A concise theological compendium from a leading North African bishop defending Nicene Trinitarianism, Chalcedonian Christology, and Augustinian soteriology against heretical movements of the early 6th century, while presenting a systematic "rule of faith" for orthodox Christians living under Arian Vandal rule.

St. Fulgentius of Ruspe depicted as a bishop with a book (17th-century painting)
St. Fulgentius of Ruspe depicted as a bishop with a book (17th-century painting). Fulgentius's treatise De Fide reflects his role as a guardian of orthodox doctrine in an age of theological controversy.

St. Fulgentius of Ruspe depicted as a bishop with a book (17th-century painting). Fulgentius’s treatise De Fide reflects his role as a guardian of orthodox doctrine in an age of theological controversy.

St. Fulgentius of Ruspe (c.467–533) was a North African bishop and a staunch defender of Nicene and Augustinian theology in the late 5th and early 6th centuries according to Britannica. De Fide (also known as De Fide ad Petrum or De regula fidei) is a one-book compendium of Catholic doctrine addressing various heresies as Encyclopedia.com notes. It was written as a response to a request for clear guidance on the faith – according to one account, a layman named Donatus asked Fulgentius to help refute Arian arguments – prompting this succinct exposition of “the Orthodox Faith and the diverse errors of the heretics” according to CCEL. In what follows, we examine the treatise’s major theological themes (Christology, soteriology, and Trinitarian doctrine), situate it in its historical context amid ongoing controversies like Arianism and Semi-Pelagianism, analyze its structure and rhetoric, and consider its influence and textual history.

Major Theological Themes in De Fide

Trinitarian Doctrine

De Fide opens by affirming the fundamental tenet of Trinitarian orthodoxy: the unity of God in three distinct, co-equal persons (Father, Son, and Holy Spirit). Fulgentius insists on one Godhead shared by the Trinity – “The Holy Trinity is one God, the Father and the Son and the Holy Spirit. There is one nature of the three…” (as he writes in the treatise) – in direct opposition to both Sabellian and Arian errors as described in CCEL. Sabellian (Modalist) heresy, which blurred the persons, is rejected by stressing real distinctions between Father, Son, and Spirit, while Arianism, which subordinated the Son and denied His co-equal divinity, is countered by insisting the Son is of one substance with the Father according to CCEL. Fulgentius explicitly refutes the Arian reading of John 1:1, which tried to use the phrase “the Word was with God” (apud Deum) to imply the Son is separate or inferior – he ingeniously turns their argument on its head to uphold consubstantial unity as noted by CCEL. He also condemns the Macedonian heresy (which denied the divinity of the Holy Spirit) and strongly upholds that the Spirit, too, is true God equal to Father and Son per CCEL. Throughout De Fide Fulgentius employs the language of the Nicene Creed, emphasizing one divine nature and co-eternal triunity, thereby defending the orthodox doctrine of the Trinity against all forms of deviation.

Christology

A substantial portion of De Fide is devoted to Christology – the doctrine of Christ’s person and natures – reflecting the post-Chalcedonian context. Fulgentius articulates a clearly Chalcedonian position: Christ is one person in two natures, divine and human, without confusion or division according to CCEL. He explicitly names and rejects opposing Christological heresies. On one hand, he condemns Nestorianism, which divided Christ into two persons, affirming that the Church “repudiates the two persons” in Christ as noted in CCEL. On the other hand, he rejects Eutychian/Monophysite error, “asserting the two natures” of Christ against any who would collapse them into one as CCEL explains. Fulgentius also targets Photinian doctrine (stemming from Photinus of Sirmium), which held Christ was a mere man who did not pre-exist – this heresy is refuted by emphasizing Christ’s true divinity and eternal generation from the Father per CCEL. In positive terms, Fulgentius stresses that the incarnation is real: the Word truly assumed a complete human nature (body and rational soul) in the unity of the Person. He writes that “the eternal Divine Nature could not be conceived and born of human nature, except in a true human nature” quoted by Aquinas in Summa Theologiae, underscoring that the Son of God took on our full humanity (apart from sin) in order to be born and suffer for us. Furthermore, Fulgentius espouses the Theopaschite formula (then current in his time): although the divine nature itself cannot suffer or die, the one divine Person of the Son did truly suffer in the flesh. He explains that Christ’s Passion belonged to “His whole person, but qua nature it was the experience of His flesh only” – at the Crucifixion, Christ’s human soul and body were separated in death, yet His divine nature remained omnipresent and immortal, one with the Father and Spirit as explained by CCEL. This careful phrasing (“one of the Trinity suffered in the flesh”) aligns with the orthodox, Cyrillian-Christology that Fulgentius and his contemporaries (the Scythian monks) defended. We also see an affirmation of Mary’s divine motherhood implicit in Fulgentius’s Christology (since in condemning Nestorius he upholds that the one person born of Mary is truly God). Overall, De Fide presents a concise summary of Catholic Christology, balancing the truths of Christ’s two natures and one person in order to refute all christological heresies of his day.

