The arguments presented in this book would seem to have consequences for how we think about ethics. Since I know nothing about this tricky field, I have put this very tentative section in an Appendix, to be considered for what it's worth.
The bottom line: I have been suggesting that what we human adults call "feel" involves an agent with a self having conscious access to a sensory interaction with the environment. As concerns beings like animals and newborn babies, depending on an their cognitive capacities, and depending on the degree of development of their notion of self, their consciousness will be more or less developed. Does this mean that some animals and babies actually feel nothing?
To go over the argument in detail, take again what I called the Mark I Chessplayer, which was a hypothetical future robot with a head, torso and arm, and which could play chess with you. Is the machine consciously experiencing anything as it goes about its activities?
By the definition of feel I have suggested, in order to consciously experience a feel, an agent has to have sufficient cognitive capacities to have constituted at least a rudimentary notion of itself, and it has to have the ability to have cognitive access to the quality of the interaction that it is engaged in. I argued that the machine had cognitive access to your moves, but not only did it have no cognitive access to what "it" was doing, but worse, it had no notion of "it" at all.
The answer therefore is that Mark I chessplayer does not consciously experience feels.
The same would be true for an animal like, say, a gnat, which is, I suppose, essentially a biological machine that goes about its everyday activities in an entirely automatic way (albeit making use of sophisticated mechanisms that a roboticist would dearly like to fathom). It has no cognitive access to the quality of its interactions with the environment, and it has no self. It cannot consciously experience feels, under the definition I am using.
Presumably if we made the chess-playing machine progressively more sophisticated, or if we considered animals higher on the phylogenetic scale, the degree to which it makes sense to say that they have a "self" increases. In parallel, the degree to which the agent has the cognitive capacity to mentally "stand back" and cognitively access the fact that it is cognitively accessing some quality of its current interaction with the environment, will also increase, and so will the degree to which it makes sense to say that the agent consciously feels the experience.
So as we go up the scale in cognitive capacity, in social insertion, in the variety of choice that an agent has within its environment, and to the extent that it can stand back from its immediate perceptions and make use of them in its rational behavior, the degree increases to which it makes sense to talk about "conscious" experience.
There seems to be something deeply problematic with this claim: It suggests that sufficiently primitive animals and sufficiently young fetuses or even newborns, because they only have a very limited notion of self, should feel only in a correspondingly limited way, and possibly in some cases not all. The claim seems to fly blatantly in the face of common sense: we all believe that dogs and cats and babies feel things.
But the point is the following: I am suggesting that the way we as adult humans use the concept of conscious feel implies having the notion of self. In the case of an animal or baby, the animal or baby's organism is undoubtedly reacting in response to sensory stimulation, but there is not very much of a self for the organism to feel it, at least in the way we as adults feel. The animal's or baby's body is reacting appropriately. For example, in the case of pain, the organism is providing an avoidance reaction, registering a stress response, signaling by its crying that it requires help from its conspecifics. But, since there is no structured "I" to know and cognitively use the fact that these things are going on in the body, we logically cannot say, under the definition I'm proposing, that the animal or baby, considered as a "self", feels anything in the same way as adult humans feel it. In the case of pain, perhaps there is suffering that is somehow "taking place", but there's no animal-self or baby-self to feel that suffering. This is a logical point -- it is a consequence of adopting the definition I'm proposing of what we mean by feel.
Now you may not want to adopt this definition. But the trouble is, the definition really does seem to correspond to how we usually apply the word "feel" to human adults. Normally when we say we feel something, what we mean is that "we" feel it! In contrast, think about biological mechanisms like digestion, respiration, and cell replication that go on inside of us, but of which we, as selves, are not conscious. There are certainly parts of my brain that are occupied with these processes and dealing with them appropriately. But unless "I" pay attention to exactly how I am sitting right now, I am not aware of the little movements that I make to adjust my posture. My breathing goes on automatically without "me" generally being aware of it: I do not feel it.
