Jerome's Commentary on Matthew 5:28 says the following:
“Whoever looks upon a woman to lust after her has already committed adultery with her in his heart.” There is a difference between πάθος and προπάθεια, that is to say, between passion and pre-passion. Passion is regarded as a vice, but pre-passion (though it may have blame in its commencement), is not reputed as a sin. Therefore, “whoever looks upon a woman,” and his spirit becomes stimulated, has been struck by pre-passion; but if he consents and makes an affection out of the thought, then it has passed from pre-passion to passion, as is written in David: “They passed into the feeling of the heart.” [Psalm 73:7] To such a one, the will to sin is not absent, but only the opportunity. Whoever then “looks upon a woman to lust,” that is, if he looks in order to lust, so that he is disposed to act, that one rightly is said to have “committed adultery with her in his heart.”
This straightforward interpretation, following Origen and Didymus the Blind's use of Stoic psychological categories, contradicts the conclusions of some who, following Augustine's later opinions, consider all agitations of the σάρξ, including pre-cognitive stirrings of the body toward sexual arousal or anger, to be morally culpable sin. This can provide some comfort, lest we feel condemned for feeling anything at all.
In his commentary on Matthew 5:29, he tells us where our responsibility lies:
"But if your right eye is an occasion of sin to you," etc. Since he had spoken above about lust for a woman, he has now rightly named as the eye the thought and feeling that is flying about in different directions. By the right [hand] and by the other parts of the body are indicated the beginnings of the will and of feeling, so that what we conceive with the mind, we would fulfill in deed. We must beware, then, that what is best in us should not quickly slip into vice. For if the right eye and right hand are occasions for sin, how much more the things which are on the left in us. If the spirit slips, how much more the body, which is more prone toward sins. Here is another interpretation: By the right eye and right hand is shown affection for brothers, wife, children, neighbors, and close relatives. [Cf. Luke 18:29-30.] If we see them as a hindrance to us in contemplating the true light, we ought to cut off such parts, lest, while we want to gain others, we ourselves may perish forever. [Cf. 1 Cor. 9:22,27; Rom. 14:15.] This is why it is said of the high priest whose spirit was consecrated to the worship of God: "For mother and father and sons, he will not be defiled." [Leviticus 21:11] This means that he will not know any affection except for him to whose worship he has been consecrated.
Thus, even if we view propatheia as morally blameless temptations, we quickly need to make radical sacrifices to keep them from overcoming us.