Soteriology and the Church

Although De Fide is primarily an anti-heretical doctrinal summary, it also contains important soteriological assertions. Fulgentius was a devoted follower of St. Augustine’s theology of grace and salvation, and this influence shows in his emphases on the necessity of faith and the Church for salvation. He teaches that faith in Christ is the indispensable condition for salvation, even more fundamental than the external rite of baptism in itself as highlighted by CCEL. Addressing a question about an unbaptized catechumen, Fulgentius insists that both faith and baptism are ordinarily required – “faith is the indispensable condition of salvation, baptism or no baptism” – and that even baptism will not save a person who lacks true faith according to CCEL. In the treatise he makes a sweeping statement that no heretic or schismatic can be saved while outside the Catholic Church, even if they have received baptism as stated in CCEL. This reflects the classic North African view of “extra Ecclesiam nulla salus”: the charity and even martyrdom of someone separated from the Church “are of no avail, since they are separated from the Catholic Church” per CCEL. Fulgentius argues that those who deliberately adhere to heretical doctrine (such as Arians, Macedonians, etc.) forfeit salvation unless they are reconciled to the true Church according to CCEL. His soteriology is thus tightly bound to orthodox faith and Church unity.

In line with Augustine’s teaching, Fulgentius also upholds the doctrine of original sin and the absolute need for God’s grace. While De Fide itself focuses on refuting heresies about God and Christ, Fulgentius’s wider theology (expressed in contemporary works) informs its perspective: he taught that all humans are born in sin and require Christ’s redeeming grace, normally bestowed through baptism as Encyclopedia.com explains. He went so far as to assert that even infants who die unbaptized cannot reach heaven – a rigorist Augustinian position – though their punishment he held to be milder than that of those who willfully sinned according to Encyclopedia.com. This austere view underlines his conviction that salvation is entirely a gift of God’s grace, not attainable by human effort alone. In De Fide, he likely alludes to this by condemning the Pelagian error implicitly (Pelagianism being the denial of original sin and the necessity of grace). Indeed, elsewhere Fulgentius and his fellow bishops explicitly anathematized Pelagius and his followers as noted by CCEL, and De Fide echoes the same spirit by crediting all merit to divine grace and warning that even good deeds “of heretics” avail nothing apart from true faith per CCEL. Finally, Fulgentius’ soteriology has an eschatological edge: he reminds his readers of the finality of God’s judgment – at death one’s soul’s state is fixed forever according to CCEL. Thus, De Fide not only outlines what to believe about the Trinity and Christ, but also underscores the stakes: only by holding the true faith and remaining in Christ’s Church can one attain eternal salvation.

