For the problem with that argument, see post #43...the zygote is self-sustaining and growing prior to implantation.
Also, I think this self-sustaining bit is not a good criteria generally. A newborn won't do so well if it doesn't get outside intervention in the form of warmth and food. Toddlers can't fend for themselves. Every organism is dependent on a small range of environmental and biological conditions to live. Every one. Take it out of those conditions and it is dead. There's no such thing as a fully independent existence.
“self-sustaining individual who would, in the absence of outside intervention, become a fully-independent person.”
I’ll add to your response to this. If this were the “clear line” moving from chosing to eliminate parasites to murder, then according to the collectivists we could kill anyone at any time!
I guess that is their end goal....
We mostly agree, and I'm undecided on which end of that 1-5 day period life begins. In practical terms, it almost never matters whether one accepts what I called definition (1) or definition (2). In either case, surgical abortions are in almost all cases killing an innocent child and chemical abortions are at least potentially the same moral crime. Note: in rare cases, such as ectopic pregnancy, this killing of an innocent is, in my opinion, fully justified to save the life of the mother when the baby's life cannot be saved.