A friend uses the “ensoulment” argument to defend early abortion. She said Aquinas taught an unborn baby doesn’t receive a soul until 40 days after conception and the Church still teaches this. Does the Church say when a person receives a soul?

While St. Thomas did subscribe to the Aristotelian 40-to-80-day “ensoulment” hypothesis that a spiritual soul was present 40 or 80 days after conception (40 days for boys and 80 days for girls), he never wavered in his belief that abortion was always gravely wrong.

Concerning the Church’s teaching on the issue of ensoulment, Pope St. John Paul’s encyclical Evangelium Vitae states:

Even if the presence of a spiritual soul cannot be ascertained by empirical data, the results themselves of scientific research on the human embryo provide a valuable indication for discerning by the use of reason a personal presence at the moment of the first appearance of a human life: How could a human individual not be a human person?(EV60).

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 and those philosophical affirmations to which the magisterium has not expressly committed itself, 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 that 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. (EV 60)