The mediaeval battlefields of thought were strewn with various forms of it.
This missile was the charge of unlawful compact with Satan, and it was most effective.

We find it used against every great investigator of nature in those times and for ages after.

The list of great men in those centuries charged with magic, as given by Naude, is astounding; it includes every man of real mark, and in the midst of them stands one of the most thoughtful popes, Sylvester II (Gerbert), and the foremost of mediaeval thinkers on natural science, Albert the Great.

It came to be the accepted idea that, as soon as a man conceived a wish to study the works of God, his first step must be a league with the devil.
It was entirely natural, then, that in 1163 Pope Alexander III, in connection with the Council of Tours, forbade the study of physics to all ecclesiastics, which, of course, in that age meant prohibition of all such scientific studies to the only persons likely to make them.
What the Pope then expressly forbade was, in the words of the papal bull, "the study of physics or the laws of the world," and it was added that any person violating this rule "shall be avoided by all and excommunicated."(274) (274) For the charge of magic against scholars and others, see Naude, Apologie pour les Grands Hommes soupconnes de Magie, passim; also Maury, Hist.

de la Magie, troisieme edition, pp.