Historical Context and Doctrinal Controversies

Late 5th–Early 6th Century North Africa and Arianism

St. Fulgentius composed De Fide during a turbulent period for the Church in North Africa. The region was under the rule of the Vandals, a Germanic people who adhered to Arian Christianity and often persecuted Nicene (Catholic) Christians. Fulgentius himself, soon after becoming Bishop of Ruspe in 507, was exiled by the Arian Vandal king Thrasamund along with dozens of other bishops as Encyclopedia.com records and Britannica confirms. He spent years (508–515 and 517–523) in exile on Sardinia, during which time he carried on an active correspondence and wrote treatises to strengthen his fellow Catholics. De Fide likely emerged in this context – scholars date it around c. 519–520, when Fulgentius was addressing both the Arian challenge and other doctrinal issues. The immediate impetus, according to the dedication, was to refute Arian arguments that were troubling the faithful. Arian clergy in Africa would engage Catholics in debate, raising objections about the Trinity (e.g. arguing against Christ’s equality with the Father). Fulgentius, as an expert in Augustine’s theology and the Nicene tradition, responded by providing a comprehensive “rule of faith” that could be used to answer Arian claims according to CCEL. In doing so, he also took the opportunity to catalogue other heresies (Sabellian, Macedonian, Nestorian, etc.) so that the orthodox believer would be equipped against all deviations.

This treatise thus serves as an anti-heretical handbook in an era when orthodox doctrine needed vigorous defense. The Arian controversy was still very much alive: even though Arianism had been condemned in the 4th century, it remained the creed of Vandal rulers. Fulgentius’s theological heroes were Athanasius and Augustine, and he consciously continued their battle against Arian Christology. In fact, King Thrasamund himself was curious enough about Catholic teaching that he posed a series of ten questions to Fulgentius; the bishop answered with another work (Contra Arianos and Ad Thrasamundum in three books) expanding on Trinitarian proofs as Encyclopedia.com notes. De Fide is shorter than those works, but it overlaps in purpose. It reflects the post-Chalcedon, post-Nicene consensus that Fulgentius was upholding: one God in Trinity, and Christ one person in two natures. Additionally, an important Eastern controversy of Fulgentius’s time was the Theopaschite dispute – whether one of the Trinity truly suffered on the cross. In 519, a group of Scythian monks advanced the formula “One of the Trinity suffered in the flesh,” seeking support from Rome and African exiles. Fulgentius was a leading voice in favor of this formula, which he and 15 other exiled African bishops endorsed in a letter (Ep. 17) as Encyclopedia.com mentions and CCEL confirms. The ideas from that debate – particularly the careful explanation of how Christ’s divine nature remains impassible even as His person experiences death – found their way into De Fide as CCEL explains. Thus, the treatise stands at the crossroads of Western and Eastern doctrinal currents: while primarily fighting Arianism, it also confirms the Council of Chalcedon (451) against Monophysitism and echoes the emerging consensus of 6th-century Christological formulae.

Augustine’s Legacy and the Semi-Pelagian Controversy

Another vital aspect of the historical backdrop is the ongoing struggle over Augustine’s doctrine of grace and free will, often termed the Semi-Pelagian controversy. Fulgentius lived about a century after St. Augustine and became known as “the abbreviated Augustine”, so thoroughly did he follow Augustine’s theological line as Britannica notes. In Gaul (southern France) during Fulgentius’s lifetime, many monks and some theologians (like Faustus of Riez) advocated a mitigated form of Pelagianism – they accepted original sin and the need for grace, but maintained that the first steps toward faith could come from human free will and that predestination was based on God’s foreknowledge of human merit. Fulgentius, in his extensive correspondence and treatises (e.g., De Veritate Praedestinationis et Gratiae in 3 books, and letters Ad Monimum), emerged as a key champion of Augustinian predestinarian theology against these views as Encyclopedia.com explains. While De Fide itself is aimed at summarizing the “rule of faith” and doesn’t delve deeply into questions of predestination, it presupposes the soteriological framework that Fulgentius defended elsewhere: namely, that salvation is entirely God’s work of grace, from start to finish, and human beings cannot save themselves. In the treatise, this comes across in the stark exclusion of heretics and unbelievers from salvation (underscoring the necessity of God-given faith), and in the notion that even virtuous acts mean nothing without true faith – implying that faith itself is a gift, not a mere human achievement.

