Mental slavery is mental death, and every man who has given up his intellectual freedom is the living coffin of his dead soul. – Robert Ingersoll, Individuality

Our wretched species is so made that those who walk on the well-trodden path always throw stones at those who are showing a new road. – Voltaire

The fatal tendency of mankind to leave off thinking about a thing when it is no longer doubtful, is the cause of half their errors. – John Stuart Mill