Credo quia absurdum is a Latin phrase that means "I believe because it is absurd", originally misattributed to Tertullian in his De Carne Christi. It is believed to be a paraphrasing of Tertullian's "prorsus credibile est, quia ineptum est" which means "it is completely credible because it is unsuitable", or "certum est, quia impossibile" which means "it is certain because it is impossible". These are consistent with the anti-Marcionite context. 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 to a personally religious context.
History of the phrase
Origins
The original phrase, before being transmuted through Enlightenment rhetoric to its modern form "I believe because it is absurd", appeared in Tertullian's work De Carne Christi (), read by scholars as "I believe because it is unfitting". The context is a defense of the tenets of orthodox Christianity against docetism:
The consensus of Tertullian scholars is that the reading "I believe because it is absurd" sharply diverges from Tertullian's own thoughts, given the priority placed on reasoned argument and rationality in his writings. In the same work, Tertullian later writes "But here again, I must have some reasons." Elsewhere, he writes that the new Christian “should believe nothing but that nothing should be rashly believed.” Scholars note further examples of where Tertullian acts by following a method of reasoned argument. The meaning of the phrase may relate to 1 Corinthians 1:17–31, where something foolish to a human may be a part of God's wisdom, or Tertullian may be repeating an idea rehearsed in Aristotle's Rhetoric, where Aristotle argues that something is more credibly true if it is an incredible claim, on the reason that it would not have been made up if it were truly so incredible to the human mind. Eric Osborn concludes that “the classic formula credo quia absurdum (even when corrected to quia ineptum) does not represent the thought of Tertullian."
Transmission into the early modern era and modern use
No notice was given to this maxim throughout the classical and medieval periods, however, the maxim first began to receive attention and then undergo change during the early modern era. In 1521, the humanist scholar Beatus Rhenanus produced an edition of Tertullian's De carne Christi. The only French translation of this work to appear in the 17th century was Louis Giry's 1661 edition. 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), 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." Many of Browne's contemporaries criticized him and Tertullian for this maxim, including Henry More, Edward Stillingfleet, Robert Boyle, and John Locke. As Protestant anti-Catholic polemic and rhetoric grew, many writers began associating certain Catholic doctrines (and later broadly to Christianity itself by some other writers), especially transubstantiation, with this maxim. 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. Then Voltaire, in his anonymously published Le Dîner du comte de Boulainvillier (1767), took the maxim to the next step and shifted the phrase from "I believe because it is impossible" to "I believe because it is absurd". Voltaire also attributed it to Augustine instead of Tertullian, a much more central figure in Christian history. 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, 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.