You're still assuming it's not like sleep, and that you wouldn't be floating in a vat of chemicals/equipment that had an impact on your mental state. And you still shouldn't assume that death is preferable to solitary confinement or sensory deprivation.

> You're still assuming it's not like sleep, and that you wouldn't be floating in a vat of chemicals/equipment that had an impact on your mental state.

I'll point out that the current two-process model we have for sleep pushes the brain towards waking up after a while; Process C (circadian) on a periodic basis and process S after the brain's need for sleep is satisfied. That would need to be counteracted. I'll also point out that there's some evidence that even a few months of sedation will cause lasting cognitive damage, e.g. https://www.nejm.org/doi/full/10.1056/NEJMoa1301372, yet sedation for years, if not decades, would be necessary. The brain is not a machine; it does not shut down when asleep or sedated.

> And you still shouldn't assume that death is preferable to solitary confinement or sensory deprivation.

It is, of course, a personal decision and it might even be said to be the ultimate personal decision. However, not understanding the implications of one's choices, as best we know them, is unwise, don't you think?

Being a brain in a vat doesn't imply much though. I mean, you can't assume someone has lobbed your head of and crudely crammed it into a jar of formaldehyde. For all anyone knows, you're in The Matrix instead. So unless we constrain the problem, there's no more reason to assume it is torture than there is to assume it is euphoria.

As such, there are no implication to being a brain in a vat other than the fact that you don't experience the outside world. It says nothing about what you do experience. And it certainly does not imply permanent damage in the same way that death does.

If one is allowed to assume sci-fi, ... no, not even sci-fi, outright sci-fantasy levels of technology like the Matrix, the question becomes essentially meaningless. One might as well just say a new body will be instantaneously grown out of magical quantum nanobots created by the Singularity the second the brain in the vat scenario occurs and avoid any of the hard questions raised about becoming a brain in a vat in the first place.

Since none of that is likely to happen here in the real world, ever, it makes far more sense to take a hard science approach based on what is known to be at least theoretically possible today.

Brains-in-vats have only ever been science fiction. Regardless, there's nothing about anything I've said that is known to violate any laws of physics, so your objection to 'magical' extrapolations is irrelevant. I say "The Matrix", but obviously you can substitute any number less fanciful mechanisms into the process -- psychotropic drugs & electromagnetic stimulation are not fiction.