@Nathan45
The person, was also, billions of years ago was a bunch of random hydrogen atoms floating around space. Before the zygote was formed, it was a sperm and egg, which were constructed from proteins, possibly the same ones as the chickens people buy at the grocery store.
Furthermore, 99.9% of that person wasn't the zygote, it was from other raw material added to the zygote later.
Of course, your whole body (or at least a large part of it) continouusly regenerates itself and replaces old parts with new parts. Yet that does not have an impact on your identity - you are still the same, still identical to yourself, regardless the change of matter. So when it comes to personal identity it is plausible to take the identity of a specific biological process as the condition for your personal identity. And that process started once as a zygote.
really, no, individuality has nothing to do with individual rights. Do identical twins not have individual rights?
You are correct that one zygote is different from another zygote, as stated it has a unique set of human DNA. However, from a probabilistic perspective, that unique set is no likely to be better or worse than any other set. Any sperm + any egg has a unique set of DNA, same as the zygote. I disagree that because a zygote is unique that in and of itself makes it valuable.
Actually I did not want to suggest that it is uniqueness alone that makes something valueable. In this specific case it is uniqueness and identity with a possible future person that may make it valueable - provided you think that potential persons are valuable, a thesis which can be contested of course.
And individuality has to do with individual rights of course. That which is no individual cannot have individual rights. Just to make it clear that this idea has some consequences. In my eyes the very first stages of development are ethically unproblematic even from the point of view that potential persons deserve special protection - because there are no conditions on which we can assert the biological individuality of the newly fertilized egg. It just isn't determined whether there will be one, two, three, four or more individuals. And without an individual entity, who is it to have any rights? To have rights requires a subject of rights; in this case it is not determinable whether such a subject exists.
There are no identical twins. There are twins with nearly identical DNA, but they are not identical when it comes to the question of personal identity. They are nevertheless two different biological beings.
I disagree. A zygote is just DNA in a cell. I think that conservation of matter/energy should tell you for sure that all of the materials used to form the zygote do not come from that one original cell. 99.99+% of the raw materials used to make the person do not come from the orginal zygote. I think comparing it to a blueprint is an apt comparison.
The zygote is a living process - a thing which you do not get simply by putting all the elements togehter. As far as I know there is no conclusive theory of how we can get from non-living matter to living matter in the most primitive sense (not to be confused with organic matter such as amino acids - there are theories and well tested experiments for that). Nevertheless, I think that the way matter is organized, in this case as a living process, contributes to its identity conditions. I even think that being alive is a necessary property for the persisting identity of biological beings. In simpler diction: A dead cat is never the same thing as a living cat.
I don't see why the argument from potentiality, if such a thing exists, should apply to zygotes but not to sperms and eggs.
Because a sperm in never identical with a potential future person. In fact the sperm ceases to exist when it fertilizes the egg. The same is true for the egg as an egg simply - but not for the fertilized egg insofar as it is developing normally. In that case the argument from potentiality gets in. As far as I can see, it rests on these premises (at least).
1. There is some meaningful talk of identity between actually existing zygotes and potential future persons. That could be motivated by stating that we can talk about yourselves as zygotes, looking back in the past, which seems to imply that back then we as zygotes where already identical with us now.
2. Potential future persons are ethically relevant. Of course they are not as relevant as real persons with real rights; yet the argument has to assume that they are relevant in some sense.
I do not want to deny that each one can be contested on different grounds. But my whole intention is to show that the case of abortion is not that simple as it may seem for both sides - either Christian conservative or liberal atheists.
