that what we swear be true,
and that there be a sufficient cause for taking an oath.

350 Q. What is a vow?
A. A vow is a deliberate promise made to God to do something that is
pleasing to Him.

"Deliberate"--that is, with full consent and freedom. If we are forced
to make it, it is not valid. "To God," not to another; though we may vow
to God that we will do something in honor of the Blessed Virgin, or of
the saints, or for another. "Something pleasing," because if we promise
something that is forbidden by God or displeasing to Him, it is not a
vow. A solemn promise, for instance, to kill your neighbor or steal his
goods could not be a vow. You would commit a sin by making such a vow,
and another by keeping it, for if you promise something you cannot do
without committing sin then you must not keep that promise. We have an
example in the life of St. John the Baptist. King Herod was leading a
sinful life, and St. John rebuked him for it. The wife of the king's
brother--Herodias was her name--hated St. John for this, and she sought
to have him killed. Once when the king had a great feast and all his
notables were assembled, this woman's daughter danced before them, and
the king was so pleased with her that he vowed to give her whatever she
asked. He should have said, if it is something pleasing to God, but he
did not. Her mother made her ask for the head of John the Baptist. The
king was sad, but because he had made the vow or promise he thought he
had to keep it, and ordered St. John to be beheaded and his head brought
to her. (Matt. 14). He was not bound to keep any such vow, and sinned by
doing so.

Again, they also commit sin who become members of such secret societies
as the freemasons or similar organizations, promising to do whatever
they are ordered without knowing what may be ordered; for they sin not
only by obeying sinful commands, but by the very fact of being in a
society in which they are exposed to the danger of being forced to sin.
Such secret societies are forbidden by the Church because they strive to
undermine its authority, and make their rules superior to its teaching.
They also influence those in authority to persecute the Church and its
ministers, and do not hesitate to recommend even assassination at times
for the accomplishment of their ends. Therefore the Church forbids
Catholics to join societies of which (1) the objects are unlawful, (2)
where the means used are sinful, or (3) where the rig