A few days ago I posted a discussion here of the problem of determining whether an animal such as an octopus has genuine pain. I claimed that the most common way of thinking about pain—the idea that we attribute pain to other species to the extent that they resemble ourselves—does not really account for the facts. To bring out that point, I proposed four simple thought experiments, essentially (1) assessment of pain in human-looking aliens with a different type of nervous system; (2) assessment of pain in human-looking robots; (3) a man who claims to experience pain but shows no external sign of it; (4) a woman who appears to be in pain but claims not to experience it. I said that I would follow up with my own answers to those thought experiments; that's what I am doing now.

The essence of my answer is that when we attribute pain to another person or another species, we are actually going beyond science. We are not simply making an assessment of the facts, we are also making a moral judgement. When we call something pain, we are implicitly calling it wrong. In order to recognize something as pain, we must see it as a combination of nociception (detection of tissue damage and response to it) and wrongness. When we ask whether an octopus has pain, we aren't just asking whether an octopus has a nociceptive system that resembles ours, we are also asking whether it is morally wrong to inflict damage on an octopus. Science can answer questions about the structure of the nociceptive system, but it can't answer questions about moral wrongness. It can give us information that helps us to come up with answers, but it can't provide us directly with the answers.

I would like to make it perfectly clear that when I say the question of pain in animals is partly moral rather than scientific, I don't mean to denigrate its importance—rather the opposite. For a scientific question such as the structure of the octopus nociceptive system, it is perfectly legitimate to say that we don't know the answer. But for a moral question such as whether it is allowable to cut off a tentacle of an unanesthetized octopus, that option is not available. If we don't explicitly forbid such actions, then we implicitly permit them. The scientific question can remain in limbo, but the moral question has immediate practical significance.

So I'm not saying that the moral question doesn't matter, I'm saying that we can't think clearly about this issue if we don't distinguish the moral question from the scientific question.

Unfortunately it's not at all uncommon for moral and scientific questions to get tangled up in this way. Let me give an example from a different domain—perhaps the most blatant example of all: the question of whether life begins at conception or at birth. That looks like a scientific question, but it really has no scientific content whatsoever. We understand the process of embryonic development in great depth and exquisite detail—attaching the label "life" at some timepoint would not add the slightest iota to our scientific understanding. We all know, of course, what this question is really about: it's about whether abortion should be permitted. It is really a purely moral question, disguised as a scientific question.

Why do moral questions get disguised as scientific questions? Basically because it is useful as a debating tactic. Arguments about right and wrong often depend on axioms that are not shared by other people, so they tend to degenerate ultimately into hand-waving and shouting. If an argument is about objective truth, though, everybody who knows all the facts ought in principle to get the same answer. I'm not saying that people who argue about the beginning of life do this deliberately or understand what they are doing—obviously they don't. But the upshot is the same.

The situation regarding pain is a little more complicated than the situation regarding the beginning of life, because here there is a genuine scientific issue—the workings of the nociceptive system—mixed up with the moral issue. But that only makes it all the more important to keep the distinction between the two issues clear in our minds.

Let me now take on the four thought experiments I described in my previous post, pointing out how the answers that most people give depend at least partly on moral judgements:

1. Suppose we are confronted with aliens from another planet, who are broadly humanoid in appearance, with two arms, two legs, an erect bipedal stance, and a head with two eyes and a mouth. They speak a language, but it does not translate easily into English, and it is unclear whether they have any word that corresponds to "pain". Suppose also that their internal organs are completely different from ours, and in particular their nervous systems bear no resemblance to ours on any level. Imagine that we poke one of these aliens in the arm with a needle, and see that the alien jerks back its arm, scrunches up its face, and lets out a screech. Should we conclude that the alien is experiencing pain?

Answer: The alien clearly has a nociceptive system that is being activated, and nearly everybody will see it as wrong to treat an intelligent alien in this way, so nearly everybody will recognize this as pain.

2. Same story, but suppose now that we are dealing with a humanoid-appearing robot rather than an alien. Should we conclude that the robot is experiencing pain? If you give a different answer for the robot than for the alien, can you justify it?

Answer: Many people refuse to think of any sort of treatment of an artificial device as morally wrong, so many people would be unwilling to recognize pain here, at least in principle. As countless Hollywood movies have shown, though, the empirical reality is that if a robot looks human and behaves in a human-seeming way, people are likely to treat it as human. So it is likely that there will be a mismatch between people's philosophical attitudes and their actual behavior.

3. Suppose we are dealing with an ordinary human, a man named Wally Wallace. He claims to be in constant excruciating pain, but we cannot see any evidence of it in his behavior. He seems completely relaxed; he laughs and jokes; he moves without any appearance of constraint; he seems happy. Nevertheless he says that he is in agony. Of course he might be lying, but is there any possibility that he is telling the truth? What would it take it convince you?

Answer: Regardless of what he is experiencing, there does not seem to be any wrongness here that needs to be fixed, so most people will not recognize this as pain.

4. The reverse scenario. Suppose Sally Sanders has a broken leg. She claims that she doesn't feel any pain at all, but she is pale and moves stiffly; she gasps and winces whenever anything touches the injured area; she seems to move in a way that keeps the injured area from touching things. Nevertheless she says that she is pain-free. Of course she might be lying, either to herself or to us, but is there any possibility that she is telling the truth?

Answer: Here, in contrast to the previous scenario, there does seem to be a wrongness that ought to be fixed, so most people would recognize this as pain regardless of the experience.

Of course not all people would give those answers, and I really can't even be sure that they would be the most common answers without conducting a survey, but I believe that they would be.

I think perhaps it is incumbent on me to say a bit about my own attitude regarding pain in animals. I am what philosophers call a "moral relativist". That's a scary-looking term, but it doesn't mean I don't believe in morals—it means that I don't believe there is any objectively absolute system of morality. I believe that our moral intuitions arise from a combination of biology and upbringing, modified by a desire to formulate them into coherent sets of rules. My own moral intuition is that it is always wrong to do unnecessary harm to an animal, and especially to take pleasure in doing harm to an animal. But activities such as fishing and cleaning fish don't feel so wrong to me that I am unwilling to do them. Regarding cooking a lobster by throwing it alive into boiling water, I would prefer a different method if any reasonable alternative was available, but as far as I know there isn't any. (I don't actually like lobster that much, and have never cooked one.)

Finally, if this discussion has whetted your interest and you would like to know more about the biological and philosophical aspects of pain, let me end with a few pointers. The Wikipedia articles on pain, pain in animals, pain in fish, and pain in invertebrates are all decent starting points. For a deeper treatment, the book The Puzzle of Pain, by Ronald Melzack and Patrick Wall, is still an excellent introduction even though it is 30 years old and out of print. Also, there is by no means universal agreement with my assertion that science cannot answer moral questions—in particular, Sam Harris's 2010 book The Moral Landscape expresses a contrary point of view, although he does not deal specifically with the issue of pain in animals.

Image: Anneli Salo