I am frequently asked why we should use human pre-embryos for research.

One of the problems inherent in the debate about embryo experimentation is that of terminology. There is much misunderstanding about what the word ‘embryo’ actually refers to and what actually constitutes an experiment. A reasonable framework of reference is necessary to address the issues and to come to some meaningful conclusions. The word ‘pre-embryo’ was introduced by Dr Anne McLaren (a member of the British Government's Warnock Committee and of the United Kingdom Voluntary Licensing Authority) in order to eliminate confusion. It applies to the entity which exists prior to the appearance of the primitive streak at day 14. I shall use this term in the manner recommended by Dr McLaren, in order to distinguish this stage of development from the later embryo.

If you begin with the notion that you shouldn't use pre-embryos unless there is a good argument for doing so, then the reasons will always be very specific. This is essentially how scientists have to approach this type of research because a well-founded case for involving pre-embryos always has to be made to an institutional ethics committee (or even several committees, as in our own situation). In general, scientists have essentially similar views to those of the community in which they are brought up. They consider that the human pre-embryo deserves greater respect than those of other species, in fact they have the same hierarchy of values for pre-embryos of different species as the general community have for fully grown members of different species.