Thomas Aquinas

===Magic and its practitioners===
Regarding magic, Thomas wrote that:
* only God can perform miracles, create and transform.<ref>''[[Summa contra gentiles]]'' 102</ref>
* angels and demons ("spiritual substances") may do wonderful things, but they are not miracles and merely use natural things as instruments.<ref>''Summa contra gentiles'' 103</ref>
* any efficacy of magicians does not come from the power of particular words, or celestial bodies, or special figures, or sympathetic magic, but by bidding (ibid., 105)
* "demons" are intellective substances which were created good and have chosen to be bad, it is these who are bid.<ref>''Summa contra gentiles'' 106–108</ref>
* if there is some transformation that could not occur in nature it is either the demon working on human imagination or arranging a fake.<ref>{{cite book |author=Thomas Aquinas |title=Summa Theologica |volume=I |chapter=Question 114, Article 4}}</ref>

A mention of witchcraft appears in the ''Summa Theologicae''<ref>{{cite book |title=Summa theologica Supplement |chapter=Question 38, Article 2 |quote=Whether a spell can be in impediment to marriage.}} Note this Supplement was written or compiled by others after Thomas's death.</ref> and concludes that the church does not treat temporary or permanent impotence attributed to a spell any differently to that of natural causes, as far as an impediment to marriage.

Under the ''[[canon Episcopi]]'', church doctrine held that witchcraft was not possible and any practitioners of sorcery were deluded and their acts an illusion. Thomas Aquinas was instrumental in developing a new doctrine that included the belief in the real power of witches.{{Disputed inline|date=August 2018}} This was a departure from the teachings of his master [[Albertus Magnus]] whose doctrine was based in the ''Episcopi''.<ref name="Burr17374">{{cite book |last=Burr |first=G. L. |title=Selected Writings |year=1943 |editor=L. O. Gibbons |place=New York |pages=173–174}} Original essay (1890) available here [https://play.google.com/store/books/details?id=6ZUlAQAAMAAJ] {{Webarchive|url=https://web.archive.org/web/20210225085817/https://play.google.com/store/books/details?id=6ZUlAQAAMAAJ|date=25 February 2021}}.</ref> The famous 15th-century witch-hunter's manual, the ''[[Malleus Maleficarum]]'', also written by a member of the Dominican Order, begins by quoting Thomas Aquinas ("Commentary on Pronouncements" Sent.4.34.I.Co.) refuting{{Disputed inline|date=August 2018}} the ''Episcopi'' and goes on to cite Thomas Aquinas over a hundred times.<ref>{{cite book |last=Kramer |first=Heinrich |title=Malleus Maleficarum |year=2009 |place=Cambridge |pages=91–92 |translator=Christopher Mackay}}</ref> Promoters of the witch hunts that followed often quoted Thomas more than any other source.<ref name="Burr17374" />