Clarke's Three Laws.
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.
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.
Arthur C Clarke - "Hazards of Prophecy: The Failure of Imagination", in Profiles of the Future (1962)