During Fulgentius’s final years, the Semi-Pelagian debate was reaching a resolution. In 529 (shortly after Fulgentius’s death), the Second Council of Orange formally condemned Semi-Pelagian teachings and affirmed a modified form of Augustinianism. It’s notable that Orange’s canons closely reflect positions Fulgentius and the Scythian monks had taken: for example, Orange taught that even the beginning of faith is a result of prevenient grace, and it rejected the idea that “all” are saved without respect to God’s grace. Fulgentius had argued, in agreement with Augustine, that when Scripture says God wills “all men to be saved,” it means all kinds of men rather than every individual according to CCEL. This interpretation, which “weakened the universalism of God’s love” in the words of one historian quoted by CCEL, was aimed at upholding God’s sovereignty in salvation – a hallmark of Fulgentius’s theology. Indeed, Fulgentius taught that God’s will is ultimately decisive: “God’s will determines one’s predestination to glory or damnation”, as the Catholic Encyclopedia summarizes his view, though always in a way that is just and not apart from foreknowledge of demerits as Encyclopedia.com explains. Such strong predestinarian language was controversial, but Fulgentius carefully avoided attributing evil to God; he contended that God predestines the good to salvation while those who are lost are justly permitted to fall (a distinction later councils would maintain).

In sum, De Fide was written at a time when orthodox Catholic doctrine was contested on multiple fronts. Fulgentius addresses the Trinity and Incarnation primarily, due to the Arian and Monophysite pressures, but the treatise’s stern tone on salvation and the Church also reflects the intensity of the Semi-Pelagian dispute. North Africa’s exiled bishops, under Fulgentius’s leadership, stood as a bulwark of Augustinian orthodoxy during this era according to Britannica. Fulgentius’s De Fide can thus be seen as a product of its time: a late antique synthesis of doctrinal truth meant to shore up the faithful against erroneous currents both old and new.

Structure and Rhetorical Strategies of the Treatise

Structure: De Fide is a relatively brief, single-book treatise (sometimes classified as Epistula VIII in Fulgentius’s letter collection) that nevertheless covers a wide array of doctrinal topics in a logical sequence. It functions almost like a creedal summary or catechism, proceeding through the core tenets of the Catholic faith and refuting corresponding heresies point by point. The work is often described as an “anti-heretical compendium” of doctrine according to Brill. Medieval readers noted that it is divided into approximately 18 sections or chapters, each dealing with a particular aspect of the faith as Brill mentions. Fulgentius likely begins with the unity of God and the Trinity, then moves to Christ’s incarnation, and so forth – essentially following the outline of the rule of faith. For example, one section defines the Trinity to counter Sabellius and Arius, another section discusses the Son’s incarnation and birth to counter Photinus and Nestorius, and another affirms Christ’s suffering, death, and resurrection (against those who would deny the reality of His human experiences). The treatise does not explicitly label these as separate “chapters” in the original, but later editors (and the Patrologia Latina edition) number the paragraphs for ease of reference. This systematic approach means the text reads as a series of doctrinal propositions each followed by succinct refutations of errors. Indeed, Fulgentius systematically names the heresies he is rebutting – e.g. “Sabellian, Arian, Macedonian, and Manichean heresy” are each introduced and succinctly characterized as CCEL notes – and then he states the orthodox position in contrast. This clarity of structure made De Fide a very handy digest of doctrine for later generations (as we will see in its reception). In effect, Fulgentius created a mini-“handbook of faith”. It became known also by the title De regula fidei (“On the Rule of Faith”) according to Vatican.va and Encyclopedia.com, indicating its structured, almost list-like presentation of the fundamentals of Catholic belief.

Rhetorical Strategies: Fulgentius’s style in De Fide is concise, direct, and authoritative. He writes in the mode of a bishop instructing his flock, frequently using imperatives and formulaic phrases to drive home non-negotiable truths. One characteristic device is the repetition of exhortatory phrases such as “Hold most firmly that…” or “Believe without doubting that…”. For example, surviving references show phrases like “Principaliter tene…” (“Hold primarily that…”) and “Firmissime tene…” (“Hold most firmly…”) introducing key doctrines as Andrew Jones notes. This rhetorical strategy serves to underline the certainty of each article of faith and to invite the reader to assent wholeheartedly. Each section often begins by positively stating the true doctrine, then negating the false teaching. For instance, Fulgentius will assert the one essence and three persons of the Trinity, and immediately follow with a rejection of Sabellian conflation and Arian subordination as CCEL explains. Similarly, after explaining Christ’s two natures in one person, he explicitly says the Church “declares” (or “teaches”) this and “condemns” the contrary errors of Nestorius and Eutyches according to CCEL. This dialectical format (thesis followed by antithesis) gives the treatise a sharp clarity and was likely intended to be easily memorized or noted for apologetic use.

