Thinking in its lower grades is comparable to paper money, and in its higher forms it is a kind of poetry. – Havelock Ellis, The Dance of Life, 1923

Physiological response to thinking and to pain is the same; and man is not given to hurting himself. – Martin H. Fischer (1879–1962)

Practical gentlemen hate uncertainty, balancing of probabilities, skepticism or approximation. They have a number of bitterly satirical comments on persons whose minds are so open that their brains fall out. They are bent on getting to a conclusion. – Max Radin, 1937