Credo quia absurdum
Credo quia absurdum is a Latin phrase that means "I believe because it is absurd." It is a paraphrase of a statement in Tertullian's work De Carne Christi, "prorsus credibile est, quia ineptum est", which can be translated: "it is by all means to be believed, because it is absurd". The context is a defence of the tenets of orthodox Christianity against docetism:
- Crucifixus est Dei Filius, non pudet, quia pudendum est;
- et mortuus est Dei Filius, prorsus credibile est, quia ineptum est;
- et sepultus resurrexit, certum est, quia impossibile.
- — (De Carne Christi V, 4)
- "The Son of God was crucified: there is no shame, because it is shameful.
- And the Son of God died: it is by all means to be believed, because it is absurd.
- And, buried, He rose again: it is certain, because impossible."
The phrase does not express the Catholic Faith, as explained by Pope Benedict XVI: "The Catholic Tradition, from the outset, rejected the so-called “fideism”, which is the desire to believe against reason. Credo quia absurdum (I believe because it is absurd) is not a formula that interprets the Catholic faith."
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."(Catholic Encyclopedia). It has also been used, though often in different interpretations, by some existentialists.
The phrase inspired a celebrated bon mot by H.L. Mencken: "Tertullian is credited with the motto 'Credo quia absurdum' -- 'I believe because it is impossible'. Needless to say, he began life as a lawyer."
The phrase has also been adopted as the motto for The Ancient and Honorable Order of E Clampus Vitus in modern times.
The phrase was used as an example of zen in D. T. Suzuki's book, Introduction to Zen Buddhism (which was based on essays he wrote in 1914):
"A noted Christian Father of the early Middle Ages once exclaimed: "O poor Aristotle! Thou who has discovered for the heretics the art of dialectics, the art of building up and destroying, the art of discussing all things and accomplishing nothing!" So much ado about nothing, indeed! See how philosophers of all ages contradict one another after spending all their logical acumen and analytical ingenuity on the so-called problems of science and knowledge. No wonder the same old wise man, wanting to put a stop once for all to all such profitless discussions, has boldly thrown the following bomb right into the midst of those sand-builders: "Certum est quia impossible est"; or, more logically, "Credo quia absurdum est." I believe because it is irrational; is this not an unqualified confirmation of Zen?" 
- Bühler, Pierre (2008). "Tertullian: the Teacher of the credo quia absurdum". In Stewart, Jon. Kierkegaard and the patristic and medieval traditions. Aldershot: Ashgate. pp. 131–42. ISBN 978-0-7546-6391-1.
- Götz, Ignacio L. (2002). "Tertullian's paradox". Faith, humor, and paradox. New York: Praeger. pp. 25–7. ISBN 978-0-275-97895-2.
- Sider, Robert D. (1980). "Credo Quia Absurdum?". The Classical World. 73 (7): 417–9. JSTOR 4349233. doi:10.2307/4349233.
- Garelick, Herbert (1964). "The Irrationality and Supra-rationality of Kierkegaard's Paradox". The Southern Journal of Philosophy. 2 (2): 75–86. doi:10.1111/j.2041-6962.1964.tb01469.x.
- Siemens, David F. (1964). "Conflicts between Christianity and physical science". Journal of the American Scientific Affiliation. 16: 12–5.
- Ferguson, Everett (2009). "Tertullian". The Expository Times. 120 (7): 313–21. doi:10.1177/0014524609103464.
- Bixler, J. S. (1969). "On Being Absurd!". The Massachusetts Review. 10 (2): 407–412. JSTOR 25087871.