Robert Ingersoll was humorist, iconoclast and lover of humanity.
It is said that the difference between man and the lower animals is that man has the ability to laugh.
When you laugh you relax, and when you relax you give freedom to muscles, nerves and brain-cells. Man seldom has use of his reason when his brain is tense. The sense of humor makes a condition where reason can act.
Ingersoll knew that he must make his appeal to man's brain.

Introduction. - An American Bible (1912)