Part II - How relevant is our uncertainty as to the moment of our beginning?
The second rational premise is supplied by his answer, in the second paragraph of this article, to the first part of the statement at the outset of article sixty: 'Some people try to justify abortion by claiming ...'71
For he answers that 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'72.
Therefore, there are two reasons for the prohibition of procured abortion: the first is affirmation of a 'personal presence at the moment of the first appearance of a human life'; and the second is that the 'mere probability that a human person is involved would suffice ...'
Furthermore, these two reasons, taken together or separately, are a sufficient argument in themselves to make the philosophical proof of a soul's existence from conception, a proof not fundamental to determining the morality of the action of procured abortion.
For if the soul could be proved to enter the body at some point subsequent to conception, then the ordination of that beginning of conception to that moment of ensoulment would itself be sufficient reason for declaring that the objective intention of a procured abortion would still be the killing of a human being.
It is this objective intention which so fundamentally transgresses the first principle of the natural law: 'good is to be done and evil is to be avoided'73.