Reply Obj. 2: Faith, which is a gift of grace, inclines man to believe, by giving him a certain affection for the good, even when that faith is lifeless. Consequently the faith which the demons have, is not a gift of grace.
 Thomas Aquinas, Summa Theologica (1274). copy citation

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Author Thomas Aquinas
Source Summa Theologica
Topic faith affection
Date 1274
Language English
Reference
Note Translated by Fathers of the English Dominican Province
Weblink http://www.gutenberg.org/cache/epub/18755/pg18755-images.html

Context

“Accordingly we must say that faith is commended in the first sense in the faithful of Christ: and in this way faith is not in the demons, but only in the second way, for they see many evident signs, whereby they recognize that the teaching of the Church is from God, although they do not see the things themselves that the Church teaches, for instance that there are three Persons in God, and so forth.
Reply Obj. 1: The demons are, in a way, compelled to believe, by the evidence of signs, and so their will deserves no praise for their belief.
Reply Obj. 2: Faith, which is a gift of grace, inclines man to believe, by giving him a certain affection for the good, even when that faith is lifeless. Consequently the faith which the demons have, is not a gift of grace. Rather are they compelled to believe through their natural intellectual acumen.
Reply Obj. 3: The very fact that the signs of faith are so evident, that the demons are compelled to believe, is displeasing to them, so that their malice is by no means diminished by their belief.” source