Full Idea
It seems that the bearers of rights must at least have the capacity to desire what they have a right to, which is something the foetus does not have.
Gist of Idea
You can't have a right to something you can't desire, so a foetus has no 'right' to life
Source
Jonathan Glover (Causing Death and Saving Lives [1977], §9.4)
Book Reference
Glover,Jonathan: 'Causing Death and Saving Lives' [Penguin 1982], p.127
A Reaction
Obviously we could say a person has a right to something they don't desire (such as freedom). How about: a mental defective has the right not to be laughed at, even if they don't understand the mockery?
Related Idea
Idea 20285 If a right entails having the relevant desire, many creatures might have no right to life [Singer]