As a result of some recent discussion with a colleague, I decided to post this:
Either a fetus is a human organism or it is not.
If it is not, it must be explained what it is, since it very apparently is human from its genetic content, and it is clearly an organism, rather than an organ or other tissue which constitute part of another organism, simply working from a medical perspective.
That the fetus is inside another organism does not change this fact, just as a parasite is still its own organism despite being in the body of its host.
So it seems the fetus is a human organism.
Either a fetus is a human person, or it is not.
If it is not, it must be explained what it is, since it very apparently is human from its genetic content, and it appears to be a person in the sense of being a human organism which lives in the community of other persons by whom it is shaped and whom it, in turn, shapes in some ways.
That the fetus is incapable of speech or voluntary motion does not change this fact, just as a sleeping person or someone with a disability is still a human person, despite also lacking such abilities at the moment of consideration. *
So it seems a fetus is a human person.
Either it is morally permissible to kill another human (considered as organism or as person; it is irrespective) &/or allow the human to be killed, or it is not.
If it is not, then abortion is also morally impermissible, as a case of killing a human. X
If it sometimes is morally permissible to kill another human, *
Either it is always permissible or else it is only sometimes permissible .
If it is always permissible, society would collapse. But humans are social beings by nature.
So it seems killing another human is not always morally permissible, but only sometimes.
Either killing is sometimes permissible due to the humanity of the victim, or else due to something added to it.
If it is due to humanity, then as the humanity is the same for all humans, being what makes them human, it would be always permissible. But this is contrary to the previous conclusion.
So it seems it is due to something added to the humanity of the victim.
Of things added to a nature, there are (1) quantity, (2) quality, (3) relation, (4) time, (5) location, (6) position, (7) action, (8) reception, and (9) state. These, applied to humans, can be reduced to the more general labels of (A) condition (1, 2, 8, 9), (B) situation (3, 4, 5, 6), or (C) consequence (7).
Either a consequence is the result of voluntary action or it is not.
If it is not, then it seems wrong to punish such an accident with death, even in the most severe cases, unless that accident was the result of previous action which was voluntary, as in the case of drunk driving or poor safety measures in a workplace. Even then, the death penalty may be extremely rare.
So it seems that only voluntary action can be a circumstance in which killing is morally permissible, but this is clearly something a fetus is incapable of, and this was stated earlier in the argument. X *
Either a situation is the result of voluntary action (consequence) or it is not.
If it is not, then it seems morally permissible to kill another only to save the lives of others--and even this causes sharp division among even philosophers of ethics, and may depend on precise details of the situation.
If it is, voluntary action has been already discussed. X
So while there may be a case in which a situation makes killing morally permissible if it is to save the lives of others, even this is unclear. ~~~
Either a condition is the result of voluntary action, or it is not.
If it is not, then it seems the one in the condition is innocent, and themselves a victim of external forces.
If it is, voluntary action has already been discussed. X
So it remains to be ascertained, following the same line of thought as in the treatment of situation, when it is morally permissible to kill someone who is innocent.
Either harm is being (or going to be) caused, or it is not.
If it is not, then there would seem to be no reason to kill the innocent except out of desire for killing, for its own sake. But this is utterly morally repugnant and to assert this as an acceptable reason seems little different from the assertion that killing is always morally permissible, as to kill for its own sake is to kill because of the life of the thing killed, which is always present before the act would be committed.
So unless there will be harm done by the victim, they ought not be killed. X
Either the harm which would be caused is (considered to be) to the point of death, or it is not.
If it is not, then it would seem that as possession of any good is predicated on the possessor living, the loss of any good is not enough to merit that another be killed. X
So it seems that only harm (considered to be) to the point of death might merit that the innocent be killed to save the other.
So unless the life of the mother is in danger, abortion is utterly morally impermissible by the same standards that govern killing in general.
Axiom 1. Fetuses are incapable of voluntary acts.
To deny this is to assert fetuses are capable of voluntary acts, which remains to be shown, and then requires a further development of "abortion as punishment".
Axiom 2. Killing is sometimes morally permissible, though not always.
To deny this is to assert either killing is always permissible, which is stupid, or to assert killing is never permissible, which would also rule out abortion.
Axiom 3. Death is only possibly merited by an involuntary act when it would prevent another death.
To deny this is to assert that preventing some harm less than death merits killing, but the position then needs to be developed more clearly and fully, and it appears liable to becoming an assertion that causing discomfort is grounds for being killed.