HKB
x): "'Hypocrite' is a Greek word corresponding to the Latin 'simulator,' for whereas he is evil within," he "shows himself outwardly as being good; hypo denoting falsehood, and krisis, judgment."
I answer that, As Isidore says (Etym. x), "the word hypocrite is derived from the appearance of those who come on to the stage with a disguised face, by changing the color of their complexion, so as to imitate the complexion of the person they simulate, at one time under the guise of a man, at another under the guise of a woman, so as to deceive the people in their acting." Hence Augustine says (De Serm. Dom. ii) that "just as hypocrites by simulating other persons act the parts of those they are not (since he that acts the part of Agamemnon is not that man himself but pretends to be), so too in the Church and in every department of human life, whoever wishes to seem what he is not is a hypocrite: for he pretends to be just without being so in reality."
We must conclude, therefore, that hypocrisy is dissimulation, not, however, any form of dissimulation, but only when one person simulates another, as when a sinner simulates the person of a just man.
Reply Obj. 1: The outward deed is a natural sign of the intention. Accordingly when a man does good works pertaining by their genus to the service of God, and seeks by their means to please, not God but man, he simulates a right intention which he has not. Wherefore Gregory says (Moral.) that "hypocrites make God's interests subservient to worldly purposes, since by making a show of saintly conduct they seek, not to turn men to God, but to draw to themselves the applause of their approval:" and so they make a lying pretense of having a good intention, which they have not, although they do not pretend to do a good deed without doing it.
Reply Obj. 2: The habit of holiness, for instance the religious or the clerical habit, signifies a state whereby one is bound to perform works of perfection. And so when a man puts on the habit of holiness, with the intention of entering the state of perfection, if he fail through weakness, he is not a dissembler or a hypocrite, because he is not bound to disclose his sin by laying aside the habit of holiness. If, however, he were to put on the habit of holiness in order to make a show of righteousness, he would be a hypocrite and a dissembler.
Reply Obj. 3: In dissimulation, as in a lie, there are two things: one by way of sign, the other by way of thing signified. Accordingly the evil intention in hypocrisy is considered as a thing signified, which does not tally with the sign: and the outward words, or deeds, or any sensible objects are considered in every dissimulation and lie as a sign.
THIRD ARTICLE [II-II, Q. 111, Art. 3]
Whether Hypocrisy Is Contrary to the Virtue of Truth?
Objection 1: It seems that hypocrisy is not contrary to the virtue of truth. For in dissimulation or hypocrisy there is a sign and a thing signified. Now with regard to neither of these does it seem to be opposed to any special virtue: for a hypocrite simulates any virtue, and by means of any virtuous deeds, such as fasting, prayer and alms deeds, as stated in Matt. 6:1-18. Therefore hypocrisy is not specially opposed to the virtue of truth.
Obj. 2: Further, all dissimulation seems to proceed from guile, wherefore it is opposed to simplicity. Now guile is opposed to prudence as above stated (Q. 55, A. 4). Therefore, hypocrisy which is dissimulation is not opposed to truth, but rather to prudence or simplicity.