Peter Kreeft is brilliant. He’s also very hard to keep up with – there’s so much going on in his texts. This line of reasoning – and the ‘simplifications’ that some commenters make at the end – are THE argument against abortion on demand. If you can follow them. Its well worth posting here despite being somewhat rich.
It was reposted just this week at Inside Catholic: http://insidecatholic.com/Joomla/index.php?option=com_content&task=view&id=6795&Itemid=48
One commenter simplified well when they said:
1. It is always wrong to kill an innocent human being.
2. unborn babies are human beings.
3. Abortion kills an unborn human being.
4. Therefore, abortion is wrong.
He originally published it in 2000. See: http://www.peterkreeft.com/topics-more/personhood_apple.htm
The meat of the argument is:
1. We Know What an Apple Is
2. We Really Know What an Apple Really Is
3. We Really Know What Some Things Really Are
4. We Know What Human Beings Are
5. We Have Human Rights Because We Are Human
6. Morality Is Based on Metaphysics
7. Moral Arguments Presuppose Metaphysical Principles
8. Might Making Right
9. Either All Have Rights or Only Some Have Rights
10. Why Abortion Is Wrong
11. The Argument From the Nonexistence of Nonpersons
12. Three Pro-Life Premises and Three Pro-Choice Alternatives
13. The Argument from Skepticism