Scripture and earlier patristic authority are present but used in a targeted way. Fulgentius was well-versed in the Bible (he had even memorized large portions of it as a monk according to CCEL), and he does bring in biblical support for doctrines – for example, he engages with John 1:1 to counter the Arians as CCEL notes, and he might cite texts like John 10:30 (“I and the Father are one”) or other Trinitarian proof-texts in support of consubstantiality (though the extant summaries focus on his arguments rather than direct quotes). He also inherited Augustine’s habit of reasoning about doctrine. In one case, addressing the Arian misuse of “with God” (apud Deum), Fulgentius employs an “argumentum ad hominem” – taking the opponent’s premise and showing it leads to an absurdity as CCEL describes. Wace’s analysis notes that Fulgentius’s clever logical rebuttal of the Arian reading is “very ingenious,” even if the subsequent exegetical explanation is somewhat strained according to CCEL. This tells us Fulgentius combined rational argumentation with authoritative assertion. His tone remains pastoral and firm; he is not merely speculating, he is defending what the Church “holds and believes.” The treatise likely closes with an exhortation to adhere to this true faith unto salvation, reinforcing the pastoral purpose behind the polemic.

Another notable strategy is Fulgentius’s inclusion of multiple heresies across the theological spectrum, creating a sort of catalogue of errors with the Catholic response to each. For example, besides Trinitarian and Christological heresies, he even touches on Manichaeism according to CCEL. In refuting Manichean dualism, Fulgentius asserts the goodness of creation and the single origin of all things in the one God, stating, for instance, that “there is no evil in nature” as created by God as CCEL notes (evil being a privation or a result of sin, not an independent substance). By briefly covering Manichean error, he shores up the doctrine of one all-good Creator – which indirectly also bolsters the case against gnostic tendencies and underscores that the source of evil is the will, not matter. The rhetorical effect of this broad sweep is to present Catholic doctrine as a coherent whole: any deviation at any point (be it about the Trinity, Christ, creation, or grace) is shown to disrupt the unity of the faith. Thus, unity of doctrine mirrors the unity of the Church that Fulgentius is so keen to preserve.

In terms of prose style, contemporaries admired Fulgentius for his “flowing eloquence” and balanced, antithetical style, even in polemical writings as CCEL states. We see touches of this eloquence in De Fide as well. For example, the inscription of one manuscript attributes to Fulgentius the saying “Sola caritas est, quae vincit omnia” (“Only charity is it that conquers all”) found in Wikimedia Commons, which, while not from De Fide directly, reflects the moral exhortation underlying his teaching: love (caritas) holds the faithful in unity against all errors. This blend of theological precision and pastoral earnestness is a hallmark of Fulgentius’s rhetoric. In De Fide, every line is purposeful – either defining a mystery or guarding it from distortion – which is why the treatise became a model of succinct theological instruction in subsequent ages as Brill explains.

Influence on Later Theological Development and Reception

Medieval Reception and Influence

De Fide had a significant afterlife in the Middle Ages, though often under an interesting misattribution. Because of its clarity and authority, the treatise was sometimes transmitted as though it were a work of St. Augustine. In fact, medieval manuscript collections of Augustine’s works included De Fide ad Petrum, and it was long thought to be an Augustinian piece – it appears in Patrologia Latina vol. 40 appended to Augustine according to JSTOR. This confusion testifies to the high esteem in which the text was held: monks and scholars found it worthy of Augustine himself. Under the name “Augustine,” De Fide became a source for theological compendia and was frequently quoted by scholastic theologians. For example, Peter Lombard in the 12th century knew the treatise (likely attributing it to Augustine) and used its Trinitarian teaching in his Sentences. Thomas Aquinas also cites it in the Summa Theologiae: in one instance he explicitly references “Augustine [Fulgentius], De Fide ad Petrum” to support Christological doctrine as seen in NewAdvent. Aquinas quotes Fulgentius’s line that “the eternal Divine Nature could not be conceived and born of human nature, except in a true human nature”, integrating Fulgentius’s formulation into his own argument about the incarnation as cited in NewAdvent. Such usage shows how De Fide helped transmit orthodox patristic theology to the Scholastic era.

