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.

To persons uninstructed in natural history, their country or seaside stroll is a walk through a gallery filled with wonderful works of art, nine-tenths of which have their faces turned to the wall.

It is a popular delusion that the scientific enquirer is under an obligation not to go beyond generalisation of observed facts...but anyone who is practically acquainted with scientific work is aware that those who refuse to go beyond the facts, rarely get as far.

I took thought, and invented what I conceived to be the appropriate title of 'agnostic'.

Logical consequences are the scarecrows of fools and the beacons of wise men.

The great thing in the world is not so much to seek happiness as to earn peace and self-respect.

A man who speaks out honestly and fearlessly that which he knows, and that which he believes, will always enlist the good will and the respect, however much he may fail in winning the assent, of his fellow men.