When a fact can be demonstrated, force is unnecessary; when it cannot be demonstrated, an appeal to force is infamous. In the presence of the unknown all have an equal right to think.

Robert Green Ingersoll (1833-1899) American lawyer, freethinker, orator

Lecture (1873-12) “Individuality,” Chicago Free Religious Society
    (Source)

Full title "Arraignment of the Church and a Plea for Individuality." Collected in The Gods and Other Lectures (1876).