Pro-life writer guilty of confused reasoning

DR Gaven Kerr (Write Back, June 27) takes me to task for using the word ‘metaphysics’ and claims I am confused.

By ‘metaphysics’, I meant only considerations beyond the physical — ie those which cannot be determined by experimental investigation. Often such views are religious, or theological, but I grant him not always. Dr Kerr claims “metaphysics is simply the study of what it is to be”. No, that is ontology — a branch of metaphysics.

It seems to me that attributing personhood to a single cell is a metaphysical claim, and one that those religious people against abortion make. He says “a person is a substance of a rational nature... regardless of whether it has the use of rationality or not”. Can it be a rational substance if it is not a substance that can reason? What would that even mean?

Dr Kerr wishes to say the egg is a rational substance, therefore it is a person. This cannot be true, because if it were, then every cell of my body would also have to be considered a rational substance and so a distinct person, since a clone of me could be made from each cell and these clones would be separate, individual people.

It seems to me the single cell develops into a person as the embryo develops the properties we recognise as characteristic of people.

Perhaps that is metaphysical confusion, but it seems like sense to me.