Why don't humans think of all lives as equal, and instead that other creatures' lives hold more importance than others? For example a human kills an animal such as cows or pigs and no one (except animal rights activists and the like) has a problem with that, but if that same person killed another human they would be charged and sent to prison. In both cases a life is taken but (one human) and that person's life for some reason holds more importance than the animal's.

Your question seems to presuppose that life itself has some value all on its own...or maybe it doesn't, because you don't mention ending the lives of plants that we eat, or bacteria that cause infections, or stinging or blood-sucking insects. I use these examples to make a point: Virtually no one believes that life of any kind should be protected. Vast resources are spent each year on exterminating certain forms of life (for example, those that cause malaria).

So this leads to the more important (and more philosophically interesting) question: What lives should we value, and what is it about these forms of life that makes them valuable, whereas the others are not (or even have negative value)?

Now, we often think that just because we asked the question, the burden of argument shifts to those asked. My point in this response, however, is to suggest that some reason needs to be given even for thinking that we should value lives we do not now value. Animal rights activists, as you say, are trying to make this case. So far, it seems, most of us find their arguments resistible.

Of course, this reply will not satisfy you. And there are arguments that have been offered about why human lives are more valuable than the lives of (at least some) other animals. Some count the ability to be self-aware as critical (and some animals would then deserve protection); some count having a sense of one's own future (less clear on this one); some count the ability to deliberate as making a being worthy of equal moral consideration, and other considerations have been offered.

But I am inclined to go back to my first point: I see no reason why our ability to frame a challenge to one of our practices in a question about them automatically requires a defense of the practice. Instead, unless some compelling motivation to take up the challenge is provided, it seems to me the burden of motivating the challenge remains with the one who wishes to make the challenge.

Why is it morally acceptable to wear clothes made of cotton?

Ummm...why do you think it isn't?

I think the questioner is hinting at the ethical nature of killing things that can feel pain, given his examples, and he does raise the sort of issue that vegetarians and others have often found compelling. If a pig, for example, is perfectly happy nosing around in a yard are we morally permitted to kill it and eat it? Are not many animals capable of enjoying their lives, and why should we be allowed to interfere with them by killing them? This seems to me to be the challenge in the question, and it is a powerful one.

It is crucial, I think, to recognize that the relevant question here is not: Are the lives of humans more valuable than the lives of (other) animals? The objection to killing animals need not presuppose that animals' lives and humans' lives are of equal value. Most defenders of animal rights would not, I think, hold such a view. Their claim, rather, is that animals' lives are of sufficiently great value that they ought not to be killed. Note that saying that animals ought not to be killed does not imply that it is never morally permissible to kill an animal. Humans ought not to be killed, but most people would hold that it is sometimes morally permissible to kill human beings, for example, in self-defense. If (say) cows lives are of less value than are the lives of humans, then there may be circumstances in which it is permissible to kill a cow but in which it would not be permissible to kill a human being. But it does not follow from that fact that it is permissible to kill a cow just because you feel like it, or because you would like a leather jacket, or because you would like some filet mignon. Maybe it is permissible to kill a cow for such reasons and maybe it is not, but it does not follow that it is if cows' lives and humans' lives are not of equal value.

My own view, though, is that talk of "value" is not really appropriate here. I think Nicholas is right to suggest that the real question here is: What kind of life does a creature have to have in order that it should be impermissible to kill it (or to harm it in certain other ways)? The question will then be whether there are animals other than human beings that meet the relevant conditions, whatever they might be.

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