Therefore dissimulation is not a sin. But to sin openly is always a sin. Therefore dissimulation is always a sin. Now outward signs are not only words, but also deeds. Accordingly just as it is contrary to truth to signify by words something different from that which is in one's mind, so also is it contrary to truth to employ signs of deeds or things to signify the contrary of what is in oneself, and this is what is properly denoted by dissimulation.
Consequently dissimulation is properly a lie told by the signs of outward deeds.
When, however, our pretense refers to some signification, there is no lie, but a representation of the truth. Abraham also spoke figuratively. It is evident therefore that neither dissembled. David's change of countenance was a figurative pretense, as a gloss observes in commenting on the title of Ps. And yet he is praised withal and received an earthly reward from God, not for his dissimulation, but for his zeal in destroying the worship of Baal.