Right, that's what I meant. My brain isn't being cooperative. Well, I think most people will agree that the dividing line is... well, not there. There isn't a line but a broad and diffuse frontier.
Only considering the question "When does Human Life start?"
It's understandable to consider life begins at the moment of conception, since the fertilisation has indeed occurred, and all that the cells need to become a human being is time to fully develop (considering a somewhat ideal environment).
If you don't agree with this,
(barring the "Then every sperm is sacred!" argument, which I consider invalid since there are many other impending factors to have indeed a human life [i.e. that sperm can potentially become millions of different human beings, depending on the ovum it fertilises], while if the conception already occurred, as far as I know, and forgive my ignorance if I'm wrong, there is only one human being that can develop. You can say "But time is the factor you considered! That's arbitrary!" Well, I'll concede that it isn't ideal, but at least is a lone factor, rather than many)
because of n reasons, namely "What could potentially happen isn't important.", "if it hasn't been born then it's not alive", and many others I can't come up with right now, then I guess the other choice is to consider that human life when the human being is born.
Anything in the middle (1 day-8 months and 29 days), appears to be too... hard to measure to be reliable... There is a dividing line between an embryo and a foetus, that is what many consider to be dividing, but the characteristics that are chosen to divide the two stages can be deemed arbitrary...
(Again, forgive any conceptual errors I might have done, I hated biology >_>)