Or imagine you are playing rugby, and in the heat of the action, injure your leg. It can happen that you don't become aware of the injury until later. Only later do you realize that there is a bruise on your leg and that your running has become less smooth. "You" as a self, were not consciously aware of any pain when the injury took place. At that time, your body reacted appropriately, dodging the people running behind you, hugging the ball and sprinting forward. But "you" were momentarily "out of your office", so to speak, as far as the injury was concerned; "you" were paying attention to running after the ball or to the strategy of the game.
In other words, when your self is off paying attention to something else, you do not feel your breathing or your injury. When "you" are not at the helm (or rather when "you" are away at a different helm) "you" feel nothing about what's happening at your helm. So if what we mean by "feel" is what we as conscious human adults usually call feel, then since primitive animals and newborns do not have much of a "you" to be at the helm at all, "they" will be in the same situation as you when you are away from the helm: they will feel nothing.
In order to avoid what seems like the rather shocking conclusion that newborns and animals really don't feel anything very much, perhaps we could conceive that there might be some other kind of feel that happens in organisms that don't have selves.
Such an "organism-based" kind of feel would not require "someone at the helm". It would be some kind of wholistic life-process going on in the organism that could be said to be experiencing something. Under this view, even though "I" don't feel my breathing or the injury to my leg, my body somehow does. And in the case of primitive animals and babies, independently of whether or not they have fully developed selves, their organisms still could in some sense be said to experience feels. In the case of pain, it would be this organismic-based suffering which would be occuring.
The trouble with defining such a kind of feel is that it's difficult to know exactly what we mean, and where to define the limits of where we want to apply the term. What exactly distinguishes an organism-process of which we want to say that it experiences feel, from one to which the notion does not apply? Please note that this is a question of trying to pin down a definition of exactly what we mean by the notion of organism-based feel. I'm not asking which organisms have it and which organisms do not. I'm not asking what types of nervous system or biological systems are necessary for having organism-based feel: I'm asking how we want to define the notion.
So let me devote a few lines to thinking about how we might want to define organism-based feel.
Perhaps what we mean by organism-based feel is the ability of an organism to react to outside influences in an appropriate and adaptive way so as to preserve its normal existence and functioning within its ecological niche. This would certainly apply to many animals, and clearly to fetuses and newborns. The trouble is, it would also apply to plants: after all, plants adapt to environmental conditions, for example by turning to the light. They also can ""suffer": they register stress by wilting when deprived of water and modify their metabolism when injured, and they can even signal their stress to nearby plants and affect them by emitting chemicals into the air.
In fact the definition of feel as involving an adaptive reaction could even be applied to rocks. There are forces inside the rock holding it together in its global form, and stresses and strains inside it modify the way electric fields, heat and vibrations spread through the rock. When you tap on a rock, vibrations are sent echoing all over inside the rock in a way specific to that rock. When you apply heat at one spot, expansion takes place and propagates across the rock. There are slow chemical reactions going on inside the rock also, as bits of the rock with different chemical composition diffuse molecules gradually through its interior and mix and react with others. Thus, there are various wholistic, global processes that characterize the way the rock adapts to outside influences, and one might want to say that when they are interfered with and modified by things happening at the surface of the rock, the rock feels something and adapts.
So let's try to refine our definition of (organism-based) feel so that it conforms more to our intuitions. We want a definition that excludes plants and rocks, and only applies to fairly high-level organisms, perhaps starting with fish but excluding insects. We are tempted to say that a moderately complex brain is needed that centralizes information, so that the organism's adaptation is not simply a reactive behavior, but is more flexible, with the ability to learn from past experiences.
The trouble is that many computer systems would still satisfy the definition. They react to outside events, adapt and can even learn from them.
To further refine our definition so as to exclude machines, the natural intuition is then to require that the organism must be biological. It must be alive, and have capacities like being able to breath and replicate and metabolize.
But wait a minute! What have we been doing here? In order to come up with an understanding of what we mean by the term "organism-based feel", we have slipped from noting the capacities that we define as constituting feel, to stipulating what an organism should be made of, whether it has a brain, is alive, is made out of biological material... But such restrictions are not part of what constitute feel, they are just intuitions we have about what is probably necessary in order to obtain the capacities that constitute feel in a real organism or device.
