Cornelius Loos, also known as Losaeus Callidius (1546 - February 3, 1595), was a Roman Catholic priest, theologian, and Professor of Theology, and was the first Catholic official to write publicly against the witch trials then raging throughout Europe. For this, he was imprisoned and forced under torture to recant; his work was confiscated and suppressed by Church officials, and the manuscript was lost for almost 300 years.


Cornelius Loos was born in 1546 in Gouda. He was from a patrician family and studied Philosophy and Theology at what is today known as the Catholic University of Leuven. In 1574, Loos and his family were forced to leave for political reasons (primarily the capture of the city by Protestant/nationalist rebels during the Dutch Revolt). After he was ordained as a priest, he was awarded a Doctor of Theology degree in 1578 at the University of Mainz, where he became a Professor of Theology and a vigorous campaigner against Protestant beliefs.

In the 1580s, Loos published a number of works: a prayer book, polemical theological writings against Protestantism, a political work (by subscription) about the Netherlands rebellion, a survey of German Catholic authors, and a pocket Latin grammar book.

In 1585, he moved to Trier, where he observed the witch trials taking place there. Loos first wrote letters to the city authorities, and, failing in that effort, he sought in 1592 to publish a book protesting against the hunts and questioning some of the beliefs of the witch hunters. The attempted publication of De vera et falsa magia (True and False Magic)[1] offended Petrus Binsfeld, the Suffragan Bishop of Trier, and who served as the deputy to Johann VI von Schonenberg, one of the highest-ranking officials in the Holy Roman Empire.

Before the book could be printed, the manuscript copy was seized and Loos imprisoned. He was forced to make a public recantation of his errors on his knees before an assembly of church officials, including the Papal Nuncio, in Brussels on March 25, 1593. The manuscript was believed destroyed by the Inquisition and was lost for 300 years.

De vera et falsa magia discovered

In 1886, George Lincoln Burr discovered the manuscript of True and False Magic in the Jesuit Library in Trier (a remnant of the University, which was dissolved in 1798). Although the title page was missing and no author was listed, Burr was able to authenticate the document by comparing the points made in the text with the points recanted in Loos's confession to the Inquisition. A copy can be found in the rare manuscript collection at Cornell University,[2] and the original is in the Trier Municipal Library.[3]

In the manuscript, Loos argues against the existence of witchcraft and especially against the validity of confessions obtained under torture. (It should be noted that Binsfeld had in 1589 published his own book on witchcraft, in which he supported confessions and denunciations obtained through torture.) In his work, Loos is believed to have been influenced by the arguments of Johann Weyer, a Protestant Dutch physician, who in 1563 put forth a book attacking the persecution of witches while also categorizing kinds of magical demons.[4] After recanting, Loos was under constant watch by religious officials, and was briefly imprisoned several more times, under the accusation that he had relapsed into theological error. This continued persecution was conducted by his nemesis, a priest in the Jesuit order named Martin Del Rio. Loos died February 3, 1595, in Brussels, succumbing to the Plague; Del Rio lamented that Loos had died before Del Rio could have him executed.[5]


Although, as noted above, Loos was not the first to write against the witch hunts, he was the first Catholic priest and theologian to do so, and the first to specifically question the validity of confessions obtained under torture.[6] Even though his work was lost for 300 years, his opponent Martin Del Rio ensured his continuing fame by publishing a book denouncing him, and by summarizing each of his arguments in the recantation he forced Loos to sign.[5]


  1. The Witch Persecution at Trier, George L. Burr, ed., "The Witch Persecutions in Translations and Reprints from the Original Sources of European History", 6 vols. (Philadelphia: University of Pennsylvania History Department, 1898-1912) vol. 3, no. 4, pp. 13-18
  2. Witchcraft : catalogue of the Witchcraft Collection in Cornell University Library / introd. by Rossell Hope Robbins ; ed. by Martha J. Crowe ; index by Jane Marsh Dieckmann. Millwood, N.Y. : KTO Press, 1977.
  3. A History of the Warfare of Science with Theology in Christendom Part Two, p. 356, by Andrew Dickson White, 2004, Kessinger Publishing
  4. The Hanover Historical Manuscripts Project, Jonathon Perry, 2001, Footnote #9
  5. 5.0 5.1 Text of Del Rio’s proclamation
  6. The Catholics the First to Speak Against Witchcraft, New York Times, Wednesday, April 6, 1884, p. 12

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