I was amazed to read that Father Norman Ford in his book The Prenatal Person promotes the idea that human beings in their early embryonic stage are only "potential persons."
That view does not appear to be consistent with Catholic teaching.
In a mistaken belief that one can reduce the person to subjectivity, certain Catholic personalists following Scheler and other phenomenologists and existentialists believe that our existence as persons begins with the beginning of subjectivity - and an unborn baby has little or no subjectivity.
However, other phenomenologists, including our present Pope, make the fundamental existential distinction between ontological personal selfhood and the selfhood lived through in self-presence and in other forms of subjectivity. The "substantial being" - to use a Thomist expression - exists in advance of any self-presence or other form of subjective life.
To use simpler language, we could say that the "self" we had when we were first conceived is the very same "self" we have now. We are simply at a different stage of growth. It does not depend on our ability to actualise our consciousness of self. In other words, my personal being was already embodied in the embryo long before the awakening of personal subjectivity and consciousness.
Chambers Flat, Qld