Johann Weyer: The Physician Who Called Witches Deluded, Not Guilty

The short answer

Johann Weyer (also Wier or Wierus; born 1515 or early 1516 in Grave on the Meuse, died 24 February 1588 in Tecklenburg) was a physician from the Duchy of Brabant who served from 1550 as personal physician to Duke Wilhelm the Rich of Jülich-Cleves-Berg. His De praestigiis daemonum ("On the Tricks of Demons"), printed in Basel in 1563 by Johannes Oporinus, is the first large, systematic book against the witch trials. It went through six Latin editions by 1583 and was translated into German and French within his lifetime.

His argument was theological and medical at once: the devil needs no human helpers, so the "witch" who confesses is his victim, not his partner. The same book also contains the list of demons that later grew into the Ars Goetia — printed, by Weyer's own account, to expose conjurers, not to equip them.

Agrippa's pupil — with or without a doctorate?

Weyer was the son of a merchant in Grave. The most recent reference entry, by Hans de Waardt in the Neue Deutsche Biographie (vol. 28, 2024), dates his birth between 24 February 1515 and 24 February 1516. From 1529 he was taught by Heinrich Cornelius Agrippa of Nettesheim in Antwerp and Mechelen and followed him to Bonn in 1532, where Agrippa lived under the protection of the archbishop-elector Hermann von Wied.

He then studied medicine in Paris. Here the reference works part ways. Carl Binz, in the Allgemeine Deutsche Biographie (vol. 42, 1897), has him take his doctorate at Orléans in 1537. De Waardt states the opposite: Weyer earned a doctorate neither in Paris nor in Orléans. We cannot settle this and do not try; the newer entry reflects newer research, but the older claim is repeated almost everywhere online.

The career itself is undisputed. In 1545 Weyer became town physician of Arnhem; in 1550 he moved to the court of Jülich-Cleves-Berg at Düsseldorf and Cleves. He retired from court service around 1578 — his son Galenus succeeded him as ducal physician — and died ten years later while visiting the family of the Count of Tecklenburg, where he was buried in the castle church. Neither church nor grave survives. In 1884 the town built a small tower from the castle's stones as a memorial, the Wierturm, which still stands.

Weyer also wrote as an ordinary doctor: a volume of medical observations (1567) on scurvy, fevers and epidemics, a treatise on anger as a disease, and a short book exposing fraudulent "miraculous fasting."

What De praestigiis daemonum argues

Binz reports that Weyer wrote the book in 1562 at the ducal castle of Hambach near Jülich. The dedication to his duke is signed "Ioan. Vuierus Medicus." In the preface Weyer explains why a physician should meddle in a question for theologians and lawyers: part of the matter is medical, because illnesses "wrongly imputed" to witches arise according to the laws of nature.

The core distinction runs through the whole book. There are the magi infames, the "infamous magicians": educated men, often clever, who travel to learn a demonic art from books, circles and characters. And there are the lamiae, the women accused as witches. They, Weyer writes in the 1563 text, are "for the most part women, and old ones, unsteady of mind" (ut plurimum feminae, eaedemque vetulae et mente titubantes), whose imagination the devil occupies "in the disease of melancholy, in grief or in extreme despair," until they believe they did whatever harm he shows them.

Three consequences follow. The confessions prove nothing, because the mind that produced them is damaged. The harm attributed to witches has natural causes a physician can name. And the women should be instructed and cared for rather than executed. Weyer did not, however, abolish punishment altogether: the sixth book, by his own preface, discusses how to punish the infamous magicians and the venefici — people who actually poison — "according to the kind and size of the offence."

For readers of our article on Giambattista della Porta: Weyer quotes Porta's witches' ointment chapter from Magia naturalis Book II already in the 1563 first edition, five years after Porta printed it, calling him a most skilful investigator of hidden causes. The ointment and the deep sleep fitted his thesis perfectly — flight as a dream, not a crime.

The teacher, his "trifles" and his black dog

Weyer's loyalty to Agrippa is often described as simple discipleship. The printed text is more interesting. In the 1563 edition, discussing charms made from the bones of the dead, he writes that "with the good leave of my former master and venerable teacher Agrippa, who patched together a book out of these trifles," he freely declares such things to be empty. The book in question is De occulta philosophia. Weyer respected the man and dismissed the magic — and elsewhere he rejected the spurious "Fourth Book" circulating under Agrippa's name, as our article on Agrippa's Three Books explains.

