The principles the Pope outlined in this bull were later embodied in the Malleus Maleficarum (“The Hammer of Witches”). Two Dominican inquisitors, Jacob Sprenger and Heinrich Kramer, compiled it and submitted the book to the University of Cologne’s Faculty of Theology for their approbation on 9 May 1487. This is usually taken as the date of publication, although earlier editions may have been produced in 1485 or 1486. The book itself was not specifically ordered by the Catholic Church but was written to lend credence to and enforce the bull. To help its credulity the writers then attached the letter of approbation from the University of Cologne, signed by four of its professors.
The Malleus was published in a number of editions, thirteen times from 1487 to 1520 and revived another sixteen times from 1574 to 1669. The book was popular throughout Europe with at least sixteen German editions, eleven French editions, two Italian editions, and several English editions; the English editions however, did not appear until much later, e.g.: 1584, 1595, 1604, 1615, 1620 and 1669. For its time, the Malleus was the lead authority available to the masses on the subject of witchcraft, and soon became accepted by both Catholics and Protestants.
The book itself is divided into three sections, the first proving that witchcraft or sorcery existed, the second describing the forms of witchcraft, and the third describing the detection, trial and destruction of witches. The first two sections are thought to have been the work of Sprenger, who as a distinguished theologian put together the theological and intellectual components of the book. Section three and the practical components of the book are most likely the work of Kramer, who had conducted a campaign in the Tirol during the early 1480s and had gain much experience as a trial judge. There is little original material in the book, being mainly a codification of existing beliefs and practices, with substantial parts taken from earlier works such as Johannes Nider’s Praeceptorium and Formicarius (1435).
Interestingly, Pope Innocent VIII died on 25 July 1492, leaving behind him numerous children (Octo Nocens pueros genuit, totidemque puellas; Hunc merito poterit dicere Roma patrem – “Eight wicked boys born, and just as many girls, so this man could be entitled to be called Father of Rome”), towards whom his nepotism had been as lavish as it was shameless.