Proof by assertion, sometimes informally referred to as proof by repeated assertion, is an informal fallacy in which a proposition is repeatedly restated regardless of contradiction and refutation. Sometimes, this may be repeated until challenges dry up, at which point it is asserted as fact due to its not being contradicted (argumentum ad nauseam). In other cases, its repetition may be cited as evidence of its truth, in a variant of the appeal to authority or appeal to belief fallacies.
This fallacy is sometimes used as a form of rhetoric by politicians, or during a debate as a filibuster. In its extreme form, it can also be a form of brainwashing. Modern politics contains many examples of proofs by assertion. This practice can be observed in the use of political slogans, and the distribution of "talking points", which are collections of short phrases that are issued to members of modern political parties for recitation to achieve maximum message repetition. The technique is also sometimes used in advertising.
- Austin J. Freeley, David L. Steinberg, Argumentation and Debate; Critical Thinking for Reasoned Decision Making (Wadsworth Cengage Learning, Boston, 2009), p. 196
- Forensic Science and Law, ed. Cyril H. Wecht, John T. Rago (CRC Press, Boca Raton, 2006), p. 32
- "Philosophy in Action: Logical Fallacies on Philosophy in Action". Philosophy in Action. Retrieved 2017-02-17.
- Robert Ruxton, 'Selling by the Printed Word', The Printing Art, Vol. xxxix (Cambridge: Cambridge University Press, 1922), p. 60