Credo quia absurdum is a Latin phrase that means "I believe because it is absurd", originally misattributed to Tertullian in his De Carne Christi.
Early modern, Protestant and Enlightenment rhetoric against Catholicism and religion more broadly resulted in this phrase being changed to "I believe because it is absurd", displaced from its original anti-Marcionite context into a personally religious one.
[1] Tertullian's phrase originated in a rebuttal to Marcion's view that a human death for the divine Son of God would be paradoxical and thus ought to be rejected.
[17] According to Peter Harrison, the first time that the maxim was quoted was in Thomas Browne's highly influential religious classic Religio Medici (The Religion of a Doctor) of 1643, ensuring that the maxim received a wide audience at this time, and Browne also shifted the context of Tertullian's phrase from a discourse against Marcion to personal faith, and also shifted the wording of the phrase from its original certum est, quia impossibile ("It is certain, because it is impossible") to "I believe, because it is impossible.
"[1] Many of Browne's contemporaries criticized him and Tertullian for this maxim, including Henry More, Edward Stillingfleet, Robert Boyle, and John Locke.
The maxim was then brought to a French audience through Pierre Bayle's highly influential 1697 Dictionnaire Historique et Critique, which catalogued controversies of philosophical and religious nature as well as historical events and persons related to them.
[18] The maxim would continue to be attributed to Augustine until Gaston de Flotte noted the original Latin and misattribution by Voltaire, however, the rhetorical appeal of the maxim was great enough that it continued to be widely used, even to the present day,[1] including being used by figures like Sigmund Freud, Ernst Cassirer, Max Weber, Richard Dawkins, Jerry Coyne and even Simon Blackburn's Oxford Dictionary of Philosophy.
"[21] The phrase is thus sometimes associated with the doctrine of fideism, that is, "a system of philosophy or an attitude of mind, which, denying the power of unaided human reason to reach certitude, affirms that the fundamental act of human knowledge consists in an act of faith, and the supreme criterion of certitude is authority" according to the 1913 Catholic Encyclopedia, which later states, "It is not surprising, therefore, that the Church has condemned such doctrines".