Moreover, De Fide served as a model for medieval theological summaries. Scholars observe that it “became the model of medieval compilations of maxims” according to Brill. In the early scholastic period (11th–12th centuries), there was a genre of short theological syntheses (e.g. the Summa sententiarum or various capitula on doctrine). Fulgentius’s De Fide was used as a template by these works; indeed a 1959 study by Aloys Grillmeier demonstrated parallels between De Fide ad Petrum and the Summa Sententiarum, highlighting how Fulgentius’s structured approach influenced the emerging Scholastic method as noted in PhilPapers. Medieval theologians prized the text’s neat organization of dogma, adopting both its content and its format. For instance, the Collectio Palatina (an early medieval collection of doctrinal excerpts) includes De Fide, and an 9th-century manuscript from Würzburg shows excerpts of De Fide copied at the very front, as a kind of doctrinal prologue according to Medieval Bodleian Oxford. This suggests that medieval compilers saw Fulgentius’s statements as authoritative definitions to be learned or used in debate.

In monastic and ecclesiastical education, De Fide likely functioned as a concise summa of basic theology. We see evidence of its widespread presence in the number of manuscripts: it survives in numerous copies across Europe – from a 9th-century codex in Germany to multiple 13th-century manuscripts in England as the Medieval Bodleian Oxford records. Such distribution indicates it was read in Carolingian intellectual circles and beyond. Notably, around 523, after the Vandals’ persecution ended, Fulgentius himself returned to Africa in triumph and held councils as CCEL explains; his writings, including De Fide, would have been circulated among African and Italian churches, and from there to Gaul. By the high Middle Ages, even though the text was under Augustine’s name, it contributed to the consolidation of orthodoxy. For example, theologians discussing the Trinity often echoed Fulgentius’s formulations on the unity of divine essence and distinction of persons, and those discussing Christ cited his authority for the reality of Christ’s two natures. In canon law, the treatise’s stance on heretics’ lack of salvation was sometimes invoked to support ecclesiastical discipline (the principle that heresy cuts one off from the Church’s saving grace).

In summary, throughout the Middle Ages De Fide enjoyed a double life: as an authoritative text in its own right and as a quasi-Augustinian work that bolstered the patristic foundation of medieval doctrine. Its influence on later theology is seen both in the content it transmitted (key Trinitarian and Christological formulas that became standard) and in the method it exemplified (ordered, summary propositions, a forerunner of the scholastic quaestio style). The treatise’s clear-cut pronouncements found their way into many a theologian’s arsenal, ensuring that Fulgentius’s voice – even if not always under his name – guided the Latin Church’s doctrinal understanding well into the Scholastic and even reforming eras.

Modern Scholarship and Legacy

In modern times, De Fide has been studied with interest as a bridge between the patristic age and the early medieval scholastic tradition. Once the true authorship was recognized (scholars of the Maurist tradition in the 17th–18th centuries identified it as Fulgentius’s work rather than Augustine’s), the treatise contributed to a re-evaluation of Fulgentius’s importance. He is now acknowledged as “the foremost North African theologian of his day,” a faithful transmitter of Augustine’s theology according to Francis Gumerlock and Britannica. Patrologists note that De Fide ad Petrum in particular solidified Fulgentius’s reputation as “Augustine’s abbreviator” as Britannica phrases it – essentially condensing Augustine’s vast doctrinal teachings into a handy format. Modern scholarly commentary, such as the introduction by Robert B. Eno to the Fulgentius: Selected Works (CUA Press, 1997), emphasizes how De Fide encapsulates the theological consensus that would dominate Western Christianity: a clear affirmation of trinitarian consubstantiality, Chalcedonian Christology, and Augustine’s soteriology.

