I don't agree there's more to it than random firings, but only in the sense they aren't quite random at all. For the rest I do still think there's nothing more to it than that. The biochemistry behind psychedelics is fairly well-researched and can be explained, so while there is a random component to it just like there are variations in, say, how people perceive color, I do still belive that's really all there is to it, just hallucinations (both sensory and mentally). No matter how in touch one might feel with whatever mystic stuff out there, no matter how profound it might feel, I've yet to see any evidence whatsoever of that somehow proving there effectively is something out there. Doesn't matter those feelings are very real, but it's just.. feelings.