I. What Tertullian Really Said

These words appear in the short treatise On the Flesh of Christ, in which Tertullian sought to refute those gnostic writers who denied that Christ had assumed a fully human body. It is possible to construct out of this passage something like the maxim in question, to regard Tertullian as flaunting the irrationality of Christian belief and insisting on the necessity of a faith that flies in the face of reason and evidence. Moreover, this interpretation comports with Tertullian's apparent hostility to Greek philosophy, expressed in the assertion that philosophy is the parent of heresy and the infamous and oft-quoted rhetorical question, “What has Athens to do with Jerusalem?”Footnote ² It is also significant that while the most obvious Latin term for “absurd” (absurdus) does not appear in the original, one meaning of ineptus (which I have rendered above as “unfitting”) is “absurd.” Hence, a possible translation is “it is to be believed because it is absurd.” This again could be taken as implying that absurdity is a condition for belief.

A major difficulty with this reading, as a number of Tertullian scholars have pointed out, is that it seems to be inconsistent with numerous other statements that attest to the church father's high view of rationality and advocacy of reasoned argument.Footnote ³ Thus, later in the work in which the paradox appears, Tertullian states: “But here again, I must have some reasons.”Footnote ⁴ The new Christian, he maintains elsewhere, “should believe nothing but that nothing should be rashly believed.”Footnote ⁵ In his Treatise on the Soul, Tertullian endorses Plato's elevated view of human reason, insisting that the natural rationality of the soul was impressed upon it by the God, who is himself the author of reason.Footnote ⁶ The virtues and divine origin of reason are again lauded in a short work on repentance. Once more, God is described as the “author of Reason”; everything in the world is “ordained by reason”; everything is to be “understood by reason.”Footnote ⁷ Tertullian also subscribed to a strong conception of natural law and “reason” (ratio) turns out to be one of his most frequently used nouns.Footnote ⁸ All of this seems to be at odds with the seemingly anti-rationalist sentiments of the statement certum est, quia impossibile.

The issue of the translation of ineptus, in the first part of the paradox, is more complicated. It is true that “absurd” is a possible translation of ineptus, but the context provides reasons for an alternative rendering. Vianney Décarie has argued strongly that ineptus is used here as a synonym for indignitas (unworthy, unbecoming), a term that Tertullian uses elsewhere in this passage and others that speak about the Incarnation.Footnote ⁹ It is also clear from the context that ineptus is explicitly related to stultitia (foolishness). Drawing upon 1 Corinthians 1:17–31, Tertullian rehearses the idea that while to human minds Christ's crucifixion may seem to be folly, God's “foolishness” is higher than human wisdom. So the likely connotations of ineptus, given Tertullian's preceding discussion, lie more in the direction of putative unworthiness and an ironic sense of “foolishness,” than logical absurdity. And, again, Tertullian had the Latin absurdus available to him, but chose not to use it.

Another plausible account of what Tertullian is attempting to do in this passage was put forward 100 years ago by biblical scholar James Moffatt, who directs our attention to a principle set out in Aristotle's Rhetoric. Here the philosopher addresses the question of the credibility of highly improbable events: “We may argue that people could not have believed them, if they had not been true or nearly true. And that they are more likely to be true because they are incredible.”Footnote ¹⁰ Aristotle thus proposes that the prima facie incredibility of a belief is actually a reason for accepting its likely truth, since the only thing that would make a witness believe in such an event would be that it actually happened. To put it another way, if someone wished to perpetuate a false story, they would most likely come up with something that had at least a veneer of plausibility. Whether or not we accept Aristotle's logic, the passage suggests an obvious source for Tertullian's paradoxical remarks. What Tertullian appears to be saying, then, is that the apparent unlikelihood of the events in question actually provides a rational justification for believing them. This makes Tertullian's paradox consistent with his views about the importance of reason and evidence. Added weight to this interpretation comes from the fact that Tertullian was a master of classical rhetoric and would undoubtedly have been familiar with Aristotle's key work.Footnote ¹¹

While there is a great deal more that could be said about the scholarship on this issue, it is generally safe to conclude with Tertullian scholar Eric Osborn that: “Not only did he never say ‘credo quia absurdum,’ but he never meant anything like it.”Footnote ¹² This would apply even if ineptus is translated as “absurd.” Osborn's verdict thus reinforces Décarie's insistence that “the classic formula credo quia absurdum (even when corrected to quia ineptum) does not represent the thought of Tertullian.”Footnote ¹³ Certainly there was no uptake among later Patristic writers of a principle of believing in something because it was impossible or absurd. While a number of the Latin fathers cite De carne Christi, none refers to this maxim.Footnote ¹⁴ Scholastic authors similarly drew upon Tertullian, but made no reference to his paradoxical remarks. Not until the early modern period was concerted attention directed toward this passage.

