confutatis said:
I'm not rejecting the claims that people experience enlightenment, far from it. I know the brain/mind is capable of producing anything imaginable, and quite a few things unimaginable. But I do reject most metaphysical claims associated with altered states of mind.
I don't reject them, but I don't accept them. I prefer to take a position of agnosticism with regards to the more extravagent metaphysical truths purportedly revealed in altered states of consciousness. Please keep this in mind when considering my responses to your ideas.
Also, I prefer to use the term "spiritual experience," or SE, in the following discussion instead of enlightenment. Enlightenment can be understood loosely as a special case (indefinitely enduring, with perhaps some additional qualitative constraints) of the more general concept of spiritual experience. As the discussion here has been carried out on a very foundational, general level, it is more appropriate to use the more basic underlying concept.
Why does that make sense to you? It doesn't make any sense to me. When these people describe their altered states of consciousness, they do so from quite an ordinary state. If what they discover in the ASC makes any sense in the baseline state, it can be known from the baseline state - no "trips" required. And if it doesn't make sense in the ordinary state... well, then it doesn't make sense.
I can have a conceptual understanding of what it is like to dream from my baseline, waking state. At the same time, I would not expect someone to have an understanding of dreaming as good as mine if that person had never experienced a dream before. They could get some sort of conceptual understanding from verbal descriptions of dreams, but I take it as uncontroversial that such a person would achieve a much better understanding of what it is like to be in a dreaming state if that person eventually did experience a dream firsthand.
You can substitute any altered state of consciousness in for "dream" in the above paragraph, including "spiritual experience," and it would remain just as valid. Dreaming consciousness is a particular kind of ASC, and is useful for the purposes of this discussion since it's undoubtedly the most widely experienced ASC there is. Epistemological and metaphysical claims about spiritual experiences can be clarified by testing analogous claims about dreaming.
As far as I know, the idea of "enlightenment" is a key point of some religions. It is a belief, not unlike the concept of salvation in Christianity. I'm not saying one or both ideas are false, but I think it's very reasonable to think of them as rough approximations of truths beyond our current ability to understand.
Spiritual experience is more than belief. It is a particular kind of state of consciousness that viscerally feels different from normal waking consciousness in a completely novel way, similarly to how dreaming viscerally feels different from waking consciousness on so many levels. People over the ages have attached metaphysical meaning (belief structures) to such experiences, but those belief structures do not constitute the essence of the term. They are scaffolds built on top of the central conceptual structure, which is simply about the experience itself. The aborigines constructed a metaphysical belief structure based on their experiences with dreaming consciousness, but that does not mean that dreaming can be exhaustively characterized by those beliefs or other metaphysical beliefs derived from dreaming. The core concept of what an SE is is no more and no less a belief than is the concept of the experiential "what-it-is-like-ness" of dreams.
There's no rationale to doubt that the sun exists, when it can be seen everyday by everyone, but it took centuries for us to learn that the sun is a star. Now look at Les' last post and his "background" - what the heck is that, and how does he know it is what he thinks it is? How does he know he's not mistaken it for some completely unrelated phenomenon, just like the ancients mistook the sun for some god in the sky?
This is a great paradigm case to clear up some of the confusion going on here. I know what Les was referring to, having experienced similar things myself. It is important to recognize that at its core, this claim of a 'background' is not a metaphysical claim, but that it is an experiential claim; that is, it's not
immediately a claim about the true 'nature' of a phenomenon underlying a certain appearance, it's just a claim about the existence and nature of a certain appearance as such. Les has extended metaphysical claims on the basis of this experiential claim, but I need not agree with his metaphysical claim in order to recognize a ring of truth in the experiential claim by way of comparison to my own experiences.
Using your sun example, the ancients and modern scientists certainly have different metaphysical claims about what the sun is. But both agree rather plainly on the experiential aspect-- that the sun's appearance is simply that of a bright yellow disc. Whether you think the sun is an anthropomorphic god or a collection of vibrating molecules, you can agree rather uncontroversially about the experiential claim, assuming you have a normally functioning visual system. I suspect you have trouble identifying with the experiential claim of a certain background state of consciousness in the same way a person who has never seen bright things or yellow things has trouble in identifying with the experiential claim that the sun is a bright yellow disc.
The other day I was lying in bed, very tired, when I had the most unusual experience - my mind became completely devoid of any thoughts, yet I didn't lose consciousness (I may have told this story before; anyway...) So I'm in my bed thinking, "isn't this strange? I'm not thinking about anything". During the few seconds the experience lasted, I was in awe of contemplanting a void mind, something I never experienced before, or after. But when it was over I was a bit confused: how could I not be thinking about anything when I was thinking about "not thinking about anything"? That doesn't make any sense. Something strange definitely happened, but it's not what I thought it was.
Perhaps your mind really was devoid of thought up until the point where you recited this thought to yourself? Surely there was some temporal extension to the experience, one part of which was thoughtless, and the other part of which contained thoughts about the thoughtlessness of the preceding portion.
I don't think it's a possibility. If drugs really helped anyone understand things better, they could help people achieve ordinary things. Drugs could help people find solutions to complex differential equations, compose beautiful symphonies, design awesome buildings, write breathtaking poetry, and so on. As it turns out, at best drugs do absolutely nothing in that sense, and at worst they render a person insane. I find the claim that drugs open one's mind to really, really important truths, while doing absolutely nothing for more mundane things, to be unbelievably naive.
If you think drugs (or more generally, exceptional states of consciousness which may be accessed either by drugs or other means) have never assisted anyone in writing exceptional poetry or composing exceptional music, boy are you kidding yourself.

Many great poets did their best work when in trance-like or 'transcendental' states of consciousness. Whole religions have been founded on the altered states of consciousness of 'enlightened' spiritual leaders or 'visionary' prophets. The revolutionary music of the 60s and 70s owes much of its soul to marijuana and psychedelics. (Just ask Bob Dylan or the Beatles or Pink Floyd or Jimi Hendrix, to name a few-- I highly doubt the Beatles would have ever composed Revolver or Sgt Pepper in the absence of these experiences.) Dali and Van Gogh, to name a couple of highly influential and praised visual artists, owe much of their creative talent to their peculiar states of consciousness. Personally, I dabble in creating art and poetry, and some of what I consider to be my best stuff has come directly from altered states. (Others have come to the same conclusions without knowing anything about how they were created.)
I don't think the SE state is optimal for straightforward logical tasks like performing math. But they are great enhancers for social and artistic intelligence, or social and artistic sensibility if you prefer.
"Turning the mind off" means going unconscious, which is not what those people claim. They claim they are fully conscious, but not conscious of anything. This doesn't make any sense. I think they are just fooling themselves, and the fact that I can also fool myself if I do whatever it is that they do proves absolutely nothing.
It doesn't make sense that the speed of light is constant in all reference frames either. Whether consciousness can exist in the absence of recognizable contents of consciousness is ultimately an empirical question that may be answered on a firsthand basis, eg by using the appropriate meditational techniques (I don't believe any known drugs can simulate this kind of experience).