Researchers like Aloys Grillmeier have highlighted De Fide’s role in the development of systematic theology, seeing in it an early attempt to systematize doctrine by topics, something that would later be characteristic of the Scholastics as noted in PhilPapers. It’s also studied as evidence of doctrinal continuity – De Fide shows that the theology of Nicaea (325) and Chalcedon (451) was not only maintained but deliberately compiled and handed on in the 6th century, despite political upheavals. Modern historians of doctrine consider Fulgentius a crucial link between the 5th-century Church Fathers and the 6th-century reconciliation of East and West (the formula Unus de Trinitate passus in 519, to which Fulgentius contributed, prefigures some concerns of the Second Council of Constantinople in 553).

In terms of reception, contemporary theologians have revisited Fulgentius for specific questions: for instance, his statements in De Fide about no salvation outside the Church have been cited in 20th-century discussions about baptism of desire and the fate of unbaptized infants. The Vatican’s International Theological Commission document “The Hope of Salvation for Infants Who Die Without Baptism” (2007) references Fulgentius’s uncompromising view to contrast it with later developments as discussed in CCEL. This shows that even today, Fulgentius’s work is part of the historical tapestry that theologians examine to understand the evolution of doctrine and pastoral theology. While modern sensibilities may find some of his positions severe, scholars appreciate that De Fide exemplifies the intellectual rigor and clarity of the late patristic Church.

Critical editions have improved our understanding of the text. The authoritative modern edition of De Fide ad Petrum is found in Corpus Christianorum Series Latina (CCSL) 91A, edited by J. Fraipont (1968) according to Medieval Bodleian Oxford. Fraipont’s work, based on the best manuscript witnesses, cleans up some copyist errors and confirms the authenticity of the text as Fulgentius’s. With this edition and translations into modern languages, De Fide has been made accessible for scholarly analysis. As a result, Fulgentius’s contribution is more widely recognized: he is now seen as a pivotal figure in transmitting orthodox teaching through a very challenging historical period, and De Fide is one of his crown jewels in that regard.

Manuscript and Textual History

De Fide has a fascinating textual history, involving issues of title, attribution, and transmission. In Fulgentius’s own corpus, the work is sometimes listed among his letters. In fact, in some manuscript traditions it is called the “Letter to Donatus on the Faith” (Epistula VIII) according to CCEL. Internal evidence suggests Fulgentius addressed it to a layman (Donatus) or perhaps broadly to the Church in Carthage, answering doubts raised by Arian interlocutors. However, other copies present the work as directed “Ad Petrum” (to Peter). One hypothesis is that “Peter” might have been a recipient or simply an alternate title referring to the Apostle Peter as a symbol of the Church’s faith. The treatise became known as De fide ad Petrum, and under this title it was mistakenly attributed to St. Augustine, possibly because some scribes thought only an authority like Augustine would write such a comprehensive regula fidei. Consequently, during the Middle Ages the text circulated under Augustine’s name, bearing the title Liber de fide ad Petrum, sive de regula verae fidei as JSTOR records. Patrologia Latina volume 40 includes it among Augustine’s works (cols. 753–780) with exactly that attribution according to JSTOR.

It was only later, through the work of scholars (from the Renaissance and especially the Maurist Benedictine scholars), that the true authorship was clarified and the text was restored to Fulgentius. In Patrologia Latina vol. 65, which contains Fulgentius’s opera omnia, De Fide is printed in cols. 671–706 as “Fulgentii Ruspensis Liber de fide seu de regula fidei ad Petrum” as noted by Vatican.va. The PL editors note the duplication and pseudonymous history. Modern critical tools like the Clavis Patrum Latinorum (CPL) assign it number 826 and confirm Fulgentius as author according to Medieval Bodleian Oxford. The CCSL edition (91A) provides the best Latin text (pages 711–760 in that volume) based on a comparison of numerous manuscripts as Medieval Bodleian Oxford confirms.

