This will be a short article. I've been seeing a lot of dubious reasoning about consciousness and sleep. One famous problem is the problem of personal identity with a destructive teleporter. In this problem, we imagine that you are cloned perfectly in an alternate location and then your body is destroyed. The question asked is whether this clone is the same person as you.
One really bad argument that I've seen around this is the notion that the fact that we sleep every night means that we experience this teleporter every day.
The reason why this is a very bad argument is that it equivocates with two different meanings of consciousness:
- Consciousness as opposed to being asleep or unconscious, where certain brain functions are inactive
- Consciousness as opposed to being non-sentient, like a rock or bacteria, where you lack the ability to have experiences
During some periods of sleep. So far as I am aware, in deep sleep there's no reason to think you are having any experiences at all.
Anyway, for those who don't object to thought experiments: imagine that there's some machine that completely suspends all your brain activity for five minutes, after which it continues from exactly its previous state. Are you the same person after as before? If you answer yes to this -- which I bet almost everyone does -- then the implications are the same as those you'd get from sleep involving a complete cessation of consciousness.
For 5 minutes suspension versus dreamless deep sleep - almost exactly the same person. For 3 hours dreamless deep sleep I'm not so sure. I think my brain does something to change state while I'm deep asleep, even if I don't consciously experience or remember anything. Have you ever woken up feeling different about something, or with a solution to a problem you were thinking about as you dropped off ? If that's not all due to dreaming, then you must be evolving at least slightly while completely unconscious.