But before mankind could be ripe for a science which takes in the whole of reality, a second fundamental truth was needed, which only became common property among philosophers with the advent of Kepler and Galileo. Pure logical thinking cannot yield us any knowledge of the empirical world; all knowledge of reality starts form experience and ends in it. Propositions arrived at by purely logical means are completely empty as regards reality. Because Galileo saw this, and particularly because he drummed it into the scientific world, he is the father of modern physics -- indeed, of modern science altogether. (Albert Einstein, Ideas and Opinions)

Galileo had already made a significant beginning toward a knowledge of the law of motion. He discovered the law of inertia and the law of bodies falling freely in the gravitational field of the earth. (Albert Einstein, Ideas and Opinions)

"Alas, you find [vanity] in so many scientists! It has always pained me that Galileo did not acknowledge the work of Kepler." To I. Bernard Cohen, April 1955, in an interview shortly before his death. Scientific American, July 1955, 69