There is a school of thought amongst moral theologians according to which it is practically impossible for a man to commit mortal sin, because to do requires the equivalent of apostasy. Pope John Paul II makes It clear that this teaching is in error.
As we have just seen, reflection on the fundamental option has also led some theologians to undertake a basic revision of the traditional distinction between mortal sins and venial sins. They insist that the opposition to God’s law which causes the loss of sanctifying grace — and eternal damnation, when one dies in such a state of sin — could only be the result of an act which engages the person in his totality: in other words, an act of fundamental option. According to these theologians, mortal sin, which separates man from God, only exists in the rejection of God, carried out at a level of freedom which is neither to be identified with an act of choice nor capable of becoming the object of conscious awareness. Consequently, they go on to say, it is difficult, at least psychologically, to accept the fact that a Christian, who wishes to remain united to Jesus Christ and to his Church, could so easily and repeatedly commit mortal sins, as the “matter” itself of his actions would sometimes indicate. Likewise, it would be hard to accept that man is able, in a brief lapse of time, to sever radically the bond of communion with God and afterwards be converted to him by sincere repentance. The gravity of sin, they maintain, ought to be measured by the degree of engagement of the freedom of the person performing an act, rather than by the matter of that act.
The Post-Synodal Apostolic Exhortation Reconciliatio et Paenitentia reaffirmed the importance and permanent validity of the distinction between mortal and venial sins, in accordance with the Church’s tradition. And the 1983 Synod of Bishops, from which that Exhortation emerged, “not only reaffirmed the teaching of the Council of Trent concerning the existence and nature of mortal and venial sins, but it also recalled that mortal sin is sin whose object is grave matter and which is also committed with full knowledge and deliberate consent”.
The statement of the Council of Trent does not only consider the “grave matter” of mortal sin; it also recalls that its necessary condition is “full awareness and deliberate consent”. In any event, both in moral theology and in pastoral practice one is familiar with cases in which an act which is grave by reason of its matter does not constitute a mortal sin because of a lack of full awareness or deliberate consent on the part of the person performing it. Even so, “care will have to be taken not to reduce mortal sin to an act of ‘fundamental option’ — as is commonly said today — against God”, seen either as an explicit and formal rejection of God and neighbour or as an implicit and unconscious rejection of love. “For mortal sin exists also when a person knowingly and willingly, for whatever reason, chooses something gravely disordered. In fact, such a choice already includes contempt for the divine law, a rejection of God’s love for humanity and the whole of creation: the person turns away from God and loses charity. Consequently, the fundamental orientation can be radically changed by particular acts. Clearly, situations can occur which are very complex and obscure from a psychological viewpoint, and which influence the sinner’s subjective imputability. But from a consideration of the psychological sphere one cannot proceed to create a theological category, which is precisely what the ‘fundamental option’ is, understanding it in such a way that it objectively changes or casts doubt upon the traditional concept of mortal sin”.
The separation of fundamental option from deliberate choices of particular kinds of behaviour, disordered in themselves or in their circumstances, which would not engage that option, thus involves a denial of Catholic doctrine on mortal sin: “With the whole tradition of the Church, we call mortal sin the act by which man freely and consciously rejects God, his law, the covenant of love that God offers, preferring to turn in on himself or to some created and finite reality, something contrary to the divine will (conversio ad creaturam). This can occur in a direct and formal way, in the sins of idolatry, apostasy and atheism; or in an equivalent way, as in every act of disobedience to God’s commandments in a grave matter”. [VS §§69-70, , emphasis in original]
I have encountered this sort of error myself, in the confessional: the priest suggested that my sin (which I knew was mortal) really wasn’t as grave as that because I hadn’t intended to completely reject God Himself. As we can see above, this priest was mistaken; the Church’s constant teaching says otherwise. We dare not comfort ourselves that intrinsically evil acts aren’t mortal sins just because we think to ourselves that we still love God. Our own sins in those circumstances betray us.