(more links added as I remember them)

"In theory there is no difference between theory and practice.  In practice there is."
-- Yogi Berra

"I hear and I forget. I see and I remember. I do and I understand."
-- Confucius

"Science is facts. Just as houses are made of stones, so is science made of facts.
But a pile of stones is not a house and a collection of facts is not necessarily science."
-- Jules Henri Poincaré, (1854-1912),
    French scientist, author