Thomas Aquinas

“ Hence we cannot say that God is the cause of a deformed act, for He is not the cause of its deformity, though He is the cause of the act as such.
We may also reply that deformity denotes not only privation of a due form, but also a contrary disposition, wherefore deformity is compared to the act, as falsehood is to faith. Hence, just as the deformed act is not from God, so neither is a false faith; and as lifeless faith is from God, so too, acts that are good generically, though not quickened by charity, as is frequently the case in sinners, are from God. ”

“ I answer that, Two things are requisite for faith. First, that the things which are of faith should be proposed to man: this is necessary in order that man believe anything explicitly. The second thing requisite for faith is the assent of the believer to the things which are proposed to him. Accordingly, as regards the first of these, faith must needs be from God. Because those things which are of faith surpass human reason, hence they do not come to man's knowledge, unless God reveal them. ”

“ He who receives faith from God without charity, is healed from unbelief, not entirely (because the sin of his previous unbelief is not removed) but in part, namely, in the point of ceasing from committing such and such a sin. Thus it happens frequently that a man desists from one act of sin, through God causing him thus to desist, without desisting from another act of sin, through the instigation of his own malice. ”