Below is a response I received from an NFP professional when the subject of sexual stimulation came up outside of the ācompletionā of the marital act:
*In the second volume of āContemporary Moral Theology: Marriage Questionsā (Westminster, MD: Newman, 1963), Jesuit Fathers John C. Ford and Gerald Kelly discuss both of the situations you mention. (See pp. 213-220.) This text is still considered by orthodox moral theologians to be the definitive analysis of the subject. The case wherein the man does not climax but his wife does is treated on page 215. The act is traditionally known as āKareezaā and described thusly:
āIt is to be distinguished: from coitus interruptus, in which the man withdraws before the completion of the act and finishes it outside; from so-called āKareeza,ā in which the woman experiences orgasm but the man has no orgasm either before, during or after the act; and from those exceptional cases in which the man experiences orgasm without any ejaculation or at least without any external ejaculation [physiologically it is possible for the semen to be redirected into the bladderāK.B.]. In all of these latter three cases orgasm takes place without any true marriage act, and accordingly these practices are objectively grave sins.ā
The case in which both husband and wife do not climax is called āamplexus reservatus,ā and treated at length. Their opinion, which Fr. Hogan shares, is that āThe incomplete conjugal act [amplexus reservatus] does not involve in itself grave malice (the common and morally certain opinion), and it does not even involve [in itself] any venial malice (the common and solidly probably opinion today)ā (citing Fr. Jules Paquin, S.J.). Ford and Kelly add to this opinion the following admonition:
āThe confessor, then, should ordinarily deter penitents from this practice because of the moral dangers it involves and because his aim is to lead all his penitents, according to their capacity, not only to avoid sin, but to live lives of Christian self-restraint, self-discipline and mortification. Excessive sensual gratification brings on spiritual deterioration. But he should not accuse of mortal sin except where there is clear mortal sin. In a particular concrete case, probably a rare occurrence, it is possible that the practice could be legitimate in its object, end and circumstances. When this occurs the confessor cannot object to it even as venially sinfulā (page 220).
Note, the consideration of the husband engaging in this act āwith the full intention not to reach climax at all,ā is not something that can be morally qualified, since it is neither here nor there. It is also an pretty elusive ambition, a case of, āGood luck, fella. Confessionās at 5 oāclock at Sacred Heart on Saturdays.ā But, really, who knows what the intentions of the spouses truly are in the internal forum? Perhaps they just want to see if the thing can be done, after having read some screwy theologian in propose it in āU.S. Catholic.ā
The Vatican admonition of June 30, 1952, by Pope Pius XII, of which you may be familiar, advised bishops to quell the increasing chorus of publicists, particularly in Belgium, who were urging couples to practice āamplexus reservatusā in order to skirt the Churchās teaching on birth control. The reason for the admonition was not, however, because of the grave immorality of a successful act being performed, but because so few (approximately one-third) of couples could actually manage its performance without failure, in which case they would have engaged in an objectively grave sin. He was not ruling that the act was an objective sin, but that spiritual directors who recommended it were not dissimilar to someone who knowingly gave street directions to an alcoholic that insensitively passed through the red-light district of town.
In my opinion, anytime someone is contemplating a morally neutral act that has a 2:1 chance of failing and resulting in a grave offense to God, he should think twice or risk ātempting Godā to save him. This would amount to at least a venial sin against the theological virtue of Hope.*