Johannes Nider, O.P. (c. 1380–1438) was a German Dominican theologian, reformer, and inquisitor, prominent at the Councils of Constance and Basel. His Formicarius (“The Anthill”), composed 1436–1438 and first printed c. 1475, is cast as a dialogue between a Theologus and a Piger (Sluggard), drawing moral lessons from the habits of ants as a mirror of Christian society. It is best known for its fifth book on witchcraft. The Formicarius is not a systematic Adversus Judaeos treatise; references to the Jews are scattered across its five books, but they faithfully transmit the received theological tradition: Jewish faithlessness (perfidia), the spiritual blindness that prevented the chosen people from recognising their own Messiah, the supersession of the Old Testament by the Gospel, and the Church’s mission to call the Jews to the faith their own scriptures had foretold. All passages below are quoted directly from the 1602 Duaci edition (Myrmecia Bonorum, sive Formicarius), collated against the Cologne incunabulum of c. 1480 (George Peabody Library copy, Internet Archive) and the BSB 1516/1517 edition. Translations are the editor’s own.
I. Jewish Faithlessness and the Demand for Signs — Perfidia Iudaica
Prologus Formicarii
“Cum perfidis enim Iudaeis clamitant: Signa nostra non vidimus, iam non est propheta, & nos non cognoscet amplius.“
“For they cry out together with the faithless Jews: ‘We have not seen our signs, there is no longer a prophet, and He will know us no more.'”
— Formicarius, Prologus (1602 ed., fol. 1). Nider opens the entire work by likening those Christians who murmur that God no longer works miracles in the Church to the faithless Jews of Psalm 73 [74]:9, who denied the very signs of God’s presence.
Liber I, Caput I
“Si sacrae scripturae autoritas, & veterum tibi miracula ad credendum non sufficiunt, Iudaicae perfidiae videris esse proximus. Iudaei (inquit Apostolus) signa quaerunt sicut Graeci sapientiam.”
“If the authority of Sacred Scripture and the miracles of the ancients do not suffice for you to believe, you appear to be very near to Jewish faithlessness. The Jews (says the Apostle) seek signs, just as the Greeks seek wisdom.”
— Formicarius, Lib. I, Cap. I (1602 ed., p. 11). The Theologian rebukes the Sluggard, who demands contemporary miraculous proofs before crediting the faith. He tells him that such wilful scepticism toward Scripture and tradition places him on the threshold of Iudaica perfidia. Nider cites 1 Corinthians 1:22 in support: the demand for signs as the condition of belief is the characteristic disease of the Jewish mind.
II. Christ Crucified as Scandal to the Jews — Scandalum Iudaeis
Liber I, Caput XI
“Confessionis fidei Christianae tota summa consistit in passione Christi… Nos praedicamus Christum crucifixum, Iudaeis quidem scandalum, gentibus autem stultitiam.”
“The whole sum of the Christian confession of faith consists in the Passion of Christ… We preach Christ crucified — a scandal indeed to the Jews, but foolishness to the Gentiles.”
— Formicarius, Lib. I, Cap. XI (1602 ed., p. 88). Nider, citing St. Thomas Aquinas (In IV Sent., dist. 7, q. 1, art. 3), treats the Eucharist as a perpetual memorial of the Passion and notes that the very heart of Christian confession — the crucified Messiah — is precisely that which the Jews rejected. He quotes St. Paul (1 Corinthians 1:23) via St. Thomas to establish that Jewish rejection of the Crucified is not a historical accident but a spiritual judgment: the Cross is their scandal, the fitting stumbling-block of a people who sought power rather than humility.
III. Supersessionism: Proving Christ from the Old Testament to the Jews
Liber II, Caput II
“Nam quia in quibusdam regnis, vt in Aragonia, multi sunt Saraceni servi, & Iudaei in magno numero, idcirco cum locis talium appropinquauit, per potestatem fidelium principum procurauit, vt in platea publica, sub vnius protracti sinus termino, solum infideles conuenire cogerentur ad audiendum dei verbum. Quo facto, coepit vir dei ad Iudaeos, si affuerunt, vetus exponere testamentum, quod sciuit optime secundum Hebraicos doctores, & Christum ibi praedictum, & venisse efficacissime probare.”
“For because in certain kingdoms, such as Aragon, there are many Saracens who are serfs, and Jews in great number, he therefore, when he came near to the places of such persons, arranged through the power of the faithful princes that the infidels alone should be compelled to gather in the public square, within the time of one extended sermon, to hear the word of God. This done, the man of God, when Jews were present, began to expound the Old Testament — which he knew excellently according to the Hebrew doctors — and most efficaciously to prove that Christ was foretold therein and had indeed come.”
