The premise is that the brain is still connected. No explanation as to how, but that's the premise. It is still getting the same information from the body, through whatever unspecified means.

At least that's my interpretation of the premise — Patterner

I am sorry I have no understanding of your opinion that the premise maintains a body/brain connection. I am left with the impression that the argument lacks awareness of what the body has to do with awareness of one's self.

The op says:

He then gives a thought experiment to show this where a man has his brain put in a vat but it is still connected, so his body is moving with out the brain in it. — Lexa

The brain is still connected. I take it that the reason the body is still moving is because the brain is still receiving and sending with the body, as though still in its natural state. But I may be misinterpreting. Difficulty ti know.

The brain is still connected. I take it that the reason the body is still moving is because the brain is still receiving and sending with the body, as though still in its natural state. But I may be misinterpreting. Difficulty ti know. — Patterner

Difficult to conceive, but a wonderful opening for further consideration. How about Socrates and the cave? Just how much can the bodies move and experience life? Can these bodies give each other pleasure or cause each other emotional pain? Can they experience the thrill of discovery or the satisfaction of saving a life? What in the world can give these bodies meaningful lives? Like a dead frog twitches when given an electrical shock but is that equal to living? Of what can that brain be conscious?

How would blacking out be different from sleeping? — Lionino

As I say, I cannot remember how he parses the different states.
An off-the-cuff note, would be that when 'blacked out' memories are not created, and you are not consciously aware. You can do both while sleeping (dreaming and lucid dreaming, particularly).

sort of like identical twins. they are exactly the same until they aren't.

@Tom Storm

If you check episode below ("Does Tuvix Deserve To Die?"Jason expounds on his position at about 46min forward regarding why he doesn't drink, on a Parfitean account of identity
.

Ah, Parfit, I have heard of him. I was told he holds a process philosophy view of self. I am yet to read it, but I don't like the argument that getting drunk kills you because it changes some mental states — by the same argument, going through a break-up makes you die too.
That was the main topic of my first thread.

I think Jason has actually spoken about that - how certain experiences change your mental states to such a degree there might be a change in identity. But, I think you're slightly misapprehending - its not changes, its a discontinuity - i.e, disestablishment->reestablishment that provides the 'death' on his account.
I don't buy it either, ftr.

Parfit has a reductionist account which concludes there is no persistent self, but what matters to morality is psychological continuity only. Hence, Jason's rather bleak and stringent account of death

Parfit has a reductionist account which concludes there is no persistent self, but what matters to morality is psychological continuity only. — AmadeusD

That much I can agree with.

I highly recommend Reasons and Persons (his 1984 tour de force).

From DeepAI (which i've just, in the last 12 hours, started using):

""Reasons and Persons" is a seminal work by philosopher Derek Parfit, exploring ethical theories and the concept of personal identity. Parfit examines how different ethical theories, such as consequentialism and deontology, provide reasons for action and their implications for personal identity. He explores the relevance of these theories to moral choices and the nature of self-interest. Parfit argues for a reductionist view of personal identity, suggesting that psychological continuity and connectedness are more significant than a fixed identity over time. Overall, the book delves into the complex relationship between ethical theories, personal identity, and rational decision-making."

The non-identity problem stems from his work:

"The non-identity problem questions whether there can be harm done to a person by causing their existence to be different, when their alternative existence might include certain advantages. It raises ethical and philosophical questions about how we understand harm and the nature of personal identity."

Thank you. I was looking into reading Parfit but I did not know where to start. I will give it a read when my mind is free. For now, time to eat a fat cheeseburger (which I don't usually do) to release some endorphins (or whatever).