from a review of Klaassen's new book Transformations of Magic

"His attentiveness to the volumes ultimately sheds light on the
intellectual frames of reference that result in the transformations he
documents. Regarding image magic the framing question was whether an
image worked because of occult natural powers or demonic intervention.
In the former case, use of the image would be lawful; in the latter,
unlawful. The urge to make image magic lawful then situated it
alongside or even in the field of natural philosophy. The alignment
shaped the debate and can be seen in the placement of the texts of
image magic, which in collected volumes and on library shelves were
found among the <i>naturalia</i>. Prof. Klaassen determines that this
trend was shaped by certain authoritative works, most famously the
</i>Speculum astronomiae</i>, that became increasingly used as a guide
for scribes in their immediate discernment of the philosophical and
moral lawfulness of particular magical texts. Their use had a
constraining effect, and the number of texts of image magic
correspondingly decreased."

Klaassen, Frank F. <i>Transformations of Magic: Illicit Learned Magic
in the Later Middle Ages and Renaissance</i>. Series: Magic in History.
 University Park: Pennsylvania State University Press, 2013. Pp. x,
280. $69.95. ISBN-13: 9780271056265.

  Reviewed by David J. Collins, S.J.
       Georgetown University

The Medieval Review
https://scholarworks.iu.edu/dspace/handle/2022/3631