Reason,
Observation, and Experience -- the Holy Trinity of Science. - Robert
G. Ingersoll
You can observe a lot just by watching. - Yogi Berra
To him that watches, everything is revealed. - Italian Proverb
Nothing has such power to broaden the mind as the ability to
investigate systematically and truly all that comes under thy
observation in life. - Marcus Aurelius
He alone is an acute observer, who can observe minutely without
being observed. - Johann Kaspar Lavater