Trust a witness in all matters in which neither his self-interest, his passions, his prejudices, nor the love of the marvellous is strongly concerned. When they are involved, require corroborative evidence in exact proportion to the contravention of probability by the thing testified.

Not only do I disbelieve in the need for compensation, but I believe that the seeking for rewards and punishments out of this lifeleads men to a ruinous ignorance of the fact that their inevitable rewards and punishments are here.

Learn what is true in order to do what is right.

The dogma of the infallibility of the Bible is no more self-evident than is that of the infallibility of the popes.

If a little knowledge is dangerous, where is the man who has so much as to be out of danger?

Follow humbly wherever and to whatever abyss Nature leads, or you shall learn nothing.

The only people, scientific or other, who never make mistakes are those who do nothing.