"Reason, observation, and experience the holy trinity of science."
"Life can only be understood backwards but it must be lived forwards."Robert Green Ingersoll on Soren Kierkegaard
"The only source of knowledge is experience."Robert Green Ingersoll on Albert Einstein
"Experience: that most brutal of teachers. But you learn, my God do you learn."Robert Green Ingersoll on C. S. Lewis
"Experience is simply the name we give our mistakes."Robert Green Ingersoll on Oscar Wilde
"A man who carries a cat by the tail learns something he can learn in no other way."Robert Green Ingersoll on Mark Twain
"It is a blessed thing that in every age some one has had the individuality enough and courage enough to stand by his own convictions."
"Anger is a wind which blows out the lamp of the mind."
"Let us put theology out of religion. Theology has always sent the worst to heaven, the best to hell."
"The greatest test of courage on earth is to bear defeat without losing heart."
"We need men with moral courage to speak and write their real thoughts, and to stand by their convictions, even to the very death."