Madam, - Patsy McGarry declares (Rite and Reason, October 9th) that St Thomas Aquinas's argument that ensoulment, and therefore full humanity, does not occur for many weeks after conception is more compatible with science than the current teaching of the Catholic Church - that human life begins at conception. Mr McGarry doesn't seem fully to appreciate what science has revealed.
There is no doubt scientifically that human life begins at conception when the sperm and the egg unite to form the zygote. Thereafter, human life proceeds along a continuum until it ends in death. All of the genetic information that specifies human development is present in the zygote. No new genetic information is added later. Each stage of human life along the continuum has its own properties both peculiar and appropriate to its stage.
To pick any point on the continuum of human life, other than the starting point of conception, as marking the beginning of full human life is illogical, arbitrary, and incoherent.
St Thomas Aquinas didn't know the biology of conception and development. I have no doubt that, if he had known, he would have taught that human life began at conception. - Yours, etc,
Prof WILLIAM REVILLE, Department of Biochemistry, University College Cork.