incidentally, my current thought on jhanas is: cool, but useless.. except to the extent to which seeing cool new things is useful, which maybe it is.. is it "useful" to see a magic-eye? It's inspiring.. it's useful to be inspired I suppose.. and jhanas are quite a bit stranger and more interesting than seeing a magic-eye, especially if one has never experienced an altered state of consciousness, I suppose..
..but I don't think anyone walks around all day in a jhana — they're pleasant, but tiring in their own way, and I don't feel "smarter" in a jhana, though I think my thinking is subtly altered.. not sure..
I'm not even sure that being in jhanas is strengthening any mental muscles, aside from those used to enter jhana states. But I'm not even sure they help me focus.. which is ironic since they are states of intense focus..
..maybe I should try entering a jhana state focussing on a particular problem.. though it seems like only the first two would even keep my attention on that problem, and even then they'd just be looking at it, I'm not sure I'd be thinking it through. I suppose it's worth a try.
what the hell are these states? why are they there?
update: I recall now my teacher friend saying that jhana states are pleasurable, and I think they can be very pleasurable, though for some reason my mind doesn't care about that aspect so much, but I have had a pleasurable body-encompassing tingle in a jhana state — I think the fourth.