“The fountain of content must spring up in the mind, and he who hath so little knowledge of human nature as to seek happiness by changing anything but his own disposition, will waste his life in fruitless efforts and multiply the grief he proposes to remove.”

“He who has so little knowledge of human nature as to seek happiness by changing anything but his own dispositions will waste his life in fruitless efforts and multiply the griefs which he purposes to remove”

“He was a vegetable, so trying to change his mind was fruitless.”

“Man's mind is his basic tool of survival. Life is given to him, survival is not. His body is given to him, its sustenance is not. His mind is given to him, its content is not. To remain alive, he must act, and before he can act he must know the nature and purpose of his action. He cannot obtain his food without a knowledge of food and of the way to obtain it. He cannot dig a ditch-or build a cyclotron-without a knowledge of his aim and of the means to achieve it. To remain alive, he must think”

“The truth is that life is hard and dangerous; that he who seeks his own happiness does not find it; that he who is weak must suffer; that he who demands love will be disappointed; that he who is greedy will not be fed; that he who seeks peace will find strife; that truth is only for the brave; that joy is only for him who does not fear to be alone; that life is only for the one who is not afraid to die.”

“The seeker after truth is not one who studies the writings of the ancients and, following his natural disposition, puts his trust in them," the first scientist wrote, "but rather the one who suspects his faith in them and questions what he gathers from them, the one who submits to argument and demonstration and not the sayings of human beings whose nature is fraught with all kinds of imperfection and deficiency. Thus the duty of the man who investigates the writings of scientists, if learning the truth is his goal, is to make himself an enemy of all that he reads, and, applying his mind to the core and margins of of its content, attack it from every side. he should also suspect himself as he performs his critical examination of it, so that he may avoid falling into either prejudice or leniency.”