Statement 7: In the course of history, the Fathers of the Church, her Pastors and her Doctors have taught the same doctrine - the various opinions on the infusion of the spiritual soul did not introduce any doubt about the illicitness of abortion. It is true that in the Middle Ages, when the opinion was generally held that the spiritual soul was not present until after the first few weeks, a distinction was made in the evaluation of the sin and the gravity of penal sanctions. Excellent authors allowed for this first period more lenient case solutions which they rejected for following periods. But it was never denied at that time that procured abortion, even during the first days, was objectively grave fault. This condemnation was in fact unanimous.
...and Statement 13: "Moreover, it is not up to biological sciences to make a definitive judgment on questions which are properly philosophical and moral such as the moment when a human person is constituted or the legitimacy of abortion. From a moral point of view this is certain: even if a doubt existed concerning whether the fruit of conception is already a human person, it is objectively a grave sin to dare to risk murder. "'The one who will be a man is already one.'"
Endnote 20: Tertullian, "Apologeticum" (IX. 8 PL. 1, 371-372: Corp. Christ. 1, p. 103, 1, 31-36)
...and Endnote 19: " This declaration expressly leaves aside the question of the moment when the spiritual soul is infused. There is not a unanimous tradition on this point and authors are as yet in disagreement. For some it dates from the first instant; for others it could not at least precede nidation. It is not within the competence of science to decide between these views, because the existence of an immortal soul is not a question in its field. It is a philosophical problem from which our moral affirmation remains independent for two reasons: (1) supposing a belated animation, there is still nothing less than a human life, preparing for and calling for a soul in which the nature received from parents is completed, (2) on the other hand, it suffices that this presence of the soul be probable (and one can never prove the contrary) in order that the taking of life involve accepting the risk of killing a man, not only waiting for, but already in possession of his soul."Pope Paul VI, in an audience granted to the Sacred Congregation for the Doctrine of the Faith on June 28, 1974, ratified this Declaration on Procured Abortion and has confirmed it and ordered it to be promulgated.