The discussion furthered by Bob Denahy (September AD2000) of the "infusion of a rational soul" cites St Thomas as an authority. The notion of the "infusion of a soul" into "organised matter" presupposes a dualist understanding of soul and body as distinct entities. Aquinas proposed that the soul is the form of the body.
Put simply there is no living human body without a soul, because a human body could not exist as an organised entity without form. Defining a soul as Thomas defined it, the notion of infusion of a soul is thus incoherent.
That is why the Congregation for the Doctrine of the Faith (Donum Vitae 1987) was prompted to ask in relation to the human zygote, "How could a human individual not be a person?"
There can be no such thing as the infusion of a soul. The body is, at all times of the existence of the body, the physical instantiation of a soul. The soul and the body are a unity not a duality.
DR NICHOLAS TONTI-FILIPPINI
Lecturer in Biomedical Ethics