I am pro-choice so my argument here is not anti-abortion but about rejecting the argument of evictionism.
Evictionism is a justification for legal abortion based on the idea that a fetus is an invader and that the woman has a right to expel the uninvited and unwanted fetus from her womb. There are two problems with this and the first is that it is clear that the fetus is not an invader. This is where the absurdity of the argument comes in.
How did the fetus get into the womb? In all but the case of rape, the fetus came to be in the womb by the actions of the sexual partners. How can someone be an invader if your actions forced them onto your property?
So the fetus was invited, but can't you just uninvite them and ask them to leave? The fetus is, again through the actions of the sexual partners, completely dependent on the woman for its life. If your actions make someone completely dependent on very specialized care, justice requires that you provide that care for them either directly or by finding someone else who can provide that care.
If evictionism is valid then you can legitimately kill people. For example, you could invite someone onto an airplane and then halfway through the flight decide you uninvite them and evict them from the plane. As long as you did not directly kill them, the fact that they did after being thrown out is not your fault.
But the argument for evictionism is even worse. This argument, if valid, means you could force someone onto your plane, take them up then evict them even though they did not even want to go on the flight with you. No one would argue that such an act would be murder. You are obligated to carry the person until you can deliver them to safety since you put them in that situation to begin with.
What about rape? The fetus is as much a victim as the woman. The rapist is responsible for compensating both the woman and the fetus. The fetus is still not an intruder but is an unwilling victim. Putting it in the situation where it would be killed cannot be just. Using the same analogy, if a person where kidnapped by someone else and put on your plane, you would still not be able to just evict them. You are both victims.
Evictionism concedes too much to the anti-abortion movement. The claim is that the fetus is a person from the moment of conception. This clearly cannot be the case. Some time after conception, the zygote can split into two resulting in identical twins. If you are an individual person at conception, then identical twins must be half of a single individual person. But identical twins are completely different people.
What makes a person a person? Clearly, one a person becomes brain dead, they are no longer a person. We harvest their organ, hopefully, and their possessions become the property of their next of kin. So personhood does not just mean living, as a brain dead body is still alive. There must instead be some point in the development where the personhood is obtained.
