"It is impossible for a man to be affected by any emotion unless he imagines something which excludes the existence of an external cause of that emotion."

"Freedom is absolutely necessary for the progress in science and the liberal arts."

"The highest activity a human being can attain is learning for understanding, because to understand is to be free."

"I have striven not to laugh at human actions, not to weep at them, nor to hate them, but to understand them."

"Whatsoever is, is in God, and without God nothing can be or be conceived."