II. From Credibility to Credo

Printed editions of Tertullian's works began appearing with some frequency in the early sixteenth century. In 1521, humanist scholar Beatus Rhenanus produced a sumptuous edition of the Opera which included De carne Christi.Footnote ¹⁵ While one or two vernacular translations of single works appeared in the sixteenth century, English, French, German, and Spanish versions of single works became more common in the following century. Most often translated were the Apologeticum, Ad scapulum, De corona, and Ad martyras, with a single French translation of De carne Christi appearing in 1661.Footnote ¹⁶ Tertullian was enlisted as an ally on all sides of the confessional divides of the sixteenth century, as were most fathers of the church, and various rules and maxims were extracted from his writings.Footnote ¹⁷ Little notice, if any, was given to Tertullian's paradox until 1643, when it was cited in Thomas Browne's Religio Medici (The Religion of a Physician).Footnote ¹⁸

Browne was a physician and polymath who wrote eloquently on a wide variety of topics. His spiritual testament was a landmark of English prose and this, along with its espousal of a tolerant and open-minded Anglicanism, goes some way towards explaining its popularity throughout Europe. In 1664, William Petty reckoned it to be one of three books that was “most esteemed and generally cried up for wit in the world,” and the work's status as a religious classic was secured when in 1665 it found a place on the Index of Prohibited Books.Footnote ¹⁹ Browne structures his musings around the theological virtues faith, hope, and love, and early on in the proceedings he invokes Tertullian on the topic of faith: “Methinks there be not impossibilities enough in Religion for an active faith. . . . I can answer all the Objections of Satan and my rebellious reason with that odd resolution I learned of Tertullian, certum est quia impossibile est. I desire to exercise my faith in the difficultest point.”Footnote ²⁰

Browne's appeal to Tertullian has a two-fold significance. First, it drew the attention of a large audience to this passage in Tertullian, and from this point on the paradox came to play a role in contemporary debates about the nature of faith. Second, and equally importantly, Browne set the tone for subsequent interpretations of the paradox. Tertullian's point was that in spite of the vast improbability of Christ's death and resurrection it was, for all that, certain and to be believed. Browne, however, is more interested in the exercise of personal faith, proposing that the strength of one's faith is proportional to the improbability of its object. Whereas Tertullian says “It is certain, because it is impossible,” Browne conflates the two elements of the paradox and says something much more like “I believe, because it is impossible.” The subject of Tertullian's statement is a specific historical claim; the implicit subject of Browne's statement is his own personal faith, which could be directed to a range of objects. Much of this difference in emphasis is owing to the primary intentions of the authors and the different contexts in which they wrote. Tertullian was engaged in a controversy with the gnostic heresiarch Marcion over whether Christ had genuinely taken on a material human form; Browne sought to offer a personal account of his own religious faith. Significantly, many, if not most, subsequent references to the paradox in the early modern Anglophone context would now misquote it as credo, quia impossibile (est) (I believe, because it is impossible). This credo version of the paradox first appeared in 1659, but became increasingly common thereafter.Footnote ²¹ Browne thus not only revived Tertullian's saying, but did so in a way that left it susceptible to a significant misrepresentation. Henceforth, it would play a major role in discussions about the status of faith as an epistemic virtue or, as was increasingly the case, an epistemic vice.

The invention and subsequent proliferation of the “I believe” (credo) form of the paradox can be accounted for in a number of ways. It is a fair representation of the argument that Browne seems to be putting forward. It may be significant that, as noted earlier, Tertullian, more than any other of the church fathers, was the source of a number of Latin rules, or maxims. The credo quia impossibile est came to represent Tertullian's “rule” on the relation between faith and evidence. More generally, the post-Reformation emphasis on catechesis, which included recitation of the Apostle's Creed with its characteristic “I believe” formula, would also have likely contributed to the paradox being reformulated in this way.Footnote ²² This emphasis upon explicit statements of belief was connected with Protestant denunciations of the “papist” doctrine of “implicit faith.” This was the idea that because the vast majority of the laity were incapable of understanding and giving explicit assent to more abstruse theological doctrines, they could be held to assent to such doctrines implicitly. It was left to the Church and its councils to decide the propositional content of doctrines, and the laity were enjoined simply to trust that the Catholic magisterium had got the doctrines correct. Protestant reformers took a particularly harsh view of this principle, insisting that all the faithful have a full knowledge of what they were supposed to believe in.Footnote ²³ Recitation of creedal statements, often in the “I believe” form, was thus recommended to the laity so that they could give explicit assent to the doctrines of their religion. For this reason, condemnations of the principle “I believe, because it is impossible” were frequently articulated in the context of criticisms of the implicit faith. “You confirm the old Sentence, Credo quia impossibile est,” wrote William Freke, “Do you think to make your Doctrine prevail by these means, by a dead anathematizing implicite Faith, fitter for Paganism than Christianity.”Footnote ²⁴ The perpetuation of the paradox in its new credo form can thus be understood in light of its role in contemporary religious controversy.

