Sir

I fully support your editorial “The meaning of life” (Nature 412, 255; 2001), in which you argue that individual life does not begin with fertilization of the egg and that it thus should not be used as an argument against creating embryonic stem cells, which requires the destruction of fertilized embryos. Hubert Markl's Commentary “Research doesn't denigrate humanity” (Nature 412, 479–480; 2001) makes a similar point.

However, I regret that you missed the opportunity to point out that human reproduction by in vitro fertilization (IVF) also involves the fertilization of the egg and the early development of the embryo, and that large numbers of such embryos are destroyed.

There is thus no ethical difference between IVF and creating embryonic stem cells, as both require the creation and destruction of embryos. One can be, for religious reasons, against both, but not rationally against one and not the other. IVF has been of enormous value and so too will stem cells.