Later editions add a passage that folklorists still cite. A rumour held that Agrippa's black dog had been a demon that stayed with him to his last breath and then vanished. In the final edition (Book II, chapter 5; we read it in the 1583 printing) Weyer answers from experience: the dog was black, of middling size, called "Monsieur" in French, and he knew it as well as anyone, because he often led it on a leash. It was an ordinary male dog; Agrippa had paired it with a similar bitch called "Mademoiselle." The rumour, Weyer thought, came from his master's excessive fondness — he kissed the dog and let it lie beside him at table and at night — and from the fact that Agrippa, who hardly left his study for days, still knew the news of distant countries. The explanation: scholars wrote to him daily.

The folklorist Willem de Blécourt has traced how this dog story wandered into the Faust tradition, where the Swiss pastor Johannes Gast already gave Faust a demonic dog in 1548. Goethe's black poodle of 1808 is its most famous descendant.

Faust at Batenburg

Weyer is also one of the few sixteenth-century authors who writes about the historical Faust. In the 1583 edition, in the chapter on infamous magicians, he describes a Johannes Faustus from the small town of "Kundling" — usually identified as Knittlingen — who learned magic in Kraków, "where it was once taught openly," and a few years before 1540 practised lies and fraud in various places in Germany to general amazement; in empty boasts and promises, Weyer adds drily, there was nothing he could not do. Weyer places him at Batenburg on the Meuse, at the border of Guelders, where Faust was arrested for some offence while the lord of the place, Baron Hermann, was away, and treated gently by the chaplain Johannes Dorstenius.

Two cautions. Our full-text search of the digitized 1563 first edition does not find the Faust passage, so it belongs to the expanded later editions; and the digitized texts are raw OCR of Renaissance Latin, which can miss words. Weyer's Faust is not the tragic scholar of later literature but a boastful impostor — exactly the "infamous magician" his book warns against.

The demon list he printed to discredit

In the fifth edition of 1577 Weyer added an appendix, the Pseudomonarchia daemonum, the "false monarchy of demons." It lists spirits with ranks, appearances and numbers of legions, beginning with "Bael," a king with three heads. His introduction states the purpose: to expose the curiosity, deceit, vanity, fraud and delusion of those "who are not ashamed to call themselves magicians." He says he deliberately left out words and formulas so that every occasion for wrongdoing would be cut off, and names his source as a manuscript called Liber officiorum spirituum.

How that list — 69 spirits in Weyer — became the 72 spirits of the Ars Goetia, complete with seals and conjurations restored, is told in our article Ars Goetia: where the 72 demons came from. For this portrait one detail matters: the opponents who called Weyer a friend of sorcerers used exactly this appendix against him.

Bodin, the Index and the backlash

The French jurist Jean Bodin attached a "Refutation of the opinions of Jean Wier" to his De la démonomanie des sorciers (Paris, 1580). In the 1580 text he grants that Weyer's books show he is no ignorant man, and a physician besides — and then accuses him of teaching "a thousand damnable" things, printing the words, invocations, figures, circles and characters of the greatest sorcerers. At the end of the book, Bodin complains, Weyer put an "inventory of the diabolical monarchy" with 72 princes and 7,405,926 devils, counted at 6,666 per legion — "sauf erreur du calcul," barring a mistake in the arithmetic.

Bodin was not alone. The Jesuit Martín Delrio attacked Weyer at length; Binz lists theologians, jurists and even physicians among his opponents, and records that the book was placed on indexes of forbidden books in Antwerp, Munich, Rome, Spain and Portugal. On the other side, the Englishman Reginald Scot built his Discoverie of Witchcraft (1584) largely on Weyer, and German writers such as Hermann Witekind followed him.

Did the book save lives? Weyer believed so. In the preface to his abridgement De lamiis (1577) he thanks God that certain high authorities now treated the accused women more mildly and even spared them the death penalty. That is his own claim, and no one has counted the cases. The 2024 reference entry judges more soberly that his plea for tolerance did little to stop trials, and Binz records that witch burnings returned to Jülich-Cleves-Berg in Weyer's own old age.

"Father of psychiatry"? A 1930s label

Much of Weyer's modern fame comes from the twentieth century. In his 1935 lectures, published as The Medical Man and the Witch During the Renaissance, the psychoanalyst Gregory Zilboorg presented him as a founder of modern psychiatry, and histories of psychiatry long repeated the idea.

