Full Idea
I am arguing that, if someone's life is worth living, this is one reason why it is directly wrong to kill him.
Gist of Idea
If someone's life is 'worth living', that gives one direct reason not to kill him
Source
Jonathan Glover (Causing Death and Saving Lives [1977], §3.7)
Book Reference
Glover,Jonathan: 'Causing Death and Saving Lives' [Penguin 1982], p.53
A Reaction
This is an attempt to find a modern utilitarian criterion of value. A problem case would be someone for whom only sadism made their life worth living.