Most of Browne's contemporaries took a dim view of his credo, and the view of faith that it seemed to entail.Footnote ²⁵ Among more prominent figures to comment adversely on the supposedly over-credulous faith of Browne and Tertullian were Henry More, John Norris, Edward Stillingfleet, Jeremy Taylor, Robert Boyle, and John Locke. It is significant that, without exception, all misquoted the saying as Credo quia impossibile—I believe because it is impossible. Cambridge Platonist Henry More thus censured “that witty Father of the Church” for not adducing reasons for belief and, in a clear reference to Thomas Browne, insisted that there were no impossibilities in the Christian religion. Anglican Divine Edward Stillingfleet, who shared More's latitudinarian views and advocacy of reasonable religion, described Tertullian's supposed words as “very harsh,” arguing that Christian faith is entirely reasonable. Jeremy Taylor spoke of “the folly” of Tertullian's maxim, while John Norris dismissed it as a “religious flourish.” Robert Boyle rejected the principle, remarking that we ought only assent to a proposition revealed by God “as far as we understand it.” John Locke offered his verdict in the section of his Essay concerning Human Understanding devoted to a discussion of faith and reason: “Credo, quia impossibile est: I believe, because it is impossible, might, in a good Man, pass for a Sally of Zeal; but would prove a very ill Rule for Men to chuse their Opinions, or Religion by.”Footnote ²⁶

These writers were Protestants, and a number of them were keen to identify and condemn a form of uncritical and unwarranted faith that they associated with Catholicism. Implicit faith was the general form of the over-credulous faith, but it took specific forms too. Uncritical acceptance of the scholastic doctrine of transubstantiation was the prime contemporary instance. This doctrine involved an Aristotelian account of how, during the Eucharist, the elements of bread and wine literally become the body and blood of Christ. Many Protestants argued that the Catholic commitment to the doctrine of transubstantiation was a paradigm case of belief in impossibilities or absurdities: “Of all the Doctrines that ever were in any Religion, this of Transubstantiation is certainly the most abominably absurd,” wrote Anglican Archbishop John Tillotson in a typical assessment.Footnote ²⁷ Thus, condemnation of Tertullian's credo and of transubstantiation routinely appear together, along with the implication that Tertullian's position gave license to believe in impossible things. “In favour of this monstrous tenet,” complained Thomas Smith, “the Romanists object to us the incomprehensibility of the mysteries of faith; and hence think, that they may elude all those unanswerable difficulties, which this new doctrine is charged with, and that there is argument enough to satisfie their doubts in that misapplyed saying, the effect, it may be, of rapture and indiscreet devotion, Ideo credo, quia est impossibile.”Footnote ²⁸ Transubstantiation, accordingly, became the most notorious instance of a religious credulity that was predominantly a Catholic affliction.

Catholicism was not the only concern, however. If papists were prone to believing only what they were told, “enthusiasts” went to the opposite extreme of believing what they pleased.Footnote ²⁹ In both cases, belief in impossibilities was the end result. The credo, then, was deployed against both Catholics and enthusiasts. We are not “so far elevated with Enthusiasme, as to think all incomprehensible infallible and conclude with that credulous Father Certum est quia impossibile,” wrote White Kennett in 1681.Footnote ³⁰ Significantly, John Locke's introduction of the paradox in his Essay is immediately followed by the chapter “Of Enthusiasm.” The “pious rant of a mad enthusiast,” was Soame Jenyns's colorful characterization of the credo—a description that was frequently repeated in a number of eighteenth- and nineteenth-century sources.Footnote ³¹ For the historically informed, the connection between credo quia impossibile and enthusiasm gained added weight from the fact that in later life Tertullian adopted Montanism, a charismatic sect (later a heresy) that embraced ecstatic visions and private revelations.

All of this related to a more general early modern discussion about the nature of faith and belief, and their relation to reason and evidence. The so-called “epistemic turn” of early modern philosophy is relevant in this context. In his Meditations (1641), Descartes had gone through the exercise of doubting all of his knowledge before arriving at the general principle that if we are to avoid error, we must withhold assent from ideas that are not clear and distinct.Footnote ³² Descartes was careful to make exemptions for particular morals and matters of faith. These exceptions were made on prudential grounds to do with the conduct of life.Footnote ³³ Yet this focus on the justification of beliefs sees faith gradually moved out of the sphere of the theological virtues and into a neutral epistemic and evidentialist framework. Works offering “evidences of the Christian religion” and its various forms thus abound in the latter half of the seventeenth century.Footnote ³⁴ Such justificatory procedures seemed all the more necessary in light of the competing confessional systems of post-Reformation Europe.

