Thanks for your really interesting reply, archie. Great point about the voices of the gods!
LSD, back in the day, was an eye- and mind-opening experience, wasn't it?! I was too young and fucked-up then to understand my trips as I do now but, later on, they've greatly enhanced my insight into myself and, more generally, the psychologies of perception. It would be lovely if I could always see every glowing shade of green in a tree, without chemical assistance - but still nice to know I'm capable of it! Oh, and seeing music! Am quite envious of synaesthetics.
My question about clairvoyance came from this: If time is linear, as it's assumed to be (below the speed of light, anyway) then it's impossible to know what will happen in the future - unless you accept pre-ordination, which I can't do. Scientists aren't sure time is linear, though; it might be flowing, with whorls and eddies, or it might not actually exist other than as a useful concept. If there are eddies in time, or there is no time (everything's always happening at once) then clairvoyance could be possible. Not that I care much, tbh; it's just interesting.