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.

Only one absolute certainty is possible to man, namely that at any given moment the feeling which he has exists.

Every great advance in natural knowledge has involved the absolute rejection of authority.

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

Science is nothing, but trained and organized common sense.

People never will recollect that mere learning and mere cleverness are of next to no value in life, while energy and intellectual grip, the things that are inborn and cannot be taught, are everything.

Friendship involves many things but, above all the power of going outside oneself and appreciating what is noble and loving in another.