As I see it, this is a question of self-awareness. Many claim that abortion is wrong because it is killing another living thing, but so is slaughtering a cow or even harvesting wheat. What they really mean is the human life is special, so I ask: What is it about human life that is special?
My answer, self-awareness. We are sentient, thinking beings aware of our own individuality. This is the reason we want dolphin safe tuna; we recognize that dolphins (as well as other primates, some birds, and probably a great deal more species than we are currently aware of), have some level of self-awareness.
How is this related to abortion? A blastocyst is not self-aware. I have not seen any study which makes the claim that fetuses are self-aware in utero. In fact, I have read that such awareness may not come until up to three months after birth. Therefore, since most abortions take place in the first trimester, long before self-awareness, there is no moral dilemma.
Let me clarify: I am not pro-abortion, I am pro-choice; there is a significant difference. I think abortions are a waste at best, but it is not my place to take that choice away from a woman. It should be a serious decision made between a woman, her loved ones and her doctor.
Medical abortions are more frequent than many people realize, and an estimated 10-15,000 pregnancies from rape occur each year (around half of these will choose abortion, while 12% or so miscarry or need a medical abortion for trauma). Incest, like rape, is also a morally justifiable reason for abortion.
Of course, many moral or ethical systems consider abortion justifiable since fetuses of abortable gestation age do not have sentience, consciousness, or the ability to feel pain.
There is exactly one structure in your body that you cannot survive without, even for a full second, and it is your brain. As Leviticus said, "I think, therefore I am". It is not necessarily rational thought, just the capability to run processes and have basic function in the brain. Fetuses do not display any of that, and so are not living.
Morality is that which minimizes unnecessary pain or suffering in other SENTIENT creatures. So until a fetus has a nervous system, it is quite literally zero objective basis for deeming it a person. Up until a certain point in the pregnancy, a fetus is no more a person than a tree is a person.
My argument is that the personal attachment that a person feels to their kin is what makes murder wrong. And also the attachment that a conscious individual feels to themselves (so that you can't kill hermits). Value arises from the valuer, not the valued. This means that abortions can be permitted where the value contributed by societal values on children is outweighed by the negative consequences of a pregnancy, for example if the parent is financially incapable of supporting a child or has no interest in a child and thus would be a poor parent, and so on. It is up to society to decide when these values outweigh each other.
The advantage that this has is that society is able to change the rules. Say for example that society experienced a catastrophe which drastically reduced our population. At that point I could understand legislation to prevent abortions. I don't know if I would support it, but I could understand it. This would come about because society values babies more highly because we needed to recover our population. Of course it should be supported by better/cheaper childcare and such but the details are not really important.
Now, I know humans are the dominant species because of intelligence which is 7 times greater in humans than the next best organism. Unfortunately we're still stupid enough to kill millions and billions of animals for food without a complaint, but freak out over a fetus that has too small of a brain to even develop thoughts and has no sense of being alive. It shows just how much humans care only about themselves and so little of everything else. Too much human population is the number one cause of problems in the world and less people is certainly no a bad thing for the big picture. So go out and care for something that is ALIVE!! (technically a fetus is alive, but it is incapable of making complex thoughts at all so its basically not what we would consider alive).
Abortion is not permissible because the Fetus is morally equivalent to a human in the sense that it is simply a human at a very early stage of life. In addition, the fetus did nothing wrong that should make it be aborted except exist, and that only happened because of the lack of responsibility between two people (with the exception of rape ect.) If you pull the self-awareness argument, then what about a human who is in a coma and that human is the responsibility of the mother for example. Should the mother have the right to choose to have her son killed? That human will wake-up eventually, in the same way a fetus will soon become self-aware.
A person dies when the heart stops beating. Why is it that life doesn't begin when the heart starts beating?
18 weeks is when the heart starts beating. But of course its not human because you don't want to face the fact abortion is legal murder. For those of you who say unborn children are blobs of cells, please do some research before you even try to make that illogical argument.
It's wrong to take the life of innocent human beings. Abortion takes the life of innocent human beings. Therefore, abortion is wrong. The only exception to the first premise is if the mother's life is in danger. It's better to save one life than to lose two, and people have a right to preserve their own life.
There is absolutely no reason to abort a child unless the following is a condition of the pregnancy.
The pregnant woman was raped.
The pregnant woman may die from continuing the pregnancy.
The pregnant woman was impregnated by a close relative (incest).
After these conditions, if they do not exist, there is absolutely no reason to abort a child. If you don't want to raise him or her, then put him or her up for adoption.
You chose to have sex.
You chose not to use protection.
You didn't have to have sex.
You could have took the pill or wore a condom.
But you didn't. And now you're responsible for that new life.
Abortion is not morally permissible for many reasons. Although the embryo/fetus is not a human yet, it has the same probability of becoming a human as DNA has of being accurate. Not only that, but animals are killed for sustenance. You cannot draw an arbitrary line at the 22nd week, when the fetus starts to feel pain, because this discriminates against dozens of people who are not capable of feeling pain throughout life. The self-aware argument is flawed, for it gives moral permission to kill someone who cannot feel pain in their sleep.