And though I'm finding this train of thought increasingly alluring, I know nothing of how philosophy ever brushed it, or it may well have tackled it head on and

And though I'm finding this train of thought increasingly alluring, I know nothing of how philosophy ever brushed it, or it may well have tackled it head on and I wouldn't know it. Philosophers have actually wrote a lot about the subject of personhood, and it sounds like you would find the discussion fascinating. Not only is the discussion practical in the future for the examples you have given, but it is also incredibly valuable to the present in terms of the abortion debate and the consent debate See: http://en.wikipedia.org/wiki/Personhood http://en.wikipedia.org/wiki/Personhood While a number of pre-19th Century philosophers have wrote about the subject (eg. Descarte, Locke and Hume), I would suggest just reading an outline of their works and delving into the more interesting discussions found in current philosophy journals.