“I esteem myself happy to have as great an ally as you in my search for truth.”

“My dear Kepler, what would you say of the learned here, who, replete with the pertinacity of the asp, have steadfastly refused to cast a glance through the telescope? What shall we make of this? Shall we laugh, or shall we cry?”

“The modern observations deprive all former writers of any authority, since if they had seen what we see, they would have judged as we judge.”

“In the sciences the authority of thousands of opinions is not worth as much as one tiny spark of reason in an individual man.”

“If I were again beginning my studies, I should follow the advice of Plato and start with mathematics, a science which proceeds very cautiously and admits nothing as established until it has been rigidly demonstrated.”

“See now the power of truth; the same experiment which at first glance seemed to show one thing, when more carefully examined, assures us of the contrary.”

“Happiness is the final and perfect fruit of obedience to the laws of life.”

“The highest result of education is tolerance.”

“Example is the best lesson there is.”

“Only a man's character is the real criterion of worth.”

“It isn't enough to talk about peace. One must believe in it. And it isn't enough to believe in it. One must work at it.”

“In the long run, we shape our lives and we shape ourselves. The process never ends until we die. And the choices we make are ultimately our own responsibility.”