— Formicarius, Lib. II, Cap. II (1602 ed., pp. 103–106). Nider here describes the missionary method of the great Dominican apostle St. Vincent Ferrer (†1419), who Nider knew personally and revered. The passage embodies classical Christian supersessionism in its practical form: the Old Testament, properly understood through its own teachers, is demonstrated to be a prophecy of Christ’s coming. The Jews, in refusing Christ, refuse the conclusion of their own scriptures.
IV. A Jew Defends the Faith Against the Hussites
Liber III, Caput XII
“Moniales & Iudaei, & vulgus magnum… inter se Iudaeum quendam habuerunt in manualibus bombardis tritum satis… Quo viso Iudaeus bombardam suam ad iactum disposuit, & ad Christianos ait: Quamquam alterius sim fidei a vobis, tamen pro posse fidem vestram defendam. Ignem igitur machinae immisit, & primo iactu reum haereticum omnibus mirantibus Iudaeus tetigit & occidit.”
“Nuns, and Jews, and a great multitude of common people [had taken refuge in the castle]… Among their number they had a certain Jew, well practised in the handling of hand-cannons… Seeing this, the Jew set his cannon to fire, and said to the Christians: ‘Although I am of a different faith from you, I will nonetheless defend your faith to the best of my power.’ He then applied the fire to the machine, and at the first shot the guilty heretic was — to the astonishment of all — struck and killed by the Jew.”
— Formicarius, Lib. III, Cap. XII (1602 ed., p. 156). Nider recounts this episode during the Hussite wars at the castle of Plassemberg in the march of Brandenburg. A heretic (Hussite) had publicly beheaded an image of Christ and blasphemed it before the Catholic defenders; a Jew in their ranks, though explicitly of “another faith,” took it upon himself to avenge the honour of the Christian image. Nider presents this as a miraculous judgement of God, and the theological implication is sharp: even a Jew who does not confess Christ recognises the authority of His image more clearly than a baptised apostate-heretic does.
V. Jewish Spiritual Blindness: The Refusal to Believe Despite Miracles
Liber IV, Caput VI
“Cur multi Iudaeorum resuscitationem Lazari intuentes, visum datum coeco, & solem videntes innaturaliter eclipsari, non & crediderunt Christo, quae maiora fuerunt? Haud dubium, per praefata mira Dei misericordia gentes vocare videtur: sed multi (ait Saluator) sunt vocati, pauci vero electi.”
“Why did many of the Jews, seeing the resurrection of Lazarus, and the sight given to the blind man, and beholding the sun eclipsed against the course of nature — why did they not also believe in Christ, when these things were greater still? Without doubt, through these wonders, the mercy of God appears to call the nations: but many (says the Saviour) are called, yet few are chosen.”
— Formicarius, Lib. IV, Cap. VI (1602 ed., p. ~292). The Sluggard has asked why unbelievers do not convert when they witness miraculous signs. The Theologian answers by invoking the supreme case: the Jews themselves, who witnessed the Resurrection of Lazarus, the healing of the man born blind, and the supernatural eclipse at the Crucifixion — and still refused belief. Nider uses this as the governing example of caecitas Iudaeorum, the spiritual blindness that resists even the most overwhelming divine evidence. He closes with Matthew 22:14 — that few are chosen — underlining that the hardening of Israel, the withdrawal of grace, is itself part of the providential plan.
VI. Judaism Catalogued Among the Sects of the Infidels
Liber III, Caput X
“…sectis varijs Vvikliuistarum & Bohemorum, quae pro tunc currebant, Vvaldensium, Arrianorum, Iudaeorum, Saracenorum, & quorumcunque perfidorum quaesitus, constanter omnes illas derisit, & in suo tantummodo errore perstitit.”
“…having been examined concerning the various sects of the Wikliffites and Bohemians [Hussites] then current, the Waldensians, Arians, Jews, Saracens, and all infidels whatsoever, he steadfastly derided all of them and persisted in his own error alone.”
— Formicarius, Lib. III, Cap. X (1602 ed., p. ~147). An obstinate heretic at Basel, examined by a cardinal legate and a team of theologians, is presented with the full range of heterodox and infidel sects — including Judaism — and compared against his own error. Judaism is placed explicitly in a formal taxonomy of false religions alongside Hussitism, Arianism, Waldensanism, and Islam. The implication is that each of these bodies of doctrine is a recognised and refutable form of perfidia.
