1) When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong.I'm not sure if I'm just being unusually dyspeptic at the moment, but these are all striking me as rather egregious pseudo-profundities.
2) The only way of discovering the limits of the possible is to venture a little way past them into the impossible.
3) Any sufficiently advanced technology is indistinguishable from magic.
But then, golden age science fiction's big three (Asimov, Clarke and Heinlein) Clarke is the one who never produced anything I enjoyed. All three were subject to occasional fits of pomposity, but Clarke's novels weren't even enjoyable.