What goes up must come down. - Isaac Newton

"Errors are not in the art but in the artificers."

"Les hommes construisent trop de murs et pas assez de ponts."

"Tact is the art of making a point without making an enemy."

"I can calculate the motion of heavenly bodies but not the madness of people."

"Gravity explains the motions of the planets, but it cannot explain who sets the planets in motion."