Reply Obj. 1: Some are unable to confirm their own assertions on account of their own defect: and some there are whose words should be so certain that they need no confirmation.
Reply Obj. 2: The greater the thing sworn by, the holier and the more binding is the oath, considered in itself, as Augustine states (Ad Public., Ep. xlvii): and accordingly it is a graver matter to swear by God than the Gospels. Yet the contrary may be the case on account of the manner of swearing for instance, an oath by the Gospels might be taken with deliberation and solemnity, and an oath by God frivolously and without deliberation.
Reply Obj. 3: Nothing prevents the same thing from arising out of contrary causes, by way of superabundance and defect. It is in this way that some are debarred from swearing, through being of so great authority that it is unbecoming for them to swear; while others are of such little authority that their oaths have no standing.
Reply Obj. 4: The angel's oath is adduced not on account of any defect in the angel, as though one ought not to credit his mere word, but in order to show that the statement made issues from God's infallible disposition. Thus too God is sometimes spoken of by Scripture as swearing, in order to express the immutability of His word, as the Apostle declares (Heb. 6:17). _______________________
QUESTION 90
OF THE TAKING OF GOD'S NAME BY WAY OF ADJURATION
(In Three Articles)
We must now consider the taking of God's name by way of adjuration: under which head there are three points of inquiry:
(1) Whether it is lawful to adjure a man?
(2) Whether it is lawful to adjure the demons?
(3) Whether it is lawful to adjure irrational creatures? _______________________