Question 125. Fear

1. Is fear a sin?

A human act is a sin if it is disordered, because the good of a human act consists in order. For something to be correctly ordered the appetite (internal inclination) should be subject to reason. Reason says that some things should be avoided and some things sought after. When the appetite avoids what reason says we should not avoid, fear is disordered and sinful. On the other hand, when the appetite causes us to avoid what reason tells us to avoid, the appetite is neither disordered or sinful.

2. Is the sin of fear opposed to fortitude?

All fear arises from love. Men only fear losing something they love. Now love is not confined to any particular kind of virtue or vice: but rightly ordered love is included in every virtue, since every virtuous man loves the good of his virtue; while disordered love is included in every sin; thus the covetous man fears the loss of money, the intemperate man the loss of pleasure, and so on. But the greatest fear of all is death. This fear unrestrained is opposed to fortitude which regards death. Thus the sin of fear regarding death is said to be opposed to fortitude.

3. Is fear a mortal sin?

Fear is a sin when it is disordered (avoid what reason says shouldn't be avoided). Sometimes this disordered fear only involves the sensitive appetites (passions - tend to objects that are useful or pleasurable), without the consent of the rational appetite (will). In that case it can't be a mortal, but only a venial sin. But sometimes this disordered fear reaches to the will, and in this case this disordered fear is sometimes a mortal, sometimes a venial sin. For if a man through fear of death or any other temporary evil does what is forbidden by the Divine Law, or omits what is commanded by the Divine Law, such fear is a mortal sin: otherwise it is a venial sin.

Note: "The Catholic Church by virtue of the commission given to her by Christ is the Divinely constituted interpreter of the Divine Law of both the Old and the New Testament."
http://www.newadvent.org/cathen/09071a.htm


4. Does fear excuse from sin, or diminishes it?

As stated above, fear is sinful in when it goes against right reason. Reason judges certain evils to be avoided more than others. A sin wouldn't be committed if lesser evils (loss of money) are not avoided so that the bigger evils (death or sins) could be avoided, if done according to reason.

Thus death should be avoided more than the loss of temporal goods. For this reason a man would be excused from sin if through fear of death he promised to give something to a robber, yet he would be guilty of sin were he to give to sinners when not under fear of death, rather than to good people. On the other hand, if through fear a man were to avoid smaller evils but give in to bigger evils, he couldn't be totally be excused from sin, because that fear would be disordered. 

Evils of the soul (sins) should be feared more than evils of the body (beatings or death). And evils of the body more than evils of external things (loss of money). If one were to incur evils of the soul in order to avoid evils of the body or evils of external things, one would not be totally excused from sin. Yet one's sin would be diminished somewhat, for what is done through fear is less voluntary, because when fear takes control of a man he feels a need to do a certain thing. Thus Aristotle says that things done through fear are not only voluntary, but a mixture of voluntary and involuntary.


http://www.newadvent.org/summa/3125.htm