I believe there exists, & I feel within me, an instinct for the truth, or knowledge or discovery, of something of the same nature as the instinct of virtue, & that our having such an instinct is reason enough for scientific researches without any practical results ever ensuing from them.

The libraries of America are and must ever remain the home of free and inquiring minds. To them, our citizens - of all ages and races, of all creeds and persuasions - must be able to turn with clear confidence that there they can freely seek the whole truth, unvarnished by fashion and uncompromised by expediency.

Books are infinite in number and time is short. The secret of knowledge is to take what is essential. Take that and try to live up to it.

All that I know is nothing - I'm not even sure of that.

You never know a line is crooked unless you have a straight one to put next to it.

You don't know what you don't know.