LETTER : The human 'whole' begins at fertilization

From Fr David A. Jones, OP and

Dr Pita Enriquez Harris

Sir: It is nave to think that Catholic teaching on such matters as embryo experimentation is wrong, because it is based on ignorance of biology. Those who consider and formulate the teaching are themselves informed by many physicians and embryologists. They are not ignorant of biology.

John Habgood says (20 April) that in biology "one thing merges into another" and that biological change is always "gradual". Yet it remains that you are a genetically distinct biological individual from your mother - and were so even in the womb. The development of an embryo is gradual and continuous but fertilisation represents in some sense a discontinuity in that it signals the creation of a new biological entity.

Dr Habgood suggests that there might not even be a "mere probability" that a human embryo is a human being. Perhaps here he refers to those rare tumours which can arise from genetically doomed fertilised eggs. Such structures are not human simply by virtue of the fact that at no point did they possess the necessary genetic instructions to continue on this developmental path. Or perhaps he refers to miscarried foetuses. One might as well argue that someone who dies in childhood is a different species from someone who becomes an adult.

It is true that some of the cells in the embryo develop into the placenta and other structures, but these are still structures of the developing embryo (organs we need only in the womb).

The real disagreements here are not about facts, but interpretation, not about science but philosophy.

Yours sincerely,

DAVID A. JONES

(Blackfriars,

Oxford)

PITA ENRIQUEZ HARRIS

(Department of Biochemistry

University of Oxford)

Oxford

21 April