In the Anglophone world this relocation of faith into the epistemic sphere was also evidenced by a shift of emphasis away from the idea of faith as balanced between trust (fiducia) and assent (assensio, assensus), toward something exclusively concerned with the latter. Thomas Hobbes, for example, puzzled over the meaning of the creedal formulation “believe in,” wondering how it could differ from “believe that.” In the end, he maintained, belief cannot be about “trust in the Person,” but is rather “Confession and acknowledgement of the Doctrine.”Footnote ³⁵ To believe in God, then, is not to put one's trust in God, but is to give intellectual assent to the proposition “God exists.” A number of seventeenth-century thinkers came to argue that such assent must be made on the basis of evidence. Edward Stillingfleet defined faith as “an assent upon evidence.” Unless the believer has reasons for the mind's assent, without which “faith would be an unaccountable thing, and . . . exposed to the contempt of all unbelievers.”Footnote ³⁶ John Locke is similarly committed to a version of evidentialism. “Faith,” he maintains, “is nothing but a firm assent of the mind: which . . . cannot be afforded to any thing, but upon good Reason: and so cannot be opposite to it.”Footnote ³⁷ The person that believes without reason for believing, concludes Locke, “may be in love with his own Fancies, but neither seeks truth as he ought, nor pays the Obedience due to his Maker.” Locke insists that it is our duty, as reasonable beings, not to assent to things that are against reason.Footnote ³⁸ Such a commitment to what philosophers now refer to as the “ethics of belief” suggests that there is something morally improper about believing things in the absence of compelling evidence. Believing something because it was impossible was thus directly contrary to a Lockean conception of properly grounded faith.

In sum, Thomas Browne introduced Tertullian's paradox to an early modern audience and did so in a way that facilitated the invention of the credo form. While this form had a tenuous connection with Tertullian, it served a number of contemporary purposes relating to discussions about the nature of faith and evidence on the one hand, and about the believing subject on the other. Crucially, it was no longer anchored to the specific doctrine that Tertullian had been concerned with in De carne Christi and could thus play a role in anti-Catholic polemic, criticism of implicit faith, and attacks on transubstantiation. By the mid-eighteenth century, credo quia impossibile had entered common discourse as a by-word for a form of religious irrationality. It was “a noted saying” or, more pejoratively, “a celebrated rant.”Footnote ³⁹ It could be, and eventually was, applied more broadly to the doctrine of the Trinity.Footnote ⁴⁰ This broader deployment, from a context of confessional disputation to a general critique of Christianity itself, was characteristic of uses of the credo in eighteenth-century France.

III. The French Connection: From Impossible to Absurd

If Thomas Browne introduced the paradox to Anglophone readers, the erudite Huguenot author Pierre Bayle (1647–1706) and Enlightenment philosophe Voltaire (1694–1778) performed this service for French readers. Tertullian's paradox did not enjoy any significant profile in French literature until it was reproduced in Bayle's classic Dictionnaire historique et critique.Footnote ⁴¹ This work is an eccentric encyclopedia that catalogued philosophical and religious controversies, and historical events and persons, with a good measure of indelicate relations of various kinds, all displaying a remarkable level of textual skill and philosophical acumen. It appeared in a number of successively revised editions from 1696 and exercised a major influence on Enlightenment philosophes. One of its central messages is that philosophy and reason are unreliable guides to truth. On the specific question of the relation between faith and reason, Bayle's suggestion on the surface of things seems to be that, given the fallibility of reason, we must have recourse to revelation and faith. Some readers regarded this as subterfuge and a mask for infidelity, judging the Dictionnaire to be a thinly veiled endorsement of atheism. Whether this assessment is accurate has been a matter of discussion ever since, but there is little doubt that Bayle's elliptical writings provided ammunition for subsequent Enlightenment critiques of Catholicism and religion more generally. Bayle rejected accusations of infidelity, responding to critics in “clarifications” appended to later editions of this work (from 1702 onwards) where he explicitly defended a form of fideism. The highest form of faith, he insisted, is that which “embraces those truths most opposed to reason.”Footnote ⁴² This is an unmistakable echo of Thomas Browne and, indeed, Browne was enlisted in support of Bayle's stance. It was on this occasion that Bayle also repeated the second part of the maxim, mentioning its author by name and citing it in both French and Latin: Cela est certain, parce que cela est impossible—Certum est quia impossibile.Footnote ⁴³

Bayle's forthright fideism, and his marshaling of an impressive range of patristic resources to support it, generated significant misgivings among those convinced that faith and reason were compatible, and who were accordingly concerned that Bayle's position was susceptible to appropriation by religious sceptics. Growing literacy rates and book ownership in France in the late seventeenth and early eighteenth centuries further fueled anxieties amongst the orthodox that unsophisticated readers might be easily seduced by superficial and simplistic readings of complex theological formulations.Footnote ⁴⁴ Given this, it was not surprising that Bayle's work elicited a number of robust responses specifically devoted to the relation of faith and reason.Footnote ⁴⁵ Most notable was a major section of Gottfried Wilhelm Leibniz's Théodicée (1710) that addressed the theme of “The Conformity of Faith with Reason.” In this classic work, Leibniz could now speak of “the famous passage of Tertullian,” giving an indication of just how influential the efforts of Browne and Bayle had been in raising the profile of the maxim. As might be expected, Leibniz cautioned against reading Tertullian's paradox as an advocacy of extreme fideism or irrationalism. Reproducing the original Latin, but offering no translation, he insisted that this was a “sally” that “can only be meant to concern the appearance of absurdity.”Footnote ⁴⁶

