Cheers for M. Ted's clarity, and ditto to what he said; "great thoughts" is the most obscure issue but one of the most important ones on a a songwriter's plate -- not necessarily philosophical but greatly human will do.
Look at the wonderful string of curses in "Nell Flaherty's Drake". That...to my mind...is great song-writing even though it is about an ordinary, even petty but intense human desire. The important thing is finding the perspective that will be important in human terms, because that is where your song will find traction. Great human thoughts surface in the most ordinary blues music, for example -- "a ten dollah woman, latchin on to a 2-dollar man" comes to mind.
Being able to say a lot with few words is certainly part of that side of things as well.