On a [Western] leftist list that I am on, I have had a devil of a time convincing [some] participants that animals suffer in a manner similar to humans and that this suffering is worthy of our moral considerations. Below is Noam Chomsky on the issue, in an interview with Michael Albert (all emphasis mine):

Q: It’s also true that how people live their lives in their homes, how people regard one another, sets a framework in which even work is affected. All these things mutually interact with each other and affect one another.

And in every one of them that you look at, there are questions about authority and domination that ought to be raised constantly, and that very rarely have satisfactory answers. Sometimes they do, I think, but it has to be shown. As a matter of fact, you can even ask the same about your relation to animals. The questions can be asked there, too, in fact are being asked.

Q: You’re an animal rights activist?

I think it’s a serious question. To what extent do we have a right to torture animals? I think it’s a very good thing that that question …

Q: Torture?

Experiments are torturing animals, let’s say. That’s what they are. So to what extent do we have a right to torture animals for our own good? I think that’s not a trivial question.

Q: What about eating?

Same question.

Q: Are you a vegetarian?

I’m not, but I think it’s a serious question. If you want my guess, my guess would be that …

Q: A hundred years from now everyone will be.

I don’t know if it’s a hundred years, but it seems to me if history continues–that’s not at all obvious, that it will–but if society continues to develop without catastrophe on something like the course that you can sort of see over time, I wouldn’t be in the least surprised if it moves toward vegetarianism and protection of animal rights. In fact, what we’ve seen over the years–and it’s hard to be optimistic in the twentieth century, which is one of the worst centuries in human history in terms of atrocities and terror and so on–but still, over the years, including the twentieth century, there is a widening of the moral realm, bringing in broader and broader domains of individuals who are regarded as moral agents.

Q: Nothing could be happening to that underlying, wired-in, inate, intrinsic character… That can’t be changing.

No, but it can get more and more realized. You can get a better and better understanding of it. We’re self-conscious beings. We’re not rocks. And we can get more and more understanding of our own nature, not because we read a book about it. The book doesn’t have anything to tell you, because nobody knows anything. But just through experience, including historical experience, which is part of our own personal experience because it’s embedded in our culture, which we enter into.

Q: So then it’s plausible that vegetarians, animal rights advocates and the like are just a couple of steps ahead in discerning something about …

It’s possible. I think I’d certainly keep an open mind on that. You can understand how it could be true. It’s certainly a pretty intelligible idea to us. I think one can see the moral force to it. You don’t have to go back very far to find gratuitous torture of animals. In Cartesian philosophy, for example, where it was assumed … the Cartesians thought they had proven that humans had minds and everything else in the world was a machine. So there’s no difference between a cat and a watch, let’s say. It’s just the cat’s a little more complicated. You go back to the court in the seventeenth century, and big smart guys who studied all that stuff and thought they understood it would as a sport take Lady So-and-So’s favorite dog and kick it and beat it to death and so on and laugh, saying, this silly lady doesn’t understand the latest philosophy, which was that it was just like dropping a rock on the floor. That’s gratuitous torture of animals. It was regarded as if we would ask a question about the torturing of a rock. You can’t do it. There’s no way to torture a rock. The moral sphere has certainly changed in that respect. Gratuitous torture of animals is no longer considered quite legitimate.

[From The Chomsky Tapes Conversations with Michael Albert]