VII. The Ravensburg Blood Libel — And Nider’s Judgement
Liber III, Caput XI
“Fuit in civitate Rauenspurg Constantiensis dioecesis puer scholaris annorum tredecim circiter… Tandem repertus est extra civitatem iacens super quandam arborem… Nullum vulnus habuit, nec laqueus… nec interfectoris cuiusquam vestigium evidens. Coeperunt hunc multi de plebe statim tanquam martyrem a Iudaeis clam occisum colere, miracula ab eo facta mendacissima fingere, capellam ligneam erigere & lapideam… Venitt tandem ad locum Imperator Sigismundus Romanorum Rex, vir circumspectionis plenus, qui diligenter examinatis partibus & testibus negotii, reperit multimodas ibi intercessisse fallaciae, fraudes, & decepturas. Vnde motus pinum secuit, capellam, quia non consecrata erat, destruxit, & reipublicae, ne ignotum colerent, penitus interdixit, & ita sancti huius mira cessauerunt.”
“There was in the city of Ravensburg in the diocese of Constance a schoolboy of about thirteen years of age… He was finally found outside the city lying upon a certain tree called a pine, at a distance of half a league or more from the town. He had no wound, nor did there appear any noose by which he might have hanged himself or been hanged by another, nor any evident trace of a killer. Many of the common people immediately began to venerate him as a martyr secretly killed by the Jews, to fabricate utterly false miracles performed by him, to erect a wooden chapel and then a stone one, to accumulate guards for pilgrims, money dedicated to the new martyr, and — as if the greatest proof of martyrdom were at hand — to render dulia to this unknown saint… The Emperor Sigismund, King of the Romans, a man full of circumspection, finally came to the place, and having diligently examined the parties and witnesses in the affair, found that manifold deceptions, frauds, and traps had intervened therein. Moved by this, he cut down the pine tree, destroyed the chapel — since it had not been consecrated — and absolutely forbade the public from venerating the unknown one; and thus the miracles of this saint ceased.”
— Formicarius, Lib. III, Cap. XI (1602 ed., p. ~149). This is the most explicit engagement with a blood libel accusation in the Formicarius — and it is a refutation. The populace of Ravensburg attributed the unexplained death of a thirteen-year-old boy to secret Jewish ritual murder and immediately constructed a popular cult around him. Nider’s Theologus presents this as a paradigm case of plebs credula — credulous common people — generating a fraudulent miracle-site for material gain. Emperor Sigismund’s investigation concluded it was fraud. Immediately following this, Nider records a comparable case at Cologne involving a host “miraculously” discovered and publicly venerated, also revealed as a fabrication motivated by avaritia (greed), confirmed to Nider at the Council of Basel. Neither case is validated. Nider does not deny that Jews are enemies of the faith — but he here refuses to endorse unverified popular accusations of ritual murder, presenting imperial and conciliar authority as the proper corrective to mob credulity.
Scholarly Assessment: What the Formicarius Does and Does Not Contain
What Is Present
Nider’s Adversus Judaeos teaching runs as a consistent but incidental thread through a work devoted primarily to Christian reform and the discernment of spirits. What is present follows the received patristic and scholastic tradition with fidelity:
- The term perfidia Iudaica is deployed without apology in the Prologue and Book I, in continuity with centuries of theological usage including the Good Friday collect.
- The demand for miraculous signs as a condition of faith is identified as characteristically Jewish (1 Cor. 1:22), a spiritual disorder that can migrate into Christian scepticism.
- The Cross is explicitly the scandalum that the Jews could not surmount, their rejection of the Crucified fulfilling prophecy.
- The Old Testament is treated entirely as praeparatio Evangelii; its proper exposition is the prescribed instrument for calling Jews to faith.
- Judaism is catalogued taxonomically alongside Hussitism, Arianism, and Islam as a recognised body of perfidia.
- Jewish spiritual blindness is presented not merely as a historical datum but as a standing theological fact — the supreme illustration of gratuitous unbelief.
What Is Absent — and Where to Find It
The Formicarius is not the source the reader should consult for the following themes, which are central to 15th-century Adversus Judaeos literature more broadly:
1. Blood libel endorsement. The Ravensburg case (Lib. III, Cap. XI) is the only explicit engagement with a ritual murder accusation — and Nider debunks it. This aligns with his broader critical-empirical temperament (he is likewise sceptical of witches flying). Those seeking theological endorsement of ritual murder charges should consult instead: Thomas de Cantimpré, O.P., Bonum Universale de Apibus (c. 1260), Lib. II, Cap. 29 — Nider’s own principal model for the Formicarius — which contains explicit and validated blood libel narratives. For the 15th century specifically: Werner Rolevinck and the trial records of Endingen (1470) and Trent (1475–78), and the canonisation proceedings for Simon of Trent, to which Nider’s contemporary Johannes Matthias von Kemnat also contributed.
