“Los hombres construimos demasiados muros y no suficientes puentes.”

“What goes up must come down.”

“If I have seen further it is by standing on the shoulders of Giants.”

“I do not know what I may appear to the world, but to myself I seem to have been only like a boy playing on the sea-shore, and diverting myself in now and then finding a smoother pebble or a prettier shell than ordinary, whilst the great ocean of truth lay all undiscovered before me.”

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

“Tact is the knack of making a point without making an enemy.”

“and to every action there is always an equal and opposite or contrary, reaction”