tantiate necessary matters, and such as come
under the investigation of reason; for it would seem absurd in a
scientific discussion to wish to prove one's point by an oath.

Reply Obj. 1: It is one thing to employ a Divine witness already
given, as when one adduces the authority of Holy Scripture; and
another to implore God to bear witness, as in an oath.

Reply Obj. 2: A man is said to pay his oaths to God because he
performs what he swears to do, or because, from the very fact that he
calls upon God to witness, he recognizes Him as possessing universal
knowledge and unerring truth.

Reply Obj. 3: A person is called to give witness, in order that he
may make known the truth about what is alleged. Now there are two
ways in which God makes known whether the alleged facts are true or
not. In one way He reveals the truth simply, either by inward
inspiration, or by unveiling the facts, namely, by making public what
was hitherto secret: in another way by punishing the lying witness,
and then He is at once judge and witness, since by punishing the liar
He makes known his lie. Hence oaths are of two kinds: one is a simple
contestation of God, as when a man says "God is my witness," or, "I
speak before God," or, "By God," which has the same meaning, as
Augustine states [*See argument On the contrary]; the other is by
cursing, and consists in a man binding himself or something of his to
punishment if what is alleged be not true.
_______________________

SECOND ARTICLE [II-II, Q. 89, Art. 2]

Whether It Is Lawful to Swear?

Objection 1: It would seem that it is not lawful to swear. Nothing
forbidden in the Divine Law is lawful. Now swearing is forbidden
(Matt. 5:34), "But I say to you not to swear at all"; and (James
5:12), "Above all things, my brethren, swear not." Therefore swearing
is unlawful.

Obj. 2: Further, whatever comes from an evil seems to be unlawful,
because according to Matt. 7:18, "neither can an evil tree bring
forth good fruit." Now swearing comes from an evil, for it is written
(Matt. 5:37): "But let your speech be: Yea, yea: No, no. And that
which is over and above these is of evil." Therefore swearing is
apparently unlawful.

Obj. 3: Further, to seek a sign of Divine Providence is to tempt God,
and this is altogether unlawful, according to Deut. 6:16, "Thou shalt
not tempt the Lord thy God." Now he that swears seems to seek a sign
of Divine Providence, since he asks God to bear witness, and this