Except that Christianity has held throughout most sects that it is valid to kill in war. That it is valid to execute criminals. Therefore, Christianity does not have a strong case to make that it is correct conduct not to kill under any circumstances. So, the key phrase must then be "innocent human beings", and while some "pro-choicers" (happy to slice and dice baby killers) will be likely concede a fetus is "innocent" (others will wander off into moral relativism), they will not concede that the fetus is a "human being". Thus they deny the "minor premise".
And Peter agrees with this: "So the soft pro-choicer must distinguish between human beings and persons, must say that fetuses are human but not persons, and say that all persons, but not all humans, are sacred and inviolable. "
However, he tries to defeat their position by saying: "Are there any human beings who are not persons?...Are there any humans who are not persons? "
The problem is, he does not clearly define what he means by human in such a way that his opponents agree with him. This is one reason this issue has existed for 30 years - no one wants to debate the base terms - what does it mean to be human? He does clearly identify 7 "pro-choice" arguments, which he asserts they ("pro-choicers") claim are true about the weakness of pro-life arguments, and denies them all because of what he calls the invalidity of: "Functionalism: defining a person by his or her functioning or behavior."
He makes some excellant arguments against the weakness of Functionalism (and is recapitulating basic arguments made by the Buddhist philosophy quite a long time ago.) He goes on to make some excellent intellectual points (although his refutation of the 2nd argument is flawed). He refutes (or thinks he refutes) all 7 "pro-choice" pro-choice arguments, and then goes on to establish his position:
Either the fetus is a person, or not; and either we know what it is, or not. Thus there are four and only four possibilities:
1. that it is not a person and we know that,
2. that it is a person and we know that,
3. that it is a person but we do not know that, and
4. that it is not a person and we do not know that.
He then asserts that: "In case (1), abortion is perfectly permissible. We do no wrong if we kill what is not a person and we know it is not a person-e.g., if we fry a fish. But no one has ever proved with certainty that a fetus is not a person. If there exists anywhere such a proof, please show it to me and I shall convert to pro-choice on the spot if I cannot refute it. If we do not have case (1) we have either (2) or (3) or (4). What is abortion in each of these cases? It is either murder, or manslaughter, or criminal negligence.
He goes on to show how in cases 2 - 4 that abortion is wrong, and then wraps up his case without disproving case 1!!!!
And this IS the crux of the problem. Unless case 1 can be proved, the "pro-choicers" will merely assert it! He says, well, case 1 is not proved so he won't accept it. The pro-choicers say - DISPROVE IT!. And he doesn't.
Unfortunately, after all his well reasoned argument, he craps out on the 1 yard line.