The Church points out that modern science affirms the reality of human life at the earliest stages of development.
Sometimes the issue of abortion is supported by arguments that say human life does not begin at the moment of conception. Instead, it is argued that the human life in the womb is a “clump of cells” that can be destroyed.
Yet, these arguments based on the “science” of conception are simply false, and do not lend any support for abortion.
The Sacred Congregation for the Doctrine of the Faith pointed this out already in 1974, in their Declaration on Procured Abortion.
[M]odern genetic science brings valuable confirmation. It has demonstrated that, from the first instant, there is established the program of what this living being will be: a human, this individual human with his characteristic aspects already well determined. Right from fertilization is begun the adventure of a human life, and each of its capacities requires time–a rather lengthy time–to find its place and to be in a position to act. The least that can be said is that present science, in its most evolved state, does not give any substantial support to those who defend abortion.
Primitive societies could theoretically make such an argument, not knowing exactly what happens in the womb. However, modern science is clear that everything is present at the moment of conception to produce a unique human person.
Science supports protecting life
St. John Paul II pointed this out in his encyclical Evangelium Vitae, explaining that in reality science supports the case of protecting human life in the womb.
Furthermore, what is at stake is so important that, from the standpoint of moral obligation, the mere probability that a human person is involved would suffice to justify an absolutely clear prohibition of any intervention aimed at killing a human embryo. Precisely for this reason, over and above all scientific debates … the Church has always taught and continues to teach that the result of human procreation, from the first moment of its existence, must be guaranteed that unconditional respect which is morally due to the human being in his or her totality and unity as body and spirit: “The human being is to be respected and treated as a person from the moment of conception; and therefore from that same moment his rights as a person must be recognized, among which in the first place is the inviolable right of every innocent human being to life”
Last of all, the Vatican in its document stated that the topic of abortion should not be based on biology, as it falls squarely on human morality.
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 human is already one.”
The fact of the matter is that abortion is about killing another human person. Anyone who supports abortion has to come to terms with that reality and ask themselves if society should allow the deliberate killing of another human.