I'm not sure thinking or self awareness stops when you're asleep. What about when you dream, are you not aware of a self when you recall that dream? Who is the dream happening to? What about lucid dreamers who are able to control their surroundings and actions whilst in the dream state.

I think in sleeping we enter different states of consiousness which are, perhaps, no less real than the waking consiousness. In deep, non REM (rapid eye movement) sleep, when dreaming has been found to not occur maybe you are correct. There could indeed be loss of self awareness and verbal thinking in this deep sleep state. Note that the left side of the brain is predominantly involved with the processing of language, logic and verbal thought. However the right side of the brain responds to music, emotion, creativity, art and a whole of host of other traits which aren't easily communicated through words. In meditation it can be found that by limiting the power of words and thoughts over your consciousness you can indeed escape the concept of self and simply have pure awareness. Further, it becomes apparent that pure selfless consciousness/ awareness is a fundamental property of the universe and the waking reality is actually just a secondary illusion!

In lucid dreams you're not asleep, you're awake and thus the qualification "lucid". If memory serves they are states in which a person becomes aware that fae is dreaming which is basically an instance of the general pattern of how a sense of self/I forms viz. to infer a thinker from the act of thinking which here is dreaming. Also, if, as you, seem to be suggesting, the self/I persists in sleep, where does it go when we're in non-REM phases of sleep? In these phases the brain is simply not processing any information that can enable us to be aware of thinking at all; no sensory data processing and no sense-independent cogitations and so the two ways by which a person may become aware of a self/I are unavailable. Ergo, we return to my original conclusion that there is no self/I without thinking and this applies with full force to sleep, at least the non-REM phases of it.

It maybe tempting to say that the self/I is distinct from the brain, currently the main protagonist in this tale of thought & thinking, but this is not logically entailed by the facts at hand viz. thinking and the awareness of it. Self-awareness, the critical phenomenon here, could simply be the brain perceiving itself through the medium of thought.

Lucid dreaming does by definition requires that you be asleep, and not awake. You can't be awake and be dreaming at the same time.

1. All thinking ceases

2. The impression of a self/I is lost — TheMadFool

Right off dreams are a clear exception to this - not all dreams but in most there is a sense of an I and also there is often recall. I actually think it is a different sense of self, but still a sense of self. I feel, for example, upon waking that I have been very relaxed for a long time - if I slept through the night, and needed what I experienced. Not just 'I am rested now' but what a pleasant time I've been having for a long period of time.

How do we know because when we wake up we don't recall anything that contradicts both 1 and 2 (we don't remember thinking and being aware of a self) and recall is a widely accepted necessary property to conclude thinking was ongoing and self-awareness was present. — TheMadFool

It's possible that it is widely accepted by I don't think it's a necessary criterion. People can experience things and be conscious but not remember them - this can happen on some dentistry pain medications. IOW one can be experiencing but not recording the experiences in the same way one does while awake. I'd just like to throw in that one can also connect to the conscousness in non-dream sleep - IOW be lucid in this also AND have recall. Meditation after long periods can do this and likely there are other techniques, perhaps more directed. I have experienced this state fairly often. It is quite different from waking states. My mind is blank of verbal thoughts. It is very grounded in the body. I often hear myself snoring. Sometimes I wake up, because it can be a bit exciting. Sometimes I drift back to non-lucid states or dreams.

There are competing interpretations within ancient contemplative traditions of what happens during non-rem sleep. Some have argued that there is no thinking going on, whereas others schools have claimed that one maintains an awareness even during non-rem sleep. The philosopher of mind and cognitive neuroscientist Evan Thompson favors the view that awareness persists through deep sleep and he has devised some fascinating studies to demonstrate this.

Dreamless Sleep, the Embodied Mind,and Consciousness The Relevance of a Classical Indian Debate to Cognitive Science

Lucid dreaming does by definition requires that you be asleep, and not awake. You can't be awake and be dreaming at the same time. — Pantagruel

Right off dreams are a clear exception to this - not all dreams but in most there is a sense of an I and also there is often recall — Coben

It's possible that it is widely accepted by I don't think it's a necessary criterion. People can experience things and be conscious but not remember them - this can happen on some dentistry pain medications. IOW one can be experiencing but not recording the experiences in the same way one does while awake. — Coben

There are two parts to lucid dreaming: (1)the dream and (2) awareness (of the self/I dreaming).

