I was very interested in the article by Fr Angelo Serra SJ titled "Human life: precious from conception" (February AD2000). He showed scientifically that we are human beings from the moment of conception.
However, many pro-abortionists would agree with this proposition, yet they would still deny personhood to these very small human beings.
The problem is that they believe one can reduce the person to subjectivity. They believe our existence as persons having precious value only begins with the beginning of subjectivity - although they run into great problems here themselves as they posit all sorts of criteria for personhood, e.g., quality of life, consciousness, ability to perceive and feel, etc. Some even would say that the new born baby is not yet a person and can be validly killed.
In fact it is a philosophical and spiritual problem.
Phenomenologically they fail to make the fundamental existential distinction between ontological existential personhood and selfhood lived through in self-presence or in other forms of subjectivity.
We have a substantial being (which provides us with our personhood) and this substantial being exists in advance of any self-presence or other form of subjective life such as the ability to perceive or feel.
No human being can be reduced by referring to a life "not worthy of living" as was said by some doctors during the Nazi era in Germany.
Chambers Flat, Qld