When an honest man discovers he is mistaken, he will either cease being mistaken, or cease being honest.
I do not pretend to know where many ignorant men are sure; that is all that agnosticism means.
Education costs money, but then so does ignorance.
Nothing in life is to be feared, it is only to be understood. Now is the time to understand more, so that we may fear less.
If a nation expects to be ignorant and free, in a state of civilization, it expects what never was and never will be.
There is a principle...which cannot fail to keep a man in everlasting ignorance. This principle is, contempt prior to examination.