In the end, these attempts by Leibniz and others to mitigate the severity of Tertullian's words, as mediated by Bayle, were only partially successful. The fears of more moderate commentators were fully realized when Voltaire forged his own distinctive version of the paradox, establishing for it a permanent place in the armory of anti-clerical polemics and critiques of the Christian revelation. In English hands, “It is certain because it is impossible,” had become “I believe because it is impossible.” Voltaire introduced his own modification to the “I believe” version of the paradox, grafting onto it the condition from the first half of the expression by replacing impossibile with ineptus. For good measure he translated ineptus with the unambiguous and uncompromising absurde—“I believe because it is absurd”—and ascribed the maxim to a figure much more central to the Christian tradition—St. Augustine.

Voltaire's philosophical dictionary (Dictionnaire philosophique, 1764–1778) and his Questions on the Encyclopedia (Questions sur l'Encyclopédie, 1770), were modeled on Bayle's original, and these works preserve some of the potentially subversive elements of the prototype. A key stage in the further evolution of the maxim begins with the article “Faith” (Foi) in the Dictionnaire. Voltaire introduces the article with a characteristically droll relation of an exchange between Pope Alexander VI and the philosopher Pico della Mirandola concerning the paternity of one of a number of children widely thought to have been begotten by the Holy Father himself. When questioned by the Pope, Pico prudently attributes paternity to the child's legitimate father, whose impotence was as much a matter of common knowledge as was the papal propensity for philandering. Pressed further by the Pope, Pico disarmingly declares that he believes this “by faith,” where faith is understood as “believing things because they are impossible.”Footnote ⁴⁷ Alexander agrees that this is a worthy principle.

In the anonymously published Le Dîner du comte de Boulainvilliers (1767), Voltaire takes the step of introducing absurdity into the formula. At an imaginary meal, three interlocutors—de Boulainvilliers, the pious Abbé Couet, and the freethinker Nicolas Fréret—discuss whether philosophy is more useful to the human race than religion. In full retreat, the Abbé observes that Augustine had defended the principle: “I believe because it is absurd, I believe because it is impossible.”Footnote ⁴⁸ Fréret eventually bests the Abbé through the weight of his scholarship, and the defender of Christianity grudgingly concedes that he secretly sympathizes with his adversaries. The attribution to Augustine is repeated in Voltaire's article “Economy of Speech” in the Questions sur l'Encyclopédie.Footnote ⁴⁹ Here Voltaire notes that “speaking with economy” (being economical with the truth, as we would say in English) was characteristic of the fathers of the church and of theology generally: “St. Augustine speaks with economy when he says, I believe because it is absurd. I believe because it is impossible. These words, which would be extravagant in mundane matters, are very respectable in theology. They signify that what is absurd and impossible to the eyes of mortals is not so to the eyes of God.”Footnote ⁵⁰ This is the first time that “I believe” is conjoined with “because it is absurd.” Thereafter, this would become the standard formulation, even when the misattributed authorship was corrected. Voltaire's seminal Dictionary entries (and to a lesser extent Le Dîner) thus became the urtexts for a version of the paradox that included two elements: the “because it is absurd” construction and the attribution to Augustine. Both serve as important markers for tracing the subsequent influence of Voltaire's reworking of the paradox.

The most obvious source for the “I believe” component of Voltaire's version of the formula is Locke's Essay, which appeared in 1700 in a French translation by Pierre Coste.Footnote ⁵¹ Neither Locke's original, nor the French translation, mentions Tertullian, and both the English and French versions provide the Credo quia version of the paradox.Footnote ⁵² So it is highly likely that Voltaire, a great admirer of Locke, encountered the unattributed paradox in the Essay. Significantly, in his remarks on Locke in the Lettres philosophiques, Voltaire seized upon Locke's speculations about thinking matter to argue—contrary to Locke's own views—for the opposition between faith and reason, and for the tension between the “mysteries” of religion and the “demonstrations” of philosophy.Footnote ⁵³

However, Locke refers only to the second part of the paradox (as does Bayle). If Voltaire's absurde is a translation of ineptus, rather than just a variation on “impossible,” he would need to have encountered the full version of the maxim. Here the obvious source is Leibniz whom, given the subject matter of Candide, Voltaire must surely have read. In that case, Voltaire would have chosen absurde to render Tertullian's ineptus. As noted earlier, setting aside questions of context and Tertullian's original intention, this would be a legitimate translation.Footnote ⁵⁴ However, it is given to misunderstanding, particularly when conjoined with “I believe.” Perhaps for this reason, up until this point, no English version of the paradox had spoken of “absurdity.” The French edition of De carne Christi of 1661 and the subsequent translations of 1841 and 1844 avoid absurde.Footnote ⁵⁵ Voltaire's contribution, then, is a somewhat provocative translation of ineptus (if it is indeed a translation) and his conjoining it with the existing English credo version of the paradox.

