Unlike the random group of human cells you're growing in the lab over there, the zygote is a complete human individual that can grow into an adult with all the same faculties you have.
I'm not going to play your semantic game. A zygote is not an individual. An ovum with the implanted nucleus of a skin cell is effectively the same thing, and I don't consider it to be a human individual either. Do you?
Let me try and make sure I'm clear about what you're talking about. You're talking about somatic cell nuclear transfer? What some would call cloning? Why would that not be a human individual? Would you consider an adult clone to be a human individual? Why or why not? I certainly would.
Why do you resist the idea that the zygote is an individual? It is a new instance of the species, is it not? Doesn't it already have a unique set of genetic instructions that will give it different fingerprints, blood-type, eye-color, etc? Isn't its individuality already apparent?
Let's consider artificial insemination so that the events are clearly delineated. The moment someone decides to fertilize an egg, do the egg and sperm become protected just like an embryo is? I don't know the actual protocol for artificial insemination, but suppose WLOG that it's in a petri dish, and the egg is not quite through the process of fertilization. Am I a murderer if I hurl the petri dish out a window? What if the nuclei fuse while it's still 2 stories up? Am I a murder then? What if the embryo survives but is killed when an overworked nurse spills a cup of hot coffee from starbucks on the sidewalk where the dish landed? Who's the murderer now... am I, is the nurse, or is Starbuck's corporate? Perhaps the barrista who served that particular cup of coffee 3 degrees hotter than standard?
Well, if you wanted someone to bring a murder case on the basis of an accidental coffee spill, you could talk to CAnnoneer.
But if you want to ask an honest question, I regret that I can't put that fine a point on it for you. Complete fertilization would seem like a pretty obvious starting point. Though you and I apparently don't know the details well enough, I'm sure we could find someone that could make things very concrete for us. Can't say the same about personhood or viability.
As long as you're on a mission to ensure that society produces as many babies as possible, even when the parents don't want them, why limit the crusade to already-fertilized embryos? Why not turn women into baby factories?
Do I really need to respond to this? Do you want to talk about this, or do you just enjoy wasting space with nonsense? I'll quote it again, just so we can waste some more bandwidth.
As long as you're on a mission to ensure that society produces as many babies as possible, even when the parents don't want them, why limit the crusade to already-fertilized embryos? Why not turn women into baby factories?
Ooh, look, I can even turn it around on you in an equally silly fashion. Watch.
As long as you're on a mission to ensure that society murders as many babies as possible, even when the parents don't want to, why limit the crusade to embryos? Why not turn maternity wards into centers for the slaughter of new-borns?
Neat, huh?