I think that the rational soul is present at conception and no later.
This is the Church’s teaching too no?
Before I ask my main question though, I would like to cast my hat in the ring of contenders who argue with each other over when the rational soul exists. Some say that ensoulment takes place over a period of time with the vegetative, sensitive, and rational soul following each other in succession. But I think that this is impossible, because if this was true then either the human being has multiple substantial forms which is absurd, or the human being was not a human being and is actually multiple substances which is born and dissolves with each subsequent ensoulment and this doctrine is so singular that alas, the old saying that “there is nothing so absurd that a philosopher has not taught it” fails to describe its unreason.
And again, if man has multiple souls, then how is man a single, united substance and not just an accidental unity of differing things? To claim that man has many souls is to cut at the root of what it means to be human.
So clearly there is but one soul in man, which soul can better express itself as the body grows; for first the body is weak, so only the souls nutritive powers are seen, then as the body grows stronger then the sensible and rational parts are capable of being expressed.
My main question now, is does the Church or anyone know when conception happens? If not, could we maintain that we don’t really know when a human becomes a human because we don’t know when any particular conception happens?