Study and Meditations on this Sunday's Scripture Readings: February 13, 2011

[Fidelis]

The Catholic Encyclopedia has a very helpful short article on this subject found here. Here is an excerpt:

An oath is licit, and an act of virtue, under certain conditions. It is, in effect, an act of homage rendered by the creature to the wisdom and omnipotence of the Creator—it is therefore an act of the virtue of religion; moreover, it is an excellent way of affording men security in their mutual intercourse. It is justified in the Old and New Testament; the faithful and the Church from Apostolic times to the present day have employed oaths; and canonical legislation and doctrinal decrees have affirmed their lawfulness. Improper use is often made of oaths, and the habit of swearing may easily lead to abuses and even to perjury.** In counselling men “not to swear at all” (Matthew 5:34) Christ meant, as the Fathers and ecclesiastical writers explain, to be so truthful that men could believe them without need of oath to confirm what they say. He did not forbid the use of oaths under proper conditions, when necessary to satisfy others of our truthfulness.** These conditions are (Jeremiah 4:2):

(1) Judgment, or careful and reverent consideration of the necessity or utility of the oath; for it would be showing a want of the respect due to God, to invoke Him as witness in trivial matters; on the other hand, it would be wrong to require a grave or extreme necessity. To swear without a sufficient reason, being an idle use of God’s name, is a venial sin;

(2) truth, for what we affirm should be in conformity with the truth. Consequently in case of an assertory oath, our affirmation must be truthful, and in a promissory oath we must have the intention of doing what we are promising. To swear falsely constitutes the sin of perjury, always mortal in its nature: for it is an insult to the Divine Truth to call God in witness to a lie; besides, such an act is likely to do injury to the common good; see the propositions condemned by Innocent XI, prop. xxiv;

(3) justice requiring: (a) in the case of an assertory oath, that it be lawful to make the affirmation which one wishes to corroborate; failure to observe this condition is a venial sin, as when boasting of some evil deed one should swear to it; it is a grievous sin, if one employs an oath as the means and instrument of sin, at least of mortal sin, for example, to make a person believe a grave detraction; (b) in the case of a promissory oath, justice requires that one be able to assume licitly the obligation of doing the thing promised. It is a mortal sin to promise an oath to do a grievously illicit thing; and it is, in the opinion of St. Alphonsus Liguori, a mortal sin to swear to do a thing which is illicit though not grievously so.