A smart conservative evangelical friend of mine pointed me toward the SLED argument for the pro-life position. Here's how a few websites state the SLED-argument
"SLED: Size, Level of development, Environment, and Degree of dependency.Although it’s true the unborn differs from a born human in these four ways, none of them is a relevant difference."
"Philosophically, there is no morally significant difference between the embryo you once were and the adult you are today. Differences of size, level of development, environment, and degree of dependency are not relevant in the way that abortion advocates need them to be."
"The unborn is less developed than a toddler, but toddlers are less developed than teenagers and adults and yet still human. Embryos and fetuses are not as developed as an adult but again what difference should this make?"
So for pro-life people who think along these lines, there are a few points that should be made.
1. Size Matters for some things
So let me point out that some people can't ride a roller coaster this high, and they don't have the right to be protected from that form of discrimination, the principle is broken. Sometimes size matters, does it matter for a fetus? It's not my job to prove it doesn't. I'm not the one stating that I know exactly when life is worthy.
2. Level of Development Matters for a lot of things
18 is a big age for level of development. A lot of rules change about how others can properly treat you. When you become a worthy life somewhere in the womb is another big age for level of development. It ought to be, you're going through several enormous breakthroughs in there. You start feeling, thinking, hearing and for my third trimester daughter right now, kicking... a lot.
As an embryo/fetus is going through these massive changes in level of development, we should expect massive changes in how it ought to be treated.
3. Some abortion is not all abortion
I agree that a life 5 seconds from birth is worthy. But I disagree that life 5 seconds after conception is worthy, and I think it's unclear 24 months into the pregnancy. Have some humility; be unsure with me.
4. Speaking of baby Rachael; grieving the loss of unworthy life does not mean that life was actually worthy
Lesson: sometimes we're grieved over what we didn't have yet.
A lot of pro-choice people lose their baby, are grieved, but are still pro-choice. Inconsistent? Not at all.
5. There's nothing Christian about being pro-life
What would your evangelical friends say if you became pro-choice? Like most tribal beliefs, it doesn't mean evangelicals figure out what's true and then reject it to retain membership in their group. It just means that when someone suggests pro-choice they think really hard and long trying to debunk it, and when someone suggests pro-life they're overly generous with the burden of proof. Intellectual discipline is a resource people can exercise more or less of depending on their incentives.
People who point to passages in the bible regarding abortion are out of their minds. Scripture does not talk about abortion, and there's nothing in there from which we can infer when life begins.
And I think that's about it.