As for the manuscripts, De Fide is well-attested. Notably, Oxford, Bodleian Library, Laud. Misc. 92 (c. 825–850 AD, produced likely in the monastery of Niederaltaich in Bavaria) contains this work – an indication of its early diffusion into the Carolingian realm as recorded by Medieval Bodleian Oxford. That 9th-century manuscript includes De fide ad Petrum as an extract at the very start (fol. 1r) according to Medieval Bodleian Oxford, paired with other theological pieces, which suggests it was valued as an authoritative prologue. Other English manuscripts from the 13th–14th centuries (e.g., Bodleian MSS. 132, 136, 150, Merton College MS. 1, etc.) list De fide in their contents as noted by Medieval Bodleian Oxford. The sheer number of surviving copies (the Bodleian catalogue alone lists about a dozen) indicates the text’s popularity. Interestingly, some manuscripts explicitly name Donatus as the addressee, while others use Petrus; this likely reflects different lines of transmission. It is possible that an early copy sent to Carthage was described generally as a letter “to the people through Peter” (if Peter was a cleric or deacon who delivered it), or that a scribe confused ad donatum (to Donatus) with datum ad Petrum in a heading. Regardless, by the high Middle Ages the Ad Petrum title stuck in many catalogues.

Textually, there are no major doctrinal variants among the manuscripts – the content remains consistent (any divergence tends to be minor copyists’ slips or variations in chapter division). The critical edition by Fraipont notes some corrections to Scripture quotations and standardized the terminology. For example, if one manuscript lacked a clause or had an obvious interpolation, the editor could compare across copies to restore the original. One interesting phrase from Fulgentius’s letter to the Scythian monks (Ep. 17) – “ex utero Patris” describing the Son’s eternal generation as CCEL notes – is not in De Fide, but the treatise uses more traditional language for the Trinity. Thus, De Fide presents a very stable text doctrinally. The Patrologia Latina edition (based on earlier printed editions from the 17th century, such as Louis Mangeant’s 1684 edition as CCEL mentions) is quite serviceable, though Fraipont’s CCSL offers improvements in Latin readings and layout.

In terms of title, modern scholars typically refer to it as De fide ad Petrum (following longstanding usage) but will note in parentheses that it is the same as Epistle 8 ad Donatum. Some have also called it Regula Fidei Fulgentii. This dual naming in sources is an important point for researchers tracing citations. For instance, older references in ecclesiastical manuals (and in Denzinger’s Enchiridion) might list it under “Augustine, De Fide ad Petrum,” whereas contemporary patristic bibliographies correct it to “Fulgentius of Ruspe, De Fide.” The misattribution persisted for centuries, which ironically amplified its influence (Augustine’s name carried great weight). Today, however, Fulgentius receives proper credit, and the treatise is studied as a shining example of post-Nicene African theology.

In conclusion, De Fide by St. Fulgentius is a compact yet rich theological treatise that distills the fundamental doctrines of Christianity in the face of heresy. It embodies the mature fruit of the patristic era – drawing heavily on Augustine and the councils – and helped to transmit that heritage intact to the medieval Church. Historically, it arose from a context of persecution and controversy, which gives it a notably urgent and polemical tone. Structurally, it is well-organized and rhetorically potent, making complex theology accessible. Its influence resonated through the medieval period (sometimes under another’s name), contributing to the formation of scholastic thought and the continuity of orthodox teaching. Modern scholarship values De Fide as an important link in the doctrinal chain and as testimony to Fulgentius’s role as a guardian of orthodoxy in a transitional age. As one encyclopedia entry succinctly put it, De fide ad Petrum is “a compendium of dogmatic theology” as stated in Encyclopedia.com – one that earned Fulgentius a place among the great doctors of the early Latin Church.

Sources

  1. Encyclopedia Britannica - Saint Fulgentius of Ruspe
  2. Encyclopedia.com - Fulgentius of Ruspe
  3. CCEL - Dictionary of Christian Biography - Fulgentius
  4. Aquinas - Summa Theologiae - Citation of Fulgentius
  5. Brill - Encyclopedia Entry on De Fide
  6. Vatican.va - Reference to De Fide
  7. Andrew Jones - Christian Faith and Demonology
  8. PhilPapers - Grillmeier on Fulgentius
  9. Medieval Bodleian Oxford - Manuscript Catalog
  10. Francis Gumerlock - Transformation of Fulgentius
  11. JSTOR - Zwischen Patristik und Scholastik
  12. Commons Wikimedia - Fulgentius Portrait