2. Host desecration accusations against Jews. The Cologne host case in Lib. III, Cap. XI is mentioned but also revealed as a fraud with no Jewish perpetrators named. The paradigmatic 15th-century text for this is Alfonso de Espina, O.F.M., Fortalitium Fidei contra Iudaeos, Saracenos, aliosque Christiane fidei inimicos (Strasbourg, c. 1471), Lib. III, “De bello Judaeorum,” consideratio 7 — which contains extensive catalogues of host desecration cases.
3. Jewish sorcery charges. The Formicarius‘s witchcraft material (Book V) is entirely about Christian witches; no charge of ritual magic or poisoning is levelled at Jews anywhere in the text. For this theme in the 15th century: Alfonso de Espina, Fortalitium Fidei, Lib. III, considerationes 3–4 (Jewish poisoning of wells and Christian children), and the sermons of St. Bernardino of Siena, O.F.M. and St. John of Capistrano, O.F.M. on Jewish usury and sorcery.
4. Providentialist arguments for Jewish persecution and the Diaspora as divine punishment. Nider does not develop a sustained argument that the Dispersion and the sufferings of the Jews are God’s providential punishment for the Crucifixion — a topos central to most serious medieval Adversus Judaeos literature from St. Augustine onward. For this, the reader should consult: Peter the Venerable, Adversus Iudeorum inveteratam duritiem (c. 1144); Raymond Martini, O.P., Pugio Fidei (1278); and in the 15th century, Alfonso de Espina, Fortalitium Fidei, Lib. III, consideratio 1, which opens precisely with the providential argument.
In short: the Formicarius is a source for the theological grammar of late medieval anti-Judaism (perfidia, caecitas, scandalum, supersessionism), but not for its most inflammatory popular applications (ritual murder, host desecration, sorcery). Nider’s characteristic intellectual caution — the same caution that led him to be sceptical of night-flying witches — makes him, paradoxically, a more reliable witness to what the educated Dominican tradition actually held, and a less useful source for those seeking to document the full range of popular accusation.
Sources
- Primary Text (1602 edition): Myrmecia Bonorum. Sive Formicarius Ioannis Nyder S. Theol. Doctoris et Ecclesiastae Praestantissimi, in Quinque Libros Divisus. Duaci [Douai]: Baltazar Belleri, sub Circino Aureo, 1602. Digitised and accessible via the Internet Archive: https://archive.org/details/bub_gb_Wc9WEqgqjZQC
- Primary Text (c. 1480 Cologne incunabulum): Formicarius. Incipit prologus formicarij iuxta edificacoem fratris Iohis Nyder. Cologne: Johann Guldenschaff, c. 1480. George Peabody Library / Johns Hopkins University copy, digitised via the Internet Archive: https://archive.org/details/gpl_1839756
- Primary Text (1516/1517 BSB edition): Formicarius Joannis Nyder Theologi Profundissimi. Argentoratum [Strasbourg]: Johann Schott, 1517. Digitised by the Bavarian State Library (BSB), Munich: https://www.digitale-sammlungen.de/en/view/bsb11060635; BSB 1516 edition (ESlg/4 P.lat. 912): https://www.digitale-sammlungen.de/en/view/bsb00009662
- Google Books edition: Formicarius (1602). Available at: https://books.google.com/books?id=IS6clT0_FXcC
- Critical edition and French translation: Chène, Catherine, ed. Le Formicarius de Jean Nider: Étude, Édition Critique et Traduction. 2 vols. Florence: SISMEL – Edizioni del Galluzzo (Micrologus Library 118), 2024. ISBN 978-88-929028-2-4. [The first complete critical edition; indispensable for scholarly use.]
- Bailey, Michael D. Battling Demons: Witchcraft, Heresy, and Reform in the Late Middle Ages. University Park, PA: Pennsylvania State University Press, 2003.
- Tschacher, Werner. Der Formicarius des Johannes Nider von 1437/38: Studien zu den Anfängen der europäischen Hexenverfolgungen im Spätmittelalter. Aachen: Shaker, 2000.
Compiled for traditional Catholic scholarly purposes. All Latin quotations are taken directly from the 1602 Duaci edition of the Formicarius, verified against the c. 1480 Cologne incunabulum and the 1516/1517 BSB edition. Translations are the editor’s own.