The Catholic position has been riddled with such absurdities. A number of adjustments have been made, in an effort to preserve the view.

One problem has been that the position implies that every unfertilised ovum and every sperm are potential persons--as long as the right conditions obtain. So is the thing which consists of a sperm in one body and a ripe but unfertilised ovum in another.

The response has been to rely on the ideas that the ovum and the sperm are two things, not one; and that though both are human and alive, they are not human lives.

But that response relies on adopting criteria for counting things (which is arbitrary), and accepting the criteria for indentity of things (which is not, but which leaves them open to the objections I raised in my earlier post).

The problem that every live human cell turns out to be a potential person is met by insisting that for something to be a potential person, it must to develop into one by purely natural processes. I take it that that means, without human intervention. (That would also deal with the sperm and ovum problem--for this purpose, human intercourse is not purely natural.)

But the problem is that a zygote does not produce a child by purely natural processes (as that is defined). For the mother must eat.

Perhaps Michael Cook, you could provide a response?

I quite agree that scientific research needs to be within ethical boundaries.

The problem is that once again religion is trying to assert its dogma as the guiding ethics.

As has been shown from Gallileo onwards to contraception, religious dogma is a disfunctional moral compass that serves the church over the community.

When the world recognises that priests, bishops, mullahs etc are authorities on their religions and not morality, then maybe science can proceed ethically to produce benefits for us all unfettered by dogma.