Thomas Aquinas, on 1Tim 4:2

“Speaking lies in hypocrisy, and having their conscience seared,”

“On the part of those deceived, the cause is also twofold: one is their falsity; the other is the perversity of their conscience. In regard to the first he says, of devils, i.e., of men possessed by a Devil; of devils I say, speaking lies: how long shall this be in the heart of the prophets that prophecy lies, and that prophesy the delusions of their own heart (Jer 23:36). And note that no one could deceive another with a simple lie, unless it was covered with the appearance of truth. And so, they never could succeed in deceiving unless they pretended to have a good intention, or put a cloak over their pretense or false authority: let no man deceive you with vain words (Eph 5:6); having an appearance indeed of godliness, but denying the power thereof. Now these avoid (2 Tim 3:5). And of devils, I say, having their conscience seared. Flesh is said to be seared, when it is corrupted by fire and is in such a condition that rot flows from it continuously. Thus, by means of the fire of a perverse will, of anger, of hatred, of concupiscence, the conscience is ulcerated and the false doctrine of devils continually issues from it: both their mind and their conscience are defiled (Titus 1:15).”

Imported from an open dataset — not yet checked against the printed edition.