Credo Quia Absurdum
Credo quia absurdum is a Latin phrase that means "I believe because it is absurd."
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 is often incorrectly used as an example of the irrationality of religious faith. But in the larger context of Tertullian's overall argument, which is that highly improbable stories are actually unlikely to be fabrications, he is clearly not advocating an irrational approach to faith.
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It has also been quoted, not as a basis of, but in relation to, Zen