This still leaves the puzzle of Augustine's putative authorship. Both Bayle and Leibniz are clear in their attribution of the saying to Tertullian, as are most other authors who reference the paradox. It follows that Voltaire's misattribution was either careless or calculated. If it was a mistake, it was a fortuitous one. Augustine had a considerably greater literary output than Tertullian, making the negative claim that he had not said something more difficult to sustain. Crucially, though, Augustine was central to the Christian tradition in a way that Tertullian was not. Late in life, Tertullian had defected from the Catholic Church to embrace the heterodox sect of Montanism. That a particular statement of Tertullian's might exemplify the whole of the Christian tradition was thus susceptible to criticism. This could hardly be the case with Augustine, whose authority was invoked by all Christian confessions. Given that Voltaire's concern was to critique the Christian religion in general, unlike his English counterparts who sought only to critique some version of it, Augustine served his purposes in a way that Tertullian could not. (In fact, the only theological writer whose authority could rival that of Augustine was Thomas Aquinas, and somewhat predictably, at least one French source later attributed the paradox to him.)Footnote ⁵⁶ Added to this, Voltaire had come to regard contemporary manifestations of Augustinian thought, and Jansenism in particular, as exemplary instances of religious irrationality. And he regarded Augustine himself as the embodiment of paradox: “an African debauchee and penitent, Manichæan and Christian, tolerant and persecuting—who passed his life in perpetual self-contradiction.”Footnote ⁵⁷ Whether deliberate or not, then, Voltaire's linking of the paradox to Augustine was consistent with his polemical intentions. A number of authors in the eighteenth and nineteenth centuries were to follow him in fathering the saying upon Augustine, and the frequency of this misattribution serves as a measure of the extent of Voltaire's influence.Footnote ⁵⁸ In time, Tertullian came to be identified as the true source of the paradox, and most modern rehearsals of the paradox get this right. But Voltaire's enduring contribution was to link absurdity to religious belief—I believe because it is absurd—and the expression that embodies this connection has persisted to the present.

Voltaire's Dictionnaire went through a number of editions and translations, and its alphabetically arranged articles in later editions drew freely upon the material in the Questions sur l'Encyclopédie. Voltaire had been particularly concerned to ensure the Dictionnaire’s accessibility, and its inexpensive “portatif” (portable) format meant that it reached a wide audience. Not surprisingly, his ironic remarks on the general absurdity of many religious beliefs, now underwritten by the authority of Augustine, were widely repeated. To consider just a few examples, the “I believe because it is absurd / I believe because it is impossible” combination is recycled in J. B. Salgues's anthology, Mélanges inédits de littérature de J. B. de La Harpe (1810), in which Augustine's dual declarations are derisively said to capture the essence of “our holy religion.”Footnote ⁵⁹ In 1831, literary critic Gustave Planche further elaborated Voltaire's original construction, characterizing the “Augustinian” position thus: “I believe because it is absurd; I believe because I do not understand; I believe because I do not know; because others have taken it upon themselves to know and understand for me.”Footnote ⁶⁰ Joseph Décembre and Edmond Alonnier inform readers of the article ‘Dogme’ in their Dictionnaire populaire (1861) that “theologians say we must see with the eyes of faith,” and repeat with Augustine, “I believe because it is absurd.”Footnote ⁶¹ The saying also transcended specifically religious contexts, with a reference in Auguste Blanc's Histoire des conspirations et des exécutions politiques (1846), suggesting that the phrase was becoming a commonplace way of labeling the irrational and unjustified beliefs of the vulgar.Footnote ⁶² The corrupted maxim also appeared in the pages of the newspapers such as Le Siècle, Courrier de Paris, Le Monde illustré, and Morning-Chronicle.Footnote ⁶³

As was the case in seventeenth-century England, not all rehearsals of the paradox were totally disapproving. Jacques-Charles Bailleul observed in his Dictionnaire critique (1842) that the eighteenth century had been much amused by the passage in Augustine that affirmed belief in the absurd. Bailleul sought to soften the harshness of the affirmation by proposing that the Latin absurdus did not equate to the French absurde, and that the saying was really about the incomprehensibility of God.Footnote ⁶⁴ This, of course, missed the point that absurdus was not in the Latin original at all. A number of vigilant scholars also picked up on the misattribution. In the Dictionnaire des sciences philosophiques (1845) compiled by Jewish philosopher Adolphe Franck, the article “Foi” records the maxim as “Credo quia absurdum,” but now attributes it to Tertullian.Footnote ⁶⁵ Indeed, a number of French sources in the second half of the eighteenth century provide the correct authorship, although they retain the modified formula.Footnote ⁶⁶ Only a few commentators were alert to both the incorrect attribution and the corruption of the original. Gaston de Flotte made something of a habit of picking up on the misattributed misquote, listing several occurrences in the Parisian daily Le Siècle, the Courrier de Paris, and the popular Le Monde illustré during the 1860s. He duly noted the true author and provided the Latin original, observing that Voltaire had clearly not read, or had not read closely enough, Augustine and Tertullian, whom he nonetheless “cited so often.”Footnote ⁶⁷

