Full Idea
On the whole, since we mean by a right something that can be justly claimed, we should probably say that animals have not rights, not because the claim to humane treatment would not be just if it were made, but because they cannot make it.
Gist of Idea
Rights can be justly claimed, so animals have no rights, as they cannot claim any
Source
W. David Ross (The Right and the Good [1930], §II App I)
Book Reference
Ross,W.David: 'The Right and the Good' [OUP 1930], p.50
A Reaction
This would also apply to a human being who was, for some reason, unable to claim their rights. If Amnesty can claim rights for prisoners, presumably we can claim rights for dumb animals. Ross is on weak ground.