The article considers a certain number of answers already given to this question. It then studies in details three articles from 1961 dealing with the problem. The argumentation given up to now seems to require to be completed and, on certain points, corrected.
The article makes it clear that what was rejected by Humanae vitae as intrinsically bad is the separation, practiced in the conjugal act itself, of the unitive aspect from the procreative aspect.
The article then develops an argument largely inspired by the declarations having to do with procreation found in Donum vitae: «The tradition of the Church and anthropological reflection recognize in marriage and in its indissoluble union the only place worthy of truly responsible procreation» (DV 11, 1); «Procreation is morally deprived of its proper perfection when it is not wanted as the fruit of the conjugal action, namely the act which is specific to the union of the spouses» (DV II, 4).
To avoid procreation outside of marriage, by non-abortifacient means and according to the rules of the «principle of totality» is a moral good.