Objection 1: It would seem that no habit is infused in man by God. For God treats all equally. If therefore He infuses habits into some, He would infuse them into all: which is clearly untrue.
Obj. 2: Further, God works in all things according to the mode which is suitable to their nature: for "it belongs to Divine providence to preserve nature," as Dionysius says (Div. Nom. iv). But habits are naturally caused in man by acts, as we have said above (A. 2). Therefore God does not cause habits to be in man except by acts.
Obj. 3: Further, if any habit be infused into man by God, man can by that habit perform many acts. But "from those acts a like habit is caused" (Ethic. ii, 1, 2). Consequently there will be two habits of the same species in the same man, one acquired, the other infused. Now this seems impossible: for the two forms of the same species cannot be in the same subject. Therefore a habit is not infused into man by God.
On the contrary, it is written (Ecclus. 15:5): "God filled him with the spirit of wisdom and understanding." Now wisdom and understanding are habits. Therefore some habits are infused into man by God.
I answer that, Some habits are infused by God into man, for two reasons.
The first reason is because there are some habits by which man is disposed to an end which exceeds the proportion of human nature, namely, the ultimate and perfect happiness of man, as stated above (Q. 5, A. 5). And since habits need to be in proportion with that to which man is disposed by them, therefore is it necessary that those habits, which dispose to this end, exceed the proportion of human nature. Wherefore such habits can never be in man except by Divine infusion, as is the case with all gratuitous virtues.
The other reason is, because God can produce the effects of second causes, without these second causes, as we have said in the First Part (Q. 105, A. 6). Just as, therefore, sometimes, in order to show His power, He causes health, without its natural cause, but which nature could have caused, so also, at times, for the manifestation of His power, He infuses into man even those habits which can be caused by a natural power. Thus He gave to the apostles the science of the Scriptures and of all tongues, which men can acquire by study or by custom, but not so perfectly.
Reply Obj. 1: God, in respect of His Nature, is the same to all, but in respect of the order of His Wisdom, for some fixed motive, gives certain things to some, which He does not give to others.
Reply Obj. 2: That God works in all according to their mode, does not hinder God from doing what nature cannot do: but it follows from this that He does nothing contrary to that which is suitable to nature.
Reply Obj. 3: Acts produced by an infused habit, do not cause a habit, but strengthen the already existing habit; just as the remedies of medicine given to a man who is naturally health, do not cause a kind of health, but give new strength to the health he had before.