Mathematical discoveries, small or great are never born of spontaneous generation.
Just as houses are made of stones, so is science made of facts.
Geometry is the art of correct reasoning from incorrectly drawn figures.
Guessing before proving! Need I remind you that it is so that all important discoveries have been made?
If we knew exactly the laws of nature and the situation of the universe at the initial moment, we could predict exactly the situation of the same universe at a succeeding moment.
Most striking at first is the appearance of sudden illumination, a manifest sign of long unconscious prior work.