Jakob Sprenger (1436, Rheinfelden – December 6, 1495, Strasbourg) was a professor of theology, an inquisitor, and a well-known demonologist— a German Dominican, and dean of the University of Cologne. He is considered a co-author of the book “The Hammer of Witches,” written together with prior Heinrich Institoris. However, Sprenger’s work appears to have been limited to an introduction titled “The Apologia.”
Heinrich Kramer (also known as Henricus Institor; 1430, Schlettstadt – 1505, Brno or Olomouc, Bohemia) was a German Dominican friar and the author of “The Hammer of Witches.” (The name form “Institoris” placed on the title page is a Latin genitive—i.e., it reads as: “The Hammer of Witches” by Institor”; often this genitive is mistakenly taken for the nominative form of the name. The Latin word “Institor” is a precise Latin translation of the German word “Kramer,” meaning “merchant of small goods.”)
Heinrich believed he was sent by the Lord himself to cleanse the world of heresy. His first investigation, already in his role as inquisitor, he carried out in the Italian town of Trent. It concerned the murder of the two-year-old boy Simoni(o), which was allegedly done by a group of Jews in the course of a ritual killing. During this investigation, Heinrich Kramer issued a death sentence for nine Jews from Trent, and the murdered child was canonized.
In 1484, the pope signed a document compiled for him by Heinrich Kramer: according to the witch bull, the authorities of Germany had to help the inquisitors in the fight against witches by all means. During Kramer’s time, about 3,000 so-called “witches” died.
“The Hammer of Witches” or “Hexenhammer” is undoubtedly the central and darkest of all works on demonology. It became a mandatory code that combined ancient legends about black magic with the Church’s dogma of heresy, opening the gates to the torrent of inquisitorial hysteria as widely as a printed work could possibly do.