Hah, figured this would be a new thread after the last couple rounds of posts in the feminism thread. I'll try to keep this post short [post-completion note: four paragraphs is short for me, shut up] because I've been in tl;dr post mode the past couple days, and it looks like it's about that time again the the aforementioned feminism thread, so onward with this detour. The short and sweet of it is that I'm pro-choice. I've arrived at this stance through consideration of human rights issues and scientific metrics for what constitutes life and what makes humans different from other animals, which I'll explain with a paragraph a piece (hopefully).

Anyone who has read my recent posts in the feminism thread knows my human rights angle. People have a right to bodily autonomy, which means they cannot be forced to do things they don't want to do, their body is theirs to do with as they choose. This is why you cannot be forced to donate blood/organs/bone marrow even if you're the only convenient match, this is why hospitals can't take your organs for transplant unless you gave consent whilst alive, and it's also a core reason for the illegality of rape (unauthorized use of your body is a breach of bodily autonomy). Telling a woman she must carry a fetus is basically saying she doesn't have the right to choose what happens to her body, that the rights of this still in development pre-human entity trumps her rights. This gives a fetus superior rights to all actually birthed and living humans, because there is no circumstance in first world nations other than pregnancy which deny the rights of bodily autonomy from another person; at the same time this is taking away the rights of pregnant women, making them have less rights than a corpse in fact, because even a corpse's bodily autonomy is seen as inviolate where a pregnant woman's is not. If the circumstance were that someone had to stay hooked up to a slow blood transfusion machine to another person to allow them to live, say another adult, they could not be forced to do so even if not doing so means the death of that other person. There is no good reason why the rights of a fetus should supersede the rights of a pregnant woman, so disallowing abortion is just ridiculous from a human rights point of view.

For the science side of things, the one clear item that makes humans significantly different from other animals is our brains. Other animals can walk upright, other animals have thumbs, other animals share the various other traits we try to define as purely human. The only thing that sets us apart is our brain and what it allows us to do. Now, given that society in general has no problem with killing non-human lifeforms (just take a look at the veritable genocide of livestock animals that we then consume for proof of that), it seems to me that if something is not clearly and definitively a human then it should fall under the same general "okay to kill" tag that is applied to livestock and pests and pretty much everything not on the endangered species list. Before the brain of a fetus is formed to the point that it can actually operate as a human brain, the fetus is functionally not human yet. It lacks the characteristic that defines humanity, so by definition it's not yet a human in the same way that an egg is not a chicken. There's the potential for it to get to that stage, but it isn't there yet. From all the various research I've done on the matter, the scientific understanding of fetal brain development is that it really gets to the point of actually being a human brain somewhere in the 24-27 week area. Before then the fetal brain doesn't do much of anything, it's still forming and only has a passing resemblance to a real human brain. Thus from the scientific side of things, abortion is basically fine before the 24 week marker; even if you're more generous about it and say that once it can respond to stimulus in an instinctual fashion it's functionally human, that only bumps it back to 20 weeks. Even if you step back from the consideration of what makes a human a human, there's a strong argument to be made that if the fetus could not survive outside the womb then it hasn't reached the point of being considered viable life and thus it's fine to terminate it, and currently that cutoff is also at 20 weeks; it gets pushed way back if you take a naturalist perspective and say it has to be able to survive without mechanical assistance, though that's not a very reasonable scientific stance since you're basically saying you can't use science and medicine to keep someone alive. Whichever way you look at it, whether from the human life or viable life perspective, there's a very large window of "nope, not there yet" in which from a scientific perspective abortion is totally fine. 

For a bit of further clarification, the bodily autonomy thing is my main reason for being pro-choice. The science side of things was something I first pieced together as a sort of test/experiment when someone challenged me to give a pro-choice argument that wasn't based in morals or rights (because they dismissed the rights side of things without any real reason), so I went looking for an answer in science. I see it as a wholly valid argument for why abortion is fine before that cutoff date, but it's less solid than the bodily autonomy one due to some points that are opinion based and thus open to easy disagreement. I have found no such problems with the bodily autonomy argument though, and it also constitutes a full argument for why abortion should be allowed without the need for supplemental points, so that's my anchor for abortion discussions.