The moral wrongness depends on intent.Intent depends on knowledge. Acting without knowledge is negligent (immoral)Killing an innocent person is morally wrong. We are uncertain of when "personhood" begins.Abortion requires acting without knowledge.Abortion requires negligence possibly resulting in killing an innocent person.Abortion is immoral. Now, I am sure there are ways to clean this argument up, but from an apologetic perspective, here is how one would present the argument... Pro-Lifer: How certain, on a scale of 0 to 100, are you that an unborn child at 9 months gestation (days before birth) doesn't have a right to life and we can abort it? Interlocutor: 0%, of course we shouldn't abort at that point. Pro-lifer: What about 8 months, when the unborn child is still wholly viable? Interlocutor: ???% (variable based on
the interlocutor) Pro-lifer: What about 6 months.... ~ Eventually we get to the first trimester and inevitably the person might say they are 99.99% certain that the unborn child is not a person and therefor has no right to life. Pro-lifer: Ok, well, 99.99% is 1 in 10000. Imagine if I told you right now you have two choices. One, you will magically become pregnant and be forced to carry the baby to term or, two, you can take this gun and shoot it into a crowd, knowing that there is a 1 in 10,000 chance you will murder someone. Would you pull the trigger? In my experience, almost no one has supported pulling the trigger. Ultimately, many people are confused and uncertain about abortion and that confusion and uncertainty may be sufficient on its own to avoid abortion.