Commentary on the Gospel of Matthew

But we may also learn from this, that in respect of the reasonings only which we reason within ourselves, we are sometimes convicted and reproached as being of little faith. And I think that just as a man commits adultery in his heart only, though not proceeding altogether to the overt act, so he commits in his heart the rest of the things which are forbidden. As then he who has committed adultery in his heart will be punished proportionately to adultery of this kind, so also he who has done in his heart any one of the things forbidden, for example, who has stolen in his heart only, or borne false witness in his heart only, will not be punished as he who has stolen in fact, or who has completed the very act of false testimony, but only as he who has done such things in his heart.

There is also the case of the man who while he did not arrive at the evil action, came short of it in spite of his own will. For if, in addition to willing it, he has attempted it, but not carried it out, he will be punished not as one who has sinned in his heart alone but in deed. To questions of this sort one might ask, whether any one commits adultery in his heart, even if he does not do the deed of adultery, but lacks self-control in heart only. And the like also you will say concerning the rest of things which are deserving of praise.

But the passage possibly contains a plausible fallacy which must be cleared away, I think, in this manner: adultery which takes place in the heart is a less sin, than if one were also to add to it the act. But it is impossible that there can be chastity in the heart, hindering the chaste action— unless indeed one brings forward for an illustration of this the case of the virgin who according to the law was violated in solitude; for it may be granted that the heart of any one may be most pure, but that force in a matter of licentiousness has caused the corruption of the body of her who was chaste.

In truth she seems to me to be altogether chaste in secret heart, but no longer to be pure in body such as she was before the act of violence; but though she is not pure outwardly, is she therefore now also unchaste? I have said these things because of the words, “They reasoned among themselves saying, We took no loaves,” to which is added, “And Jesus perceiving it, said, O you of little faith, why reason ye among yourselves,” etc.; for it was necessary that investigation should be made in regard to the censure of things in secret and correlatively to the praise of things in secret.