That's a good point. However, none of the examples of situations where the definition is debatable apply to humans. The page lists viruses, colonial organisms, zooids, and collaboration organisms. I think for humans (which I think is the most widely studied organism), scientists can clearly define what is an organism and what isn't.
I think if you were to survey biologists, the vast majority (95%+) would agree with me on all the cases ("is this specific thing a human organism") you listed.
>"entity" (which is an absolutely load-bearing concept in your definition which, again, you leave undefined)
Ok. Let's define it as "a cell or group of cells that are joined together and acting together".
>You argued that an unfertilized egg cannot be considered a person because it is "clearly" a different entity from the fertilized egg.
I said "I think there's a clear biological difference between an entity receiving nutrition, and 2 entities, each with half of a set of DNA, coming together to make a single entity with a full set of DNA."
My point was that there's a clear difference between receiving nutrition and 2 entities with half a set of DNA coming together. My point wasn't that the unfertilized egg and fertilized egg are clearly different entities (as you've pointed out, that's not exactly clear, and depends on the definition entity).
My definition doesn't hinge on the unfertilized egg and fertilized egg being different entities. An unfertilized egg won't typically grow into an adult human. A fertilized egg will typically grow into an adult human.
>At some point in the distant past, our ancestors were non-human (and, possibly but not necessarily at the same time, not persons). The logical conclusion from your axiom is that there was, at some point, a hard boundary where an entirely nonperson animal gave birth to a "full person" human (and that first human then presumably had to reproduce through bestiality, unless through some amazing fortune another full 100% human being was born and fertile during their fertile years).
That's a good point. One thing though is that our actions today can't impact people in the past. So from an ethics point of view, we don't need to worry about the past, only the present and future. And as you say, we don't 100% know what happened in the past.
With the partial people view, someone might conclude today a person with a certain genetic disorder is similar to an ape, and thus a partial person, and thus doesn't need rights. By saying "no partial people today", we avoid that problem.
>If you believe that it is, your opinion is consistent. If it's not, then you must at least permit abortion in the case of rape, even if the fetus is a person.
I would say the way to resolve this is by defining what is the standard care that each person deserves.
If someone needs an exotic treatment that costs $1B/day to survive each day, and a hospital has the treatment in stock, is the hospital obligated to provide it to someone who can't pay? I would say no. It's within the hospital's rights to not give the person the treatment, or cease treatment if already provided in previous days.
However, is it within the hospital's rights to cease providing the person food and water against the person's will? (Let's avoid the euthanasia discussion and say the person is fully responsive but is quadriplegic.) I would say no. Food and water are standard care, and cannot be denied.
Food and water are standard care. The $1B treatment isn't.
2 people being attached permanently for the purpose of blood processing of a failed kidney isn't standard care.
A mother's womb is standard care for a fetus.
(Another thing to consider is what direct action is taken. In a D&E abortion, the fetus is cut into pieces with a scissors, which is the cause of death. So in the specific case of a D&E abortion, there's a second clear difference from the blood treatment case, in that it's a direct physical attack on the fetus that kills the fetus. E.g. in the kidney failure case, would it be ok to cut the person into pieces with a chainsaw? No, even if the person already is going to die of kidney failure. Other types of abortion are not as direct though, so this argument can't be as clearly used to condemn all types of abortion.)