We proceed to the first article thus:
1. It seems that fear is not an effect of faith. For an effect does not precede its cause. But fear precedes faith, since it is said in Ecclesiasticus 2:8: "Ye that fear God, believe in him." Hence fear is not an effect of faith.
2. Again, the same thing is not the cause of contrary effects. Now it was said in 12ae, Q.23, Art.2, that fear and hope are contraries, and the gloss on Matt.1:2, "Abraham begat Isaac," says that "faith begets hope." It follows that faith is not the cause of fear.
3. Again, one contrary is not the cause of another. Now the object of faith is something good, namely, the first truth. But it was said in 12ae, Q.18, Art.2, that the object of fear is something evil,  while it was also affirmed in the same passage that actions take their species from their objects. It follows that faith is not the cause of fear.
On the other hand: it is said in James 2:19: "the devils also believe, and tremble."
I answer: fear is a movement of the appetitive power, as we said in 12ae, Q.22, Art.2, and Q.42, Art.1, and the principle of all appetitive movements is some good or evil which is apprehended. The principle of fear, as of all appetitive movements, must therefore be some apprehension. Now through faith we apprehend certain evils which follow divine judgment as punishments. In this way, faith is the cause of the servile fear whereby one fears the punishment of God. But it is also the cause of the filial fear whereby one fears to be separated from God, and whereby one does not presume to make oneself equal with God, but holds him in reverence. For by faith we know that God is great and good, that the worst evil is to be separated from him, and that it is evil to wish to be equal with God. Unformed faith is the cause of servile fear. Formed faith is the cause of filial fear, since it is through charity that faith causes a man to adhere to God, and to be subject to him.
On the first point: fear of God cannot always precede faith, since we would not fear God at all if we were entirely ignorant of the rewards and punishments which he disposes, and of which we learn through faith. But if there is already faith in some of the articles of faith, such as the divine excellence, the fear of reverence follows, through which in turn a man submits his intellect to God, thereby believing in all of the divine promises. Hence the passage quoted continues "and your reward will not become void."
On the second point: the same thing can be the cause of contraries in relation to contraries, though not in relation to the same thing. Thus faith begets hope by causing us to appreciate the rewards which God bestows on the just, and begets fear by causing us to appreciate the punishments which he wills to inflict on sinners.
On the third point: the primary and formal object of faith is something good, namely, the first truth. But the material object of faith includes what is evil, for example, that it is evil not to be subject to God, or to be separated from him; and that sinners will endure the evils of divine punishment. In this way, faith can be the cause of fear.
 Cf. 22ae, Q. 19, Art. 1.