An interesting series of questions.

I caught this scribbled on a piece of paper, as I was cleaning my desk today.

Is there anything more valuable than human life?
If No: Then when reason have we to live?
If Yes: Then do such things justify killing in certain situations?

It’s really quite messy here: Most people want there to be something bigger than themselves (which would give us each a reason to live) yet we also want to uphold the sanctity of life. Our desires seem to be in logical conflict.
Christianity takes an interesting approach, clearly stating that certain things are more important than human life, yet giving a commandment that ‘thou shalt not kill.’ In certain other passages, though, it’s OK to kill ones enemies, if God is on your side; In the Old Testament it’s almost actively encouraged.

Though this clearly meshes with ordinary human desires (demonstrating that the book was authored by man), it remains a logical conflict. I personally don’t really have a way out. The answers that I gave on the paper were that There is something more valuable than human life (I didn’t say what) and that it does justify killing in certain situations. An answer that I obviously have problems with today (hence the post).

Even more interestingly, the paper contains a meta-question:

Is the idea that human life is the most valuable worth dying or killing for?

Clearly if you answer yes, then human life isn’t itself the most valuable (the idea is more valuable), which invalidates the claim.
If you answer no, then you undermine the importance of the idea because you would have to give it up if mortally threatened; You’d hold life itself above the idea.