He who swears without sufficient certitude, without a prudent examination of the facts of the question, through ignorance that must be imputed to his guilt, that one takes a rash oath—­a sin great or small according to the gravity of the circumstances.  It is not infrequently grievous.

Some oaths, instead of being statements, are promises, sworn promises.  That of which we call God to witness the truth is not something that is, but something that will be.  If one promises under oath, and has no intention of redeeming his pledge; or if he afterwards revokes such an intention without serious reasons, and fails to make good his sworn promise, he sins grievously, for he makes a fool and a liar of Almighty God who acts as sponsor of a false pledge.  Concerning temperance pledges, it may here be said that they are simple promises made to God, but not being sworn to, are not oaths in any sense of the word.

Then, again, to be lawful, an oath must be necessary or useful, demanded by the glory of God, our own or our neighbor’s good; and it must be possible to fulfil the promise within the given time.  Otherwise, we trifle with a sacred thing, we are guilty of taking vain and unnecessary oaths.  There can be no doubt but that this is highly offensive to God, who is thus made little of in His holy name.

This is the most frequent offense against the Second Commandment, the sin of profane swearing, the calling upon God to witness the truth of every second word we utter.  It betrays in a man a very weak sense of his own honesty when he cannot let his words stand for themselves.  It betokens a blasphemous disrespect for God Himself, represented by that name which is made a convenient tool to further every vulgar end.  It is therefore criminal and degrading, and the guilt thereby incurred cannot be palliated by the plea of habit.  A sin is none the less a sin because it is one of a great many.  Vice is criminal.  The victim of a vice can be considered less guilty only on condition of seriously combating that vice.  Failing in this, he must bear the full burden of his guilt.

Are we bound to keep our oaths?  If valid, we certainly are.  An oath is valid when the matter thereof is not forbidden or illicit.  The matter is illicit when the statement or promise we make is contrary to right.  He who binds himself under oath to do evil, not only does not sin in fulfiling his pledge, but would sin if he did redeem it.  The sin he thus commits may be mortal or venial according to the gravity of the matter of the oath.  He sinned in taking the oath; he sins more grievously in keeping it.

The binding force of an oath is also destroyed by fraud and deception.  Fear may have a kindred effect, if it renders one incapable of a human act.  Likewise a former oath may annul a subsequent oath under certain conditions.