You don't think all potential people "own" their potential, sperm/eggs for example.
A potential person, whether a fetus or a baby, owns their potential to become a person.
Babies have fully functioning nervous systems, they respond to pain, are capable of learning, etc. etc.
Are babies persons by your definition?
My ethical principles focus on awareness/conscious experience. That is the reason i put humans ahead of other animals (If you do not follow this then I do not see any other way to justify placing humans above other animals without appealing to religious ideas).
Babies are capable of being conscious therefore warrant ethical consideration.
Early fetuses are no more aware than thumb cells, therefore do not.
Why is a fetus a human "being" and not an egg+sperm pair?
The ethical concept of ownership can apply to the fetus because the fetus is a human being. The sperm and the egg are human cells, but not human beings.
1. Something can have 2 owners.
Why doesn't this concept apply to the sperm and the egg? Well, the sperm and egg's potential is owned by the respective human beings; their potential cannot have two owners. Of course, the cells could own their own potential without their human counterparts owning them.
2. One could claim exactly the same thing of the foetus (owned by the human beings).
I could consider the egg/sperm pair a single system, i could give it a name like "spetus" and then i could claim that it "owns" it's potential.
The fact that the spetus can be considered two cells should make no difference whatsoever, afterall one can consider a single cell as a collection sub cellular components if on wants to, or go further and consider it by its molecular constituents.
And they can choose whether or not to have an abortion or not.
No, as I mentioned before, these women have reproductive rights, and they can choose whether to have sex or not.
Can you not see that you are drawing a completely arbitrary line in the sand here.
In other words, the potential they have to reproduce is owned by them. They don't, however, have the right to kill another human being, because each human being owns their ethical potential to become a person. Furthermore, ownership of potential doesn't mean fulfilling the potential is necessarily a good thing, only that whoever owns the potential has the right to do as they please.
Why consider a fetus to be a human being and not a sperm/egg.
The core ethical principles i was refering to are those that are universal across all cultures.
No, I don't think so. Abortions are well attested to as being wrong in early literature. The Didache banned abortions, associating it with infanticide, and I'm aware of an early Christian authors to have used abortion (as one of many issues) to attack pagan roman culture. Presumably the author believed the roman he was arguing against had similar thoughts upon abortions. Zorastrians, too, wrote against abortions. For these authors, however, their ethical systems were more based upon gut-feelings, along with their perception of natural order. ( ie., they could reason that God created the fetus, and taking the fetus' life was wrong. )
From a utilitarian perspective that fails, because just as causing suffering is wrong reduction of happyness is also wrong.
Well, not only is that thought experiment valid but someone could go and kill everyone, eliminating all loved ones
Heard of IVF?
If the sperm and egg owned their potential to create life, then a doctor could, without the patient's consent, manage to create another human being using a patient's cells.
Another arbitrary qualifier, one could easily choose to define the fetus as part of the mother. How we classify stuff is completely up to us.
Biologically, the fetus is another human being, not part of the mother. Consequently, the dna of the fetus is different from the mother's dna.
Oh yea and Cheez:
You're kidding right?
I'd like a link to back up this figure, please.