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. _______________________
THIRD ARTICLE [II-II, Q. 5, Art. 3]
Whether a Man Who Disbelieves One Article of Faith, Can Have Lifeless
Faith in the Other Articles?
Objection 1: It would seem that a heretic who disbelieves one article of faith, can have lifeless faith in the other articles. For the natural intellect of a heretic is not more able than that of a catholic. Now a catholic's intellect needs the aid of the gift of faith in order to believe any article whatever of faith. Therefore it seems that heretics cannot believe any articles of faith without the gift of lifeless faith.
Obj. 2: Further, just as faith contains many articles, so does one science, viz. geometry, contain many conclusions. Now a man may possess the science of geometry as to some geometrical conclusions, and yet be ignorant of other conclusions. Therefore a man can believe some articles of faith without believing the others.
Obj. 3: Further, just as man obeys God in believing the articles of faith, so does he also in keeping the commandments of the Law. Now a man can obey some commandments, and disobey others. Therefore he can believe some articles, and disbelieve others.
On the contrary, Just as mortal sin is contrary to charity, so is disbelief in one article of faith contrary to faith. Now charity does not remain in a man after one mortal sin. Therefore neither does faith, after a man disbelieves one article.