That's an interesting eventual philosophical discussion. Obviously, with animals rights we don't mean the same as human rights like liberty and the pursuit of happiness. Attempting to figure out precisely how one would apply those as inalienable rights to animals is going to be very difficult. What PETA has focused on and what the animal rights movement has focused on is the right of animals not to be eaten, worn, or experimented on (unless it is in their own best interest—similar to experiments which involve human beings), and not to be used as a mean of human amusement. And there are going to be some grey areas. One of the big grey areas right now is the fact that about 8 million animals are dropped off at shelters every year but there are only homes for about 4 million of them. So what do you do with the other 4 million animals? We know that if they were turned loose on the streets most would die horrible deaths. There aren't old feral cats, and thus, right now, until we can create a world in which people are not breeding animals and selling animals, in which everyone is going to a shelter to adopt an animal, it is in those animals best interest to be humanely euthanized. So there are some grey areas, there are some dicey discussions to be had, but at the end of the day eating animals, wearing animals, experimenting on animals—those are pretty easy philosophical and scientific discussions to have.
