Actually this was discussed by Sam in End of Faith. He talks about how the blastocyst is only 150 cells, and it is terminated for embryonic stem cell research. Just to show how few cells that is, he is comparing that same number that is killed by scratching ones nose. Another words, 150 cells ain’t a human being and ain’t very many cells.
For the record, I’m pro-abortion. To be clear, I’m pro-the-murder-of-unwanted-fetuses. However, the problem I have with this entire discussion is where we draw the line between fetus and child. I agree; 150 cells does not make a human. But, how many cells does make a human?
I’m not sure we’ll ever get to a consensus on this, and I do have some reservations about the lines we draw concerning where we officially designate where a fetus becomes a human.