Spirit - that is, the human person - cannot be conceived simply by the sexual union of a man and woman. It is “the work of God Himself” ( Love and Responsibility , 55). Sex thus participates in God’s ongoing creation of persons, a creation that must, John Paul II thinks, be continuous because “the world is made up of creatures, or in other words entities which have no existence of and by themselves, since they do not themselves contain the final cause or source of their existence” (54).
Love does not in itself “give existence to a new spirit,” but it ought to motivate sexual relations. And love also comes into play in the continuing formation of the person, that is, in education: “Love owes its fertility in the biological sense to the sexual urge but it must also possess a fertility of its own in the spiritual, moral,and personal sphere. It is here that the full productive power of love between persons, man and woman, is concentrated, in the work of rearing new persons. This is its proper end, its natural orientation. Education is a creative activity with persons as the only possible object” (55-56).
Training a child into full personhood is not a purely human activity, any more than the formation of the person was: God “does not leave the work of education . . . wholly and entirely to the parents but Himself takes part in it, in His own person. For something more than the love of parents was present at the origin of a new person - they were only co-creators; the love of the Creator decided that a new person would come into existence in the mother’s womb. Grace is, so to speak, the continuation of this work. God Himself takes the supreme part in the creation of a human person in the spiritual, moral, strictly supernatural sphere” (56).