Opposition to God, who is an invisible Spirit, to a certain degree originates in the very fact of the radical difference of the world from God, that is to say in the world's "visibility" and "materiality" in contrast to him who is "invisible" and "absolute Spirit"; from the world's essential and inevitable imperfection in contrast to him, the perfect being. But this opposition becomes conflict and rebellion on the ethical plane by reason of that sin which takes possession of the human heart, wherein "the desires of the flesh are against the Spirit and the desires of the Spirit are against the flesh." Concerning this sin, the Holy Spirit must "convince the world," as we have already said. Unfortunately, the resistance to the Holy Spirit which St. Paul emphasizes in the interior and subjective dimension as tension, struggle and rebellion taking place in the human heart, finds in every period of history and especially in the modern era its external dimension, which takes concrete form as the content of culture and civilization, as a philosophical system, an ideology, a program for action and for the shaping of human behavior. It reaches its clearest expression in materialism, both in its theoretical form: as a system of thought, and in its practical form: as a method of interpreting and evaluating facts, and likewise as a program of corresponding conduct. The system which has developed most and carried to its extreme practical consequences this form of thought, ideology and praxis is dialectical and historical materialism, which is still recognized as the essential core of Marxism. (Papal Encyclical, Dominum et Vivificantem, 18 May 1986).
"Disobedience" means precisely going beyond that limit, which remains impassable to the will and the freedom of man as a created being. For God the Creator is the one definitive source of the moral order in the world created by him. Man cannot decide by himself what is good and what is evil-cannot "know good and evil, like God." In the created world God indeed remains the first and sovereign source for deciding about good and evil, through the intimate truth of being, which is the reflection of the Word, the eternal Son, consubstantial with the Father. To man, created to the image of God, the Holy Spirit gives the gift of conscience, so that in this conscience the image may faithfully reflect its model, which is both Wisdom and eternal Law, the source of the moral order in man and in the world. "Disobedience," as the original dimension of sin, means the rejection of this source, through man's claim to become an independent and exclusive source for deciding about good and evil The Spirit who "searches the depths of God," and who at the same time is for man the light of conscience and the source of the moral order, knows in all its fullness this dimension of the sin inscribed in the mystery of man's beginning. Man's disobedience, nevertheless, always means a turning away from God, and in a certain sense the closing up of human freedom in his regard. It also means a certain opening of this freedom-of the human mind and will-to the one who is the "father of lies." This act of conscious choice is not only "disobedience" but also involves a certain consent to the motivation which was contained in the first temptation to sin and which is unceasingly renewed during the whole history of man on earth: "For God knows that when you eat of it your eyes will be opened, and you will be like God, knowing good and evil." (Papal Encyclical, Dominum et Vivificantem, 18 May 1986).