Give unqualified assent to no propositions but those the truth of which is so clear and distinct that they cannot be doubted. The enunciation of this first great commandment of science consecrated doubt.

Some experience of popular lecturing had convinced me that the necessity of making things plain to uninstructed people, was one of the very best means of clearing up the obscure corners in one's own mind.

Science has fulfilled her function when she has ascertained and enunciated truth.

I hated tobacco. I could have almost lent my support to any institution that had for its object the putting of tobacco smokers to death...I now feel that smoking in moderation is a comfortable and laudable practice, and is productive of good. There is no more harm in a pipe than in a cup of tea. You may poison yourself by drinking too much green tea, and kill yourself by eating too many beefsteaks. For my part, I consider that tobacco, in moderation, is a sweetener and equalizer of the temper.

We are prone to see what lies behind our eyes, rather than what apprears before them.

Teach a child what is wise, that is morality. Teach him what is wise and beautiful, that is religion!

Economy does not lie in sparing money, but in spending it wisely.