Posner on Stem Cells

Richard Posner offers some thoughts on Stem Cell research over at his blog:

It is not easy to deal analytically with arguments that are based on religion or
emotion rather than on pragmatic considerations. Given the number of spontaneous
(not to mention deliberate) abortions and the fact that in vitro fertilization,
which produces excess embryos, is lawful, it is a little mysterious what exactly
is objectionable about using some of these excess embryos, which would otherwise
either be destroyed or stored indefinitely with dim prospects of ever being used
to produce more in vitro children, unless the objector opposes all
nonspontaneous abortion. And that is an opposition founded on religious belief.

I wasn't aware that half of all abortions are "spontaneous" (usually miscarriage), meaning that they occur naturally, usually before a woman even knows that she is pregnant. It's an important piece of information for the ethical debate on the subject, as well as the pragmatic part of the argument, as Posner notes.