Embryos and Fetuses, Philosophy and ?

Lisa, I am intrigued by what you are suggesting - "perhaps ...our strongest arguments are not philosophical ones."  What alternative source of reasoning do you suggest?

Steve, you are right, every claimed starting point is open to challenge, including mine.  To be clear, my position is that every human organism, at whatever stage of development, is entitled to full worth and dignity by the fact that it is a human organism.  In other words, my position is inclusive, not making distinctions that would exclude some but not all human organisms from being worthy of the state's protection.  As I said earlier, history is full of justifications for treating some human organisms as less than worthy than others (slavery, treatment of Jews, etc).  History has shown that we should be skeptical of any line drawing among human organisms because such lines have proven attempts by the powerful to take advantage of the less powerful.

But, even if my reasoning (borrowed from many others) is sound, we are still left with Steve's pressing question:  "why [do] so many people have contrary intuitions" and how does the Church employ its prophetic voice to engage them?