Ordinary dreaming is simply (1) the dream and (3) variable recall of the dream if awakened at the appropriate time or if the dreams were exceptional in some way, etc.

Neurobiologically, dreams are a sleep phase called REM sleep and in this sleep stage brain activity purportedly resembles an awakened state of mind. Insofar as it concerns me, the most crucial aspect of dreams is that there is thinking going on.

Here I'd like to distinguish the self/I from the sense of self/I. The self/I is simply the thinker but the sense of self/I is an inference: thinking is occuring; ergo something is thinking and that something is me. Since dreams are thoughts, there is a thinker, the self/I, but only in lucid dreams does the inference to a sense of self/I develop. How is this relevant? Well, it shows that dreams evidence the existence of a self/I even without a sense of self/I: dreams = thoughts; thoughts -> thinker (self/I). Nevertheless this conclusion is restricted to the dream/REM phase of sleep.

What about non-REM sleep where there is a complete cessation of all thought, including dreams. From a materialistic perspective, if the thinker (self/I) is equated to the physical brain, then it's possible to say, since nothing happens to the brain except a change in its level of activity, that the self/I, considered as the brain, continues throughout all phases of sleep and waking. However, this is unsatisfactory because I sense a general disposition in people, everyone in fact, towards a belief that the self/I is more about the function of the brain than the material form of the brain i.e. they'll probably reject the claim that the self/I = brain. If so, then the only other place for the self/I to exist is in the domain of brain function (thought) and that would lead us to the conclusion that the self/I would perish along with the death of the brain. After all no brain, no brain function; no brain function, no self/I

As for the question of the relevance of memory to the self/I (the thinker) it may appear that, since we don't remember many waking activities and dreams despite having experienced them, memory isn't relevant to the self/I as the one that experiences them. However, how does one distinguish between what the self/I experienced and didn't experience? Memory right? There's no other method, apart from memory, to make this distinction. Granted that memory isn't perfect and even what was experienced may become something never experienced (memory failure) but as it stands, memory remains the only tool in our bag to know what experience we were part of and what experience we weren't a part of. Basically the experiences recalled by the self/I are categorically those in which the, pertinent herein, self/I existed and those experiences not recalled maybe either experiences in which the self/I didn't exist or an instance of memory failure. As you can see, the only information on experience the self/I can be sure of is when it remembers that experience. Instances of the self/I failing to remember can be due to either memory failure or, as it concerns this discussion, nonexistence of the self/I during that time.

Well, let's look closely at the problem: if the self/I doesn't recall an experience than either the self/I didn't exist or the self/I existed but fails to remember. Let's begin by asking how we come to realize that these two are possibilities that we have to consider? That a failure to remember is due to the nonexistence of the self/I is easily understandable for if the self/I didn't exist then the question of experience of anything at all doesn't arise: nothing that experiences; ergo no question of experience or the memory of it.

The next possibility, that the self/I did experience but fails to recall, is interesting to say the least. Surely, it is a position inferred to from some evidence. What is this evidence? If you ask me there are two pieces of information required for this: 1) no recall of an event by the self/I and 2) evidence that the self/I did experience that event. Take a person X and a week in faers life to help us understand this. X decides on Sunday 2:00 PM to remember the week that went by. If fae is anything like me then fae will not actually fail completely in remembering the the week that's gone by: fae may forget what fae ate, who fae talked to, what the talk was about, where fae went, what time fae did that, etc. BUT fae will remember that fae was awake and asleep, maybe even dreamed when fae was asleep and it's this memory of being awake and intermittently asleep, that serves as evidence for X believing that sometimes X doesn't recall experiences that the X had. In other words the knowledge that sometimes we don't remember what we experience is based on memory of being awake/asleep and present during that experience. Ergo, memory is necessary to infer that thinking occurred or that there was a self/I.

Some have argued that there is no thinking going on, whereas others schools have claimed that one maintains an awareness even during non-rem sleep. The philosopher of mind and cognitive neuroscientist Evan Thompson favors the view that awareness persists through deep sleep and he has devised some fascinating studies to demonstrate this. — Joshs

Thanks for the link.