In spite of these observations, “I believe because it is absurd” was just too good a formula to succumb to the textual evidence. Voltaire's version came to be repeated in English, German, and Italian sources.Footnote ⁶⁸ Its retranslation back into Latin lent it a veneer of legitimacy. And no doubt the principle quidquid latine dictum sit altum videtur—anything said in Latin sounds profound—also helped sustain the fiction of its ancient provenance. Its inclusion in reference works further consolidated its status in the literary and intellectual world. To take a single example, Wilhelm Krug's Allgemeines Handwörterbuch der philosophischen Wissenschaften (General Dictionary of the Philosophical Sciences, 1827–1828), was a five-volume dictionary with entries on philosophical words and expressions arranged alphabetically. Its second volume has a separate entry for “Credo, quia absurdum est,” where it is described “as a most absurd maxim, in spite of the philosophical reputation that precedes the vaunted Father of the Church (Augustine).”Footnote ⁶⁹

The entry in works such as Krug's Handwörterbuch signals a further stage in the evolution of the paradox. The dictionary of Voltaire had an overt ideological purpose, as did the Encyclopédie. Nineteenth-century dictionaries and handbooks, however, aspired to objectivity and comprehensibility. They were more obviously reference works in the modern sense. The appearance of the credo in this literature acted as a guarantor of its patristic pedigree. Thereafter it would appear in numerous reference works with its own dedicated entry, confirming Tertullian's advocacy of belief in absurdities and not infrequently suggesting this as a common stance in theology.Footnote ⁷⁰ This remains true for recent handbooks and philosophical dictionaries. Again, to consider just one of numerous examples, Simon Blackburn's Oxford Dictionary of Philosophy offers this under the heading “credo quia absurdum est”: “Also known as Tertullian's dictum or paradox. Literally, I believe because it is absurd: that is, the very impossibility of a proposition becomes (mostly in theology) a kind of motivation for belief in it.”Footnote ⁷¹

In Voltaire's hands, then, the paradox took on a form that lent itself to easy repetition, becoming a convenient shorthand for the absurdity of all religious faith. Voltaire's status as one of the Enlightenment's most witty and articulate critics of traditional religion ensured that the maxim, in its new form, reached a wide audience. Its regular appearance in reference works lent it an air of authenticity and provided a platform for its continued use into the twenty-first century. Largely owing to the influence of Voltaire, the paradox was destined to become an enduring element of a common narrative about the gradual emergence of secular rationality in the modern West.

IV. Tertullian's Credo in Late Modernity

Over the course of the last century, generally speaking, the paradox has been deployed in two main ways, both of which reflect its Enlightenment origins. First, the maxim “I believe because it is absurd” has come to stand in for Christianity or religion in general, as contrasted with science, philosophy, or some broad notion of Enlightenment rationality. In the wake of the stadial histories of the eighteenth and nineteenth centuries (in which history is imagined to move through progressive stages), the credo could represent a particular phase of history—typically, an “age of faith.” With the growth of the social sciences it also was thought to represent a particular mindset or cognitive state—again one that could be accounted for psychologically and assigned to a primitive stage of human development.

A second, and more discriminate, use of the paradox has it representing a particular type of religiosity—a type that is usually contrasted unfavorably with more rational forms of religious belief. This more restricted application has been used to account for different approaches to reason within the Christian tradition or, drawing on the social sciences, to describe different religious “types” or mindsets. Again, though, this is equally a product of an Enlightenment understanding of religion, typified in Locke's idea that we have an obligation to ensure that all our beliefs are grounded in evidence.

Sigmund Freud provides an instructive example of the first of these themes. Freud used the paradox to bolster his notion of religion as infantile wish fulfillment, characterized by beliefs that invariably seek exemption from the scrutiny of reason.Footnote ⁷² In doing so, he set up the possibilities for offering a general psychological account of the origins of religious belief, along with an explanation for how a particular mentality might characterize a historical era: “Credo qua [sic] absurdum est . . . became the motto of the [patristic] age,” we are informed by one history of psychology.Footnote ⁷³ Another tells us that Tertullian “set the stage for the Middle Ages by emphasizing the futility of reason. . . . His position would frustrate later efforts to elevate the role of reason in philosophy and science.” For good measure, responsibility for witch hunts and misogyny was added to the list of Tertullian's achievements: “Tertullian stands at the headwaters of a virulent and often deadly misogynist movement that persisted through the Middle Ages and Renaissance, reaching its pinnacle in European witch hunts from 1500 to 1700.”Footnote ⁷⁴ Some histories of philosophy, general histories of Western thought, and even some histories of science, will make a similar point, reinforced by entries in philosophy handbooks and dictionaries that confer historical veracity on the maxim.Footnote ⁷⁵ This referencing of the past is often intended to make a point about the present, on the assumption that unwanted vestiges of religious irrationality have persisted into the late modern period. German philosopher Ernst Cassirer thus suggested that the “same fundamental psychological forces which prevailed at the origin of religion also determine its further progress and continue to influence its development.” The motto “I believe because it is absurd,” Cassirer maintained, “exhibits its old force here and everywhere.”Footnote ⁷⁶ Tertullian's credo thus came to stand in for a generic religious “type,” the mood of a historical era, and a persistent contemporary source of irrationality.

