Pretty much, to commit a mortal sin, one must be positively SURE and positively BELIEVE that what he is doing is mortally wrong, and he must positively KNOW that he is committing a mortal sin. And then basically say, I positively KNOW this act is a mortal sin, but I don’t care, so I am going to do it anyway. If he believes that what he is doing is NOT mortally sinful, or if he is not SURE whether or not it is mortally sinful, then NO mortal sin can be committed.
The Catholic Church says that if you are unsure of whether or not you have committed a mortal sin, YOU DEFINITELY HAVE NOT COMMITTED A MORTAL SIN. Mortal sins leave no room for uncertainty and must be deliberate. The Catholic Church defines such uncertain acts as ‘Doubtful Sins’, and the Church does not require them to be confessed, since they are not Mortal Sins.
Masturbation
Overcoming the Masturbation Habit
couragerc.net/PIPMasturbation.html
Morality of Masturbatory Activity
Father Farraher also points out that sexual stimulation by a married couple is morally licit if it leads to natural vaginal intercourse or completes the marital act.'2 Farraher is very exact about what constitutes grave malice in masturbation when he writes: "for a person to be formally guilty of a mortal sin of masturbation his act must be a fully deliberate choice of what he fully realizes is seriously sinful."13 If such an act is done with only partial realization, or partial consent of the will, it is a venial sin; and “if there is no free choice of the will there is no guilt of sin at all even if the person is aware of what he is doing.”'4 Farraher goes on to point out that there is no sin even when a person foresees that sexual stimulation and orgasm will result from some action that the person is freely performing, provided that he does not intend such stimulation, but merely permits it, and that he has a sufficiently good reason for doing it. (This is simply an application of the principle of the twofold effect.)'5
Farraher corrects the misunderstanding that many Catholics have that if they experience sexual stimulation, however unwillingly, they have committed mortal sin.16
Distinction between Past Behavior and the Present
There is a little freedom, but hardly sufficient to constitute serious guilt. This is even more true when persons struggle against this impulse when they are trying to sleep at night, or are surprised by temptation in the middle of the night or upon awakening. Farraher comments at length on these situations in which the individual who has resisted the temptation to masturbate during waking hours is sometimes overwhelmed with sexual fantasies as he tries to go to sleep, or upon awakening in the morning. As long as the person makes a real effort to turn his mind away, he commits no sin even if orgasm occurs. If he is uncertain whether he really tried hard enough to get rid of fantasy, he may settle the doubt in favor of his innocence. According to traditional norms of moral theology one may presume that his intention during waking hours was also present in the moment of nocturnal temptation. Confessors and spiritual guides should reassure guilt-ridden persons who feel that since they were awake at the time of orgasm they are guilty of sin that they have not sinned inasmuch as the masturbation is presumed to be involuntary. "To tell him that he can avoid even these involuntary experiences if he tries hard enough and uses supernatural means can cause severe anxiety and even despair since he may not be able to avoid what is really involuntary."31
Guilt and Shame in All Forms of Masturbation
So, likewise, in the question of masturbation many persons torture themselves needlessly. I refer primarily to good living people whose only “sin” is masturbation. The spiritual counselor or confessor who knows the struggles that these persons have had tries to make it clear that there has been no free consent to the impulse to masturbate.
There is no grievous sin if a person masturbates while lacking in awareness, as when he is half awake, or half asleep, or when a person is carried away by sudden passion and finds himself committing the act despite the resistance of the will. This is one of the effects of original sin, that human passions tend to overcome the acts of the will (Rom. 7: l~2O). An individual may agree with this reasoning, and yet in his heart feel guilty of masturbation, because he will say to himself, “If I had tried harder I would not have had the fantasies, I should be able to get rid of all my impure thoughts.”
The trouble with this feeling of guilt is that it presupposes that we humans have perfect control over our passions not only over lust, but also over avarice, anger, and other disordered emotions. We know that we have no such control. The person involved in masturbation, however, needs to believe that with God’s grace he can overcome the habit of masturbation.
From JAW642 on 12/07/2010