Huh? Of course it didn't. My view of the word has been and continues to be correct. Why is this so weirdly emotional and personal for you? Can't you just admit you learned something?
You're the one who brought it up and were offended that I was calling the viability concept arbitrary. People use it when they feel there are inconsistencies or little relevance in the given reasons. etc., which makes it seem as if they had more than one choice to go by hence arbitrary.
Of course how viable something is is significant. It would take a truly stupid person to view something that has a 99.9% chance of survival and a .001% chance of survival as being equivalent. Remember, we're dealing with people who aren't trying to make deliberately silly arguments like you are.
There is a BIG similarity to the conservative argument, since even at that point, they are just potential persons. This is why some people view it as arbitrary because the crucial difference is still not there. Luckily, late term abortion is not a significant problem, but the concept is just BS. What harm is there if it's killed at the viability period if it never existed as a person in the first place? And as many pro-choice people argue, there are situations where the baby would probably be better off not living as an unwanted kid. There are tons of foster kids who want to kill themselves and wish they never were born and a bunch of other issues.
This is the book stating what critics may argue, not that such an argument is compelling from a public policy perspective as it is not. It's the same as picking an age limit for entering into contracts, voting, for driving, or anything else. Is an 18 year old meaningfully different than a 17 year and 364 day old? Of course not. If you're making a time related rule however the line must be drawn somewhere, and we have chosen to place it at a time when we believe that most people will be sufficiently mature to enter into a contract or whatever.
Abortion up to birth is definitely compelling. There is no good argument against it unless you want to act like a conservative and argue they could have a future like ours. There are some however for newborns.
I know what the book is doing. It's remaining neutral on any of the positions. But I guess that's also why you think it's supportive of your view of usage of arbitrary since it put "seems" or "seemingly" in front of the word.
Edit: Actually, that was Marquis's essay, not the authors of the text.
Edit: I get the point on intervals of time, but disagree that the viability range is precisely parallel to driving. I would argue there is no rational reason to not allow abortion up to birth/hospital, since it's still a potential person, while one can easily argue about safety for driving.