Historians have been cooler. In 1977 Thomas J. Schoeneman reviewed the evidence in the Journal of the History of the Behavioral Sciences and concluded that the role of mental disorder in the witch hunts "has been overinflated by authors with an interest in promulgating the medical model of abnormal behavior." Weyer himself would have been puzzled by the label. His melancholy is the humoral illness of Galenic medicine, and his explanation is not a brain disease but the devil, who deceives a weakened imagination. He was an enlightened critic of the trials inside a demonology, not outside it.

Where the sources disagree

Question	What the sources say
Birth	1515 (ADB 1897, most encyclopedias); between 24 Feb 1515 and 24 Feb 1516 (NDB 2024).
Doctorate	Orléans, 1537 (ADB 1897); none, neither in Paris nor Orléans (NDB 2024).
Start of medical studies in Paris	1534 (ADB); 1533 (NDB).
Travels to Tunis and Crete	Reported by early biographers; Binz (ADB 1897) says they never happened and arose from misread passages.
Danger to his life in retirement	Claimed in 19th-century publications; Binz found no source for it.
Number of spirits	69 entries in Weyer's list; Bodin (1580) speaks of 72 princes.
The duke's number	"Wilhelm III" (ADB) or "Wilhelm V" (common today) — the same Wilhelm the Rich.

Frequently asked questions

Who was Johann Weyer?

A physician (1515/16–1588) from Grave in Brabant, pupil of Agrippa and court physician to Duke Wilhelm the Rich of Jülich-Cleves-Berg, best known for De praestigiis daemonum (1563), the first large book against the witch trials.

What does De praestigiis daemonum argue?

That most women accused as witches were old, confused and melancholic people deceived by the devil, that their confessions prove nothing, and that they needed care rather than execution. Weyer still regarded learned magicians and actual poisoners as punishable.

Did Johann Weyer believe in demons?

Yes. His whole explanation depends on the devil deceiving the imagination. He denied that witches could do what they confessed, not that demons existed.

What is the Pseudomonarchia daemonum?

An appendix to the 1577 edition listing 69 spirits with ranks and legions, printed to expose conjurers. Formulas were deliberately left out. It became a main source of the later Ars Goetia.

What did Weyer say about Agrippa's black dog?

That it was an ordinary dog called Monsieur, which he often walked on a leash himself, not a demon. The passage is in Book II, chapter 5 of the final edition.

Is Weyer the father of psychiatry?

That label goes back mainly to Gregory Zilboorg (1935). Historians such as Thomas Schoeneman (1977) have criticized it as projecting modern psychiatry onto the witch trials.

Sources

Johann Weyer, De praestigiis daemonum, Basel: Oporinus 1563 (Internet Archive, Getty Research Institute copy) and sixth edition 1583 with Liber apologeticus and Pseudomonarchia daemonum (Internet Archive, Biblioteca Nazionale Centrale di Firenze) · Hans de Waardt, "Wier, Johann," Neue Deutsche Biographie 28 (2024), pp. 96–97 (deutsche-biographie.de) · Carl Binz, "Weyer, Johann," Allgemeine Deutsche Biographie 42 (1897), pp. 266–270 (Wikisource) · Jean Bodin, De la démonomanie des sorciers, Paris 1580, "Réfutation des opinions de Jean Wier" (Internet Archive) · Willem de Blécourt, "A Man and His Dog" (ISFNR) · Thomas J. Schoeneman, "The role of mental illness in the European witch hunts of the sixteenth and seventeenth centuries: an assessment," Journal of the History of the Behavioral Sciences 13 (1977), 337–351 · Gregory Zilboorg, The Medical Man and the Witch During the Renaissance (1935) · George Mora et al. (eds.), Witches, Devils, and Doctors in the Renaissance (1991), the standard English translation (listed for readers; our quotations are from the Latin) · Tecklenburg Touristik, "Die Burg" (Wierturm, 1884) · Wikipedia, "Johann Weyer" and "De praestigiis daemonum" (as a register of the literature).

Further reading on this site: Giambattista della Porta and the witches' ointment · Ars Goetia: where the 72 demons came from · Agrippa's Three Books of Occult Philosophy · Johannes Praetorius and the Blocksberg · Flying ointment: what was really in it