An obvious site for the deployment of the credo is the narrative of a supposed conflict between science and religion. This narrative got underway in the late nineteenth century and has stubbornly resisted the demythologizing efforts of historians of science.Footnote ⁷⁷ One of the progenitors of the conflict thesis, John William Draper, observes in his seminal History of the Conflict between Religion and Science (1874) that Tertullian's negative attitude towards science “affected the intellectual development of all Europe.”Footnote ⁷⁸ Andrew Dickson White, the other key nineteenth-century advocate of historical conflict, makes reference to the paradox, albeit in passing, as do Charles Darwin and Thomas Henry Huxley.Footnote ⁷⁹ Subsequently, Max Weber, in his famous lecture “Science as a Vocation,” proposed that the credo exemplifies the necessary opposition between science and religion. Contriving yet another Latin variant—Credo non quod, sed quia absurdum (I believe nothing except that which is absurd), which he attributes to Augustine—Weber claims that this principle signifies “the tension between the value spheres of ‘science’ and religious salvation cannot be overcome.”Footnote ⁸⁰ Not surprisingly, Tertullian's paradox is a staple of popular twenty-first-century writings that assert the intrinsic incompatibility of science and religion.Footnote ⁸¹

There are more subtle uses of the paradox. If Freud used Tertullian to characterize the irrationality of religion in general, Carl Jung, in his Psychological Types, sought to make him a particular type of religious sensibility, and one that contrasted with a another religious type more favorably disposed to rapprochement between religion and reason. Thus, Tertullian's credo exemplified the “sacrifice of the intellect” (a concept also found in Weber), while the Alexandrian church father, Origen, who is regarded as upholding the dignity of reason, exemplified what Jung referred to as the sacrificium phalli.Footnote ⁸² (Origen was reputed to have taken an overly literal view of a biblical reference which refers to becoming a eunuch for the Kingdom of God [Matthew 19:12].) Rather than standing in for religion in general, Tertullian could thus serve as the model for a more specific kind of religiosity. Jung's distinction survives in a common dichotomy between a more rational, philosophy-friendly, Greek-speaking East, and more fideistic, philosophy-hostile, Latin-speaking West.

Tertullian's paradox continues to function within theological discussions. In Reason and Revelation in the Middle Ages (1939), French historian of medieval philosophy Etienne Gilson identifies Tertullian as the chief exemplar of an anti-rationalist tradition that he designates “the Tertullian family.” Had the Middle Ages produced only members of Tertullian's “family,” Gilson declared, this period could justifiably be called the “Dark Ages.” Fortunately there was “another spiritual family, much more enlightened than the first one, and whose untiring efforts to blend religious faith with rational speculations have achieved really important results.”Footnote ⁸³ Augustine and Anselm, with their respective formulae nisi credideritus, non intelligetis (unless you believe, you will not understand) and fides quaerens intellectum (faith seeking understanding), represent this enlightened tradition.Footnote ⁸⁴ Another distinguished medievalist, Norman Kretzmann, concurs, similarly contrasting Tertullian with Augustine and Aquinas, to whom he is more favorably disposed. Tertullian, he declares, “viewed the application of reasoning to religious truth as denigrating or at best a waste of time.” Once Augustine got his project for “philosophical theology” off the ground, “Tertullian's party was put out of power for a thousand years.”Footnote ⁸⁵ For both Gilson and Kretzmann, Tertullian is a foil, intended to highlight the inherent reasonableness of the historical figures with whom they tacitly sympathize. In Kretzmann's case, moreover, Tertullian is also a stalking horse for the “reformed epistemology” associated with such thinkers as Alvin Plantinga and Nicholas Wolterstorff, according to whom belief in God is rational, even if it is not supported by evidence.Footnote ⁸⁶

The twentieth and twenty-first centuries thus witnessed an interesting convergence between the characterizations of Tertullian on the part of those generally hostile to religion and largely innocent of the history of Christianity, and groups of scholars who are more sympathetic to Christianity and better informed about its history. This convergence of interests, from parties that would otherwise be opposed to each other, serves to make the credo doubly secure, and likely to have a long future.