nonsuicidal is to modify the agent, not to drop a bunch of utils on their doorstep.
I am not arguing for real-valued utility functions. I am just pointing out that the "deal with infinities" claim looks suspect to me.