jocose lie is not a mortal sin in perfect men, except perhaps
accidentally on account of scandal. We may take in this sense the
saying of Augustine that "it is a precept of perfection not only not
to lie at all, but not even to wish to lie": although Augustine says
this not positively but dubiously, for he begins by saying: "Unless
perhaps it is a precept," etc. Nor does it matter that they are
placed in a position to safeguard the truth: because they are bound
to safeguard the truth by virtue of their office in judging or
teaching, and if they lie in these matters their lie will be a mortal
sin: but it does not follow that they sin mortally when they lie in
other matters.
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QUESTION 111

OF DISSIMULATION AND HYPOCRISY
(In Four Articles)

In due sequence we must consider dissimulation and hypocrisy. Under
this head there are four points of inquiry:

(1) Whether all dissimulation is a sin?

(2) Whether hypocrisy is dissimulation?

(3) Whether it is opposed to truth?

(4) Whether it is a mortal sin?
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FIRST ARTICLE [II-II, Q. 111, Art. 1]

Whether All Dissimulation Is a Sin?

Objection 1: It seems that not all dissimulation is a sin. For it is
written (Luke 24:28) that our Lord "pretended [Douay: 'made as
though'] he would go farther"; and Ambrose in his book on the
Patriarchs (De Abraham i) says of Abraham that he "spoke craftily to
his servants, when he said" (Gen. 22:5): "I and the boy will go with
speed as far as yonder, and after we have worshipped, will return to
you." Now to pretend and to speak craftily savor of dissimulation:
and yet it is not to be said that there was sin in Christ or Abraham.
Therefore not all dissimulation is a sin.

Obj. 2: Further, no sin is profitable. But according to Jerome, in
his commentary on Gal. 2:11, "When Peter [Vulg.: 'Cephas'] was come
to Antioch:--The example of Jehu, king of Israel, who slew the priest
of Baal, pretending that he desired to worship idols, should teach us
that dissimulation is useful and sometimes to be employed"; and David
"changed his countenance before" Achis, king of Geth (1 Kings 21:13).
Therefore not all dissimulation is a sin.

Obj. 3: Further, good is contrary to evil. Therefore if it is evil to
simulate good, it is good to simulate evil.

Obj. 4: Further, it is written in condemnation of certain people
(Isa. 3:9): "They have proclaimed abroad their sin as Sodom, and they
have not hid it