Well back to the original question...my input is that I think it is irrelevant in the end whether the experience is physiological or psychological or whatever...what's important is the ability of serotonin mimicking drugs especially to act as 'messengers' if you will...which scientifically speaking they do actually do this, though it is up to us as human beings to interpret the messages and make the experience profound.
It seems to be that the nature of human consciousness and language is based off of these serotogenic systems especially, but also many other chemicals and physiological functions within our nervous system and brain. And as some of you have mentioned, it is precisely this language that limits us in our ability to express ourselves....and in many ways language seems to work against us because in the western cartesian world of understanding it seems that the psychedelic experience is nothing more than 'physiology'...and "a bunch of chemicals"....we'll we shouldn't be so quick to assume that these chemicals like serotonin are lifeless mundane entities....because when we look at the bigger picture these chemicals are basically the building blocks of life...or at least they are the building blocks of human consciousness...and play an integeral role in nature, bridging the gap between plants, humans, and animals.
But I think there is a lot still to be learned about the connections between human consciousness and biochemistry....but we shouldn't assume that therefore the psychedelic experience is somehow less authentic or 'supernatural'...because these are cultural constructions that get in the way of what's actually important about the psychedelic experience.
Essentially I think psychedelics exist for a reason, plants (the natural masters of chemistry) in a sense use human beings as extensions...when you look at the human brain you see it is hardwired with particular receptors that have high affinity to certain substances (namely tryptamines, cannabinoids, opioids etc etc)...these substances all carry very different effects profiles, but share in common the fact that they elicit various behaviours which have profound ramifications in the human universe...how humans interact in the global scheme of things.
So I think the plants are definatley here to tell us something (using chemicals as messengers)...we as humans seem to be the most complex medium through which mother nature has expressed her self as of yet (at least it seems that way from our perspective). But plants may be equally as complex as we are...just in a different way.
I guess the moral of my post is really that it can be tempting to try and categorize the psychedelic experience as just a "drug induced experience"...it can be so overwhelming that we might think "oh, it's all just the effects of a drug..nothing more". But if we set aside our preconceptions...and perhaps take on the demeanor of a young child...we wouldn't be so quick to try and rationalize the experience, but rather just accept it for what it is...or whatever you believe it is. There's no right or wrong, reality is essentially a subjective thing...and that's what the psychedelic experience has brought to the table for me.
Governments of course don't want people to question the nature of their reality too much...so it's natural that the world of conservative rational thinking and following societal norms people would be hostile to the notion of the psychedelic experience...as it forces one to re-think the nature of reality and culture.
Then again, this is just my interpretation of the whole thing....but I genuinely think that psychedelics will play a key role in solving major global social and political conflicts in the future. Essentially the hippies were onto something big, but they got shut down by the military-gov complex....the revolution is just starting back up again, and this time it's here to stay (hopefully)...but I really see a lot of progress in clinical research and personal/spiritual growth....I think western science and aboriginal/indigenous schools of thought can co-exist...it's important not to fall into one school of thought, collaboration really is key in progressing with psychedelics.