‘I BELIEVE BECAUSE IT IS ABSURD’: THE ENLIGHTENMENT INVENTION OF TERTULLIAN’S CREDO Peter Harrison Institute for Advanced Studies in the Humanities, University of Queensland Preprint. Final copyedited version in Church History 86 (2017, 339-64. ABSTRACT: Tertullian is widely regarded as having originated the expression Credo quia absurdum (est) (I believe because it is absurd) and the phrase often appears in contemporary polemics about the rationality of religious belief. Patristic scholars have long pointed out that Tertullian never said this or meant anything like it. However, little scholarly attention has been paid to the circumstances in which this specific phrase came into existence and why, in spite of its dubious provenance, it continues to be regarded by many as a legitimate characterization of religious faith. This paper shows how Tertullian's original expression—“It is certain, because impossible”—was first misrepresented and modified in the early modern period. In seventeenth century England a “credo” version—I believe because it is impossible— became the common form of Tertullian's maxim. A further modification, building on the first, was effected by the Enlightenment philosophe Voltaire, who added the “absurdity condition” and gave us the modern version of the paradox: I believe because it is absurd. These modifications played a significant role in Enlightenment representations of religion as irrational, and signal the beginning of a new understanding of faith as an epistemic vice. This doubtful maxim continues to play a role in debates about the cognitive status of religious faith, and its failure to succumb to the historical evidence against it is owing to its ongoing rhetorical usefulness in such debates The North African Church Father Tertullian (c.160-c.225) has the misfortune to be best remembered for something he never said: Credo quia absurdum (est)—I believe because it is absurd. This maxim makes a routine appearance in a wide variety of contemporary contexts: philosophical assessments of the rationality of religious belief, accounts of the putative conflict between science and religion, dictionaries and handbooks, histories of Western thought, and discussions of different theological approaches to knowledge. Almost invariably, Tertullian is depicted as the personification of a regrettable religious anti-rationalism. Patristic scholars have long pointed out that Tertullian said something rather different to the saying typically credited to him. He did not think that the absurdity of a proposition provided a justification for believing it, and almost certainly thought that faith should be supported by reason. Yet the maxim ‘I believe because it is absurd’ continues to have a life as the one thing that well-read people know about this early Christian writer. This paper is not primarily an attempt to set the record straight, although it will briefly consider the original context of Tertullian’s paradox and what he meant by it. Its main purpose is to establish when the expression came to be changed from its original form