Full Idea
If to have a right one must have the ability to desire that to which one has a right, then to have a right to life one must be able to desire one's own continued existence.
Gist of Idea
If a right entails having the relevant desire, many creatures might have no right to life
Source
Peter Singer (Practical Ethics [1979], 07)
Book Reference
Singer,Peter: 'Practical Ethics' [CUP 1989], p.141
A Reaction
The unborn, small infants, and persons in comas may well lack the relevant desire (at least consciously - arguably even a plant has a non-conscious 'desire' or drive for life). The idea that a right entails a conscious desire seems daft.
Related Idea
Idea 4668 You can't have a right to something you can't desire, so a foetus has no 'right' to life [Glover]