Seems to me a person has some agency over their life. Something beyond a baby human; self awareness -> an ability to reason-> responsibility for one's actions. I think we achieve personhood slowly during early childhood. Most of us. Some sooner than others. Some never do.
Yeah but that's the thing, tv&cc, like Emily Lake pointed out in the other thread, if someone is in a coma, are they suddenly not a person?
I honestly don't get the problem.
I haven't read that thread nor this one in full. However, I will say two things.
(1) Instead of "person," consider "ship." What is a ship?
Suppose you have a wooden sail ship. Now remove its sail. Is it a ship? Remove its mast. Is it a ship? Remove all the ropes and cabins. Is it a ship? Remove each plank individually until there is but 1 left. Is it a ship? The answer is finally no and everyone will agree. But along the way from a full ship to its foundation to a plank, somewhere before the final plank it was no longer a ship.
Now, people may try to come up with rules and examine definitions to say some components or others are necessary, definitionally for it to be a ship. Perhaps it must have enough material to float, or maybe I have to have the capacity to carry a person unless it is broken or some other logical rules people will try to construct.
It may be that there is no definite answer because it is taken out of context, i.e.,
(2) Within the context of a function or discussion of BLAH, the consideration of a ship may have implicit requirements. So, for example, if the context was ticket sales, then we'd be asking "what is a ship [for the purpose of ticket sales]?" and that has those implicit requirements.
It is my belief that this is where the disagreement actually is. Consider "what is a person" is actually "what is a person in the context of ethics?" Some religious people think there is a soul, and so there's no difference between personhood theoretically and personhood in any context. If we want to talk about ethics, other people might consider self-awareness, the ability to experience suffering, or being functional as requirements to personhood in context.
So, I guess, back to point (1) above, consider a human, not a ship. Remove a bit, piece by piece. But consider the context of ethics. In an ethical context, ought it still be considered a person once it is no longer alive? How about once it is no longer alive and has no chance of ever being alive again? How about when it is dead as a doornail and some asshole stole its brain...is it a person? What about if it is hooked up to machines keeping its heart pumping,g but the brain was removed? It has no self-awareness, no chance of ever having that, perhaps no ability to suffer either...so is it a person in the context of ethics?
Let's say it is hooked up to machines and a Nazi doctor removes piece by piece until all there is left is skin kept alive. Surely, you would agree that it is not a person. So, at what point was it no longer a person? [in an ethical discussion]?