Whether It Is Lawful to Swear by Creatures?
Objection 1: It would seem that it is not lawful to swear by
creatures. It is written (Matt. 5:34-36): "I say to you not to swear
at all, neither by heaven . . . nor by the earth . . . nor by
Jerusalem . . . nor by thy head": and Jerome, expounding these words,
says: "Observe that the Saviour does not forbid swearing by God, but
by heaven and earth," etc.
Obj. 2: Further, punishment is not due save for a fault. Now a
punishment is appointed for one who swears by creatures: for it is
written (22, qu. i, can. Clericum): "If a cleric swears by creatures
he must be very severely rebuked: and if he shall persist in this
vicious habit we wish that he be excommunicated." Therefore it is
unlawful to swear by creatures.
Obj. 3: Further, an oath is an act of religion, as stated above (A.
4). But religious worship is not due to any creature, according to
Rom. 1:23, 25. Therefore it is not lawful to swear by a creature.
_On the contrary,_ Joseph swore "by the health of Pharaoh" (Gen.
42:16). Moreover it is customary to swear by the Gospel, by relics,
and by the saints.
_I answer that,_ As stated above (A. 1, ad 3), there are two kinds of
oath. One is uttered as a simple contestation or calling God as
witness: and this kind of oath, like faith, is based on God's truth.
Now faith is essentially and chiefly about God Who is the very truth,
and secondarily about creatures in which God's truth is reflected, as
stated above (Q. 1, A. 1). In like manner an oath is chiefly referred
to God Whose testimony is invoked; and secondarily an appeal by oath
is made to certain creatures considered, not in themselves, but as
reflecting the Divine truth. Thus we swear by the Gospel, i.e. by God
Whose truth is made known in the Gospel; and by the saints who
believed this truth and kept it.
The other way of swearing is by cursing and in this kind of oath a
creature is adduced that the judgment of God may be wrought therein.
Thus a man is wont to swear by his head, or by his son, or by some
other thing that he loves, even as the Apostle swore (2 Cor. 1:23),
saying: "I call God to witness upon my soul."
As to Joseph's oath by the health of Pharaoh this may be understood
in both ways: either by way of a curse, as though he pledged Pharao's
health to God; or by way of contestation, as though he appealed to
the truth of God's justice which the princes of the earth are
appointed to execute.
Reply Obj. 1: Our Lord forbade us to swear by creatures so as to give
them the reverence due to God. Hence Jerome adds that "the Jews,
through swearing by the angels and the like, worshipped creatures
with a Divine honor."
In the same sense a cleric is punished, according to the canons (22,
qu. i, can. Clericum, Obj. 2), for swearing by a creature, for this
savors of the blasphemy of unbelief. Hence in the next chapter, it is
said: "If any one swears by God's hair or head, or otherwise utter
blasphemy against God, and he be in ecclesiastical orders, let him be
degraded."
This suffices for the Reply to the Second Objection.
Reply Obj. 3: Religious worship is shown to one whose testimony is
invoked by oath: hence the prohibition (Ex. 23:13): "By the name of
strange gods you shall not swear." But religious worship is not given
to creatures employed in an oath in the ways mentioned above.
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