Gaudere, this response may be familiar to you (I won’t presume that you’ll remember our prior exchange). Your points are familiar to me, in any event, which is undoubtedly the reason that I will respond as I did before.
Here goes: Any entity with the potential for sentience is “alive”–meaning, deserving of protection and possessing the right to live. If this potential exists, it trumps all other rights (except, perhaps, the right of another entity to live).
We determine this as best we can–through medical measurement, if possible–though our determination is often unavoidably shaky. I would hold no one “guilty” who tried their best to make this determination in good faith, though a crystal-clear conclusion may be an objective lost at the start.
This category of human beings includes most pre-born children, regardless of their stage of development, as well as adults who are deemed brain-dead in an EEG but who ultimately recover. (An admittedly extremely rare ocurrence that I have NOT researched extensively. Here’s one cite that references “600 comatose patients with flat EEG reported in a preliminary study by the American EEG Society, supplied to Henry K. Beecher by Robert Schwab” for anyone who supposes this is hypothetical. This cite also mentions hypothermia as a condition that could create a flat-line–i.e., non-sentience–without creating irreversible brain death. Again, I am no expert.) I believe we could kill neither without raising moral concerns over the right of a human being to live.
If current sentience is a sacred attribute, one that by itself defines personhood, we could easily permit the death of the brain-dead adult, even if we were certain of his recovery (this is, currently, completely a hypothetical, in that we don’t have the technology to make that determination conclusively; certainly an extremely large majority of EEG flat-liners will NOT recover, but the moral point retains its validity just the same, IMO).
The category would exclude children born without brain stems (I think–I am not sure I know exactly what this means, but I take it to mean that these children will never be capable of sentience).
You may counter by saying this is axiomatic and compelling only from my point of view. My response to that would be to agree that it is at least that, but also to point out that it is no less axiomatic than “sentience = personhood” and that there is virtually no law or moral rule in existence that cannot ultimately be traced to an axiom.