 John Paul II said in "Familiaris consortio",

Thus the innate language that expresses the total reciprocal self-giving of husband and wife is overlaid, through contraception, by an objectively contradictory language, namely, that of not giving oneself totally to the other.This leads not only to a positive refusal to be open to life but also to a falsification of the inner truth of conjugal love, which is called upon to give itself in personal totality... the difference, both anthropological and moral, between contraception and recourse to the rhythm of the cycle ..