The Australian philosopher Peter Singer is well known for his utilitarian arguments based on the principle of the greatest good for the greatest number. He is perhaps "notorious" for his attack on "specieism", which posits a fundamental difference between humans and animals. His argument was that we cannot draw a moral line between humans and animals. Not surprisingly, he became an icon for animal rights.
The foundation of his argument is not that every living thing is equal and has equal rights. It is rather the principle of avoiding pain. We respect the desire to avoid pain in others, and that means in any living organism that suffers pain. I share a profound, visceral disgust at the way so many humans treat animals (and other humans ). I am not a vegetarian to the degree of strictness that my brother David is, nevertheless I would be delighted if the international community would ever decide to ban all animal slaughter for food. In the meantime, doubtless, they, like Norway, will only focus on specifically banning Jewish slaughter, but not Muslim. And that in itself raises moral issues, but not for now.
Another fundamental idea of Singer’s, and one that I embrace as religious Jew, is what I might call gradualism. He justifies abortion on the ground that you can, indeed, evaluate human life and say that, for example, the mother’s life is more valuable than the fetus's. In fact, we humans go further; in many ways we evaluate human life and say that one person deserves to die and another does not. He fends off the charge of relativism (as does Stanley Fish in the New York Times) by saying that just because one does not accept absolutes does not mean everything is allowed.
Most absolutes (this is absolutely evil or good) tend to be of a religious nature. That is why I fear them, for their basis is rarely open to intellectual challenge. But this does not mean that some moral and ethical values may not be either superior or preferable to others, and it doesn't mean that sometimes even the worst of actions, like taking a human life, might not be justified (particularly if he is trying to kill you first).
So how do we justify killing animals? Research has shown that we share over 90% of our genetic makeup with Orangutans (but we also share nearly as much with rats, so the genetic argument is not that compelling). Chimpanzees have been shown to have emotions, learn how to invent tools and, in a very limited way, learn how to pool resources. Does this make them human? Certainly they are more human that cows or lizards.
We like to think that what differentiates us from animals is advanced intellect, capacity to reason, morality. But then what about those humans with defective or less advanced intellects? Shall we treat them the same way we treat monkeys? And if children were to be tested at birth, would they show enough advances on mature chimps to warrant special treatment? Do we decide morality on the basis of potential or achievement? And how would we treat Neanderthals nowadays, if they were still around? Would they come in at the top of the monkey scale or the bottom of the human?
In other words, we do indeed have sliding scales rather than fixed lines in morality. In Judaism, all sentient animals are to be protected from human cruelty. The ghastly undercover revelation by PETA of what went on at Rubashkin's abattoir in Postville, Iowa showed how we often ignore our own rules. The Biblical laws about sending away the mother bird from her nest, not killing a mother animal and its child on the same day, not muzzling an ox as it threshes, or yoking incompatible animals together all indicate concern. Although I admit that it is all simply a way of getting us to be more merciful to other humans.
We draw a distinction between a fetus and a living human. We also distinguish between those humans who are willing to abide by moral laws and those who are not. I often wondered how the Torah handed down such seemingly cruel treatment to certain Canaanite and pagan tribes. Why could not all humans not be treated equally? Yet if we were to think in terms of graded scales, rather than absolute categories, we would be able to recognize that in the past, and still today, there are humans so devoid of values, so corrupt that we find it offensive (or shall I say challenging) to give then the same rights we would others. Although human rights pretend to do just this, in practice legal systems do indeed treat people differently.
You might argue that law and morality are not necessarily bound to each other, and sadly often they are not. In Judaism they are. Therefore laws of cruelty to animals and humans become part of the same ethical obligation to carry out the Divine will. But then why are we allowed to kill animals, even if as mercifully and painlessly as possible? And I would go further and ask why Chasidim whirl chickens around their heads for kaparot, atonement, before Yom Kipur ? No one I know have has suggested the chickens enjoy it.
Maimonides said in his Guide (others will deny he meant it) that sacrifices were merely a concession to primitive sentiment and custom. I might say that eating meat, too, was a concession to the times (as the Midrash and Rashi say about the time after the Flood). If so, it seems to me we either have to admit we are still primitive or at least that we have not yet progressed as far as we should.