reason
“Justice without force is powerless; force without justice is tyrannical.”
“Man is but a reed, the most feeble thing in nature; but he is a thinking reed.”
“The heart has its reasons which reason knows nothing of.”
“Poetry heals the wounds inflicted by reason.”
“Facts are facts and will not disappear on account of your likes.”
“Immaturity is the inability to use one's understanding without guidance from another.”
“The world is divided into men who have a religion and no reason and men who have reason and no religion.”
“Truth does not contradict truth.”
“The beginning of wisdom is to call things by their right names.”
“The rules of morality are not the conclusions of our reason.”
“A wise man proportions his belief to the evidence.”
“Only when our clever brain and our human heart work together can we achieve our full potential.”
“It is a capital mistake to theorize before one has data.”
“Divide each difficulty into as many parts as is feasible and necessary to resolve it.”
“Cogito, ergo sum.”