Full Idea
If the only objection to killing (or not conceiving) is the impersonal one of not reducing the amount of worthwhile life, there seems nothing wrong with eliminating one worthwhile life if another is substituted.
Gist of Idea
What is wrong with killing someone, if another equally worthwhile life is substituted?
Source
Jonathan Glover (Causing Death and Saving Lives [1977], §11.1)
Book Reference
Glover,Jonathan: 'Causing Death and Saving Lives' [Penguin 1982], p.139
A Reaction
This invites us to value a life in itself, rather than for what it makes possible (e.g. 'worthwhile' activity). It doesn't follow that the life is 'sacred' - only that it has some intrinsic value. And why not?