[beavus]

You are right, that principle should precede law. But in the case of temporal processes, like the life cycle, nature provides us with no sharp transitions. So what principle would you use?

Of course you could use the pragmatic approach described and just arbitrarily draw the line somewhere during the process of conception (I'm assuming you want the law to protect human embryos). Afterall, the author does say that the lines the law draws should be "typically erring on the side of caution". I guess it depends upon what margin of error is acceptable, eh?

[HangnJudge]

You are right, that principle should precede law. But in the case of temporal processes, like the life cycle, nature provides us with no sharp transitions. So what principle would you use?

It is an intrinsically difficult discussion, but even though we, reasonably, make decisions for children, we do not kill them. This biological / temporally related process does have a clear transition point in the time of conception. All things die, by chance / error / age / competition, but the ending of a life by a purposeful act is always considered to be either unlawful, or done under duress.

[D-fendr]

You told me you could tell within a week. Close enough.