So we should be careful not to fall into this trap: The correct way to proceed is to reflect on what we mean, that is to say, to make very precise the statement: "having (organism-based) feel consists in having such-and-such capacities" (whatever they are). Only then would we check whether building in "such-and-such" capacities requires having a complex nervous system, or being alive, or being made out of biological material.
Furthermore there is an ethical danger of confusing the capacities that constitute feel with the biological (or other) material necessary to obtain those capacities. If you let our intuitions about biology guide us, it is suspiciously like singling out organisms which are just like us.
Remember the Valladolid controversy in the 16th Century about whether South American indians were actually human beings with souls? Clearly in that era many rational and intelligent Europeans were convinced that the indians were not enough "like them". Remember the Nazi era? Remember thirty years ago when doctors thought that babies felt no pain and operated on them without anesthetics?
Clearly, using our (strongly culturally bound) intuitions about whether an organism is physically like us is neither a logically sound way of characterizing organism-based feel, nor is it ethically safe.
But much more important is the following point: Even if we did end up finding a satisfactory definition of organism-based feel, this organism-based kind of feel is completely different from what conscious adult humans usually mean by feel. Indeed it is a very odd kind of feel: precisely because it is organism-based and not felt by the self, a conscious adult human would actually say that he or she (as a self) doesn't feel it.
This organism-based type of a feel is a feel that you don't feel! What could that mean? I think the notion is not of much use.
We are thus faced with the question of the rights of animals, fetuses and newborns. If animals, fetuses and newborns do not experience feel at all, or at least not in the way we as adults do, then this raises the question of pain: Do these arguments imply that there's nothing wrong with me kicking my dog, no problem with abortion, and no need to use anesthetics on babies?
In order to counter this, a first argument one might try is the following. Deciding whether or not we should be nice to animals and newborns is not so much a question of whether they actually feel pain, but whether by inflicting noxious stimulation on them we are thwarting their desires. The case of masochists provides an argument in favor of this idea: surely inflicting pain on masochists, when it is at their request, is not reprehensible. This shows that what counts is not the suffering caused by pain, but whether a person does or does not want to endure the suffering.
Can we use this as a way for justifying why it is bad to inflict pain on animals and newborns? Can we say that since animals and newborns avoid pain, that they do not want it, and conclude from this that it is bad to inflict pain on them?
I think not. Animals' avoidance behavior shows that their organisms are constructed to avoid noxious stimulation. But it can't be deduced from this that "they" as agents "want" to avoid the noxious stimulation. In particular, sufficiently primitive animals and sufficiently young newborns or fetuses probably do not have sufficient mental capacities to conceive of "them"-selves as existing, let alone as having wants and desires. In the absence of a self to want something, it makes no sense to use that term. As an analogy, consider me driving my car engrossed in conversation, but unconsciously, though appropriately, avoiding the truck in the middle of the road. Does it make sense to say that "I" wanted to avoid the truck? Not in normal parlance, I would claim. It is only a very loose way of saying that "I" avoided the truck in this way. What I generally mean when I say "I" consciously do something, is that I was aware of choosing to do it.
You could argue, somewhat analogously to above where I extended the meaning of feel to organisms without selves, that we can conceive a sense of the word "want" or "choose" in which an organism without a self "wants" something. Then we could say that my mind/body somehow "wanted" to avoid the truck. But such a sense of the word "want" leads down another slippery slope: you might readily admit that in this sense of "want", an ant going along its trail could be said to "want" to find food, or a plant "wants" to grow to adjust to the light. Such a sense of the word "want" can even be applied to my refrigerator, which "wants" (has been designed with a mechanism) to keep the temperature cool inside it, or to the rock, which "wants" (has the natural tendency because of the mechanism of gravity) to fall to the ground when I let go of it.
Thus it seems that again we cannot say that pain is bad for an animal or newborn because "it" doesn't want it: the term "want", used in the normal way, seems inapplicable to organisms that do not have selves. And if we use the term in a wider sense, then we have to justify why we should not apply it to refrigerators and rocks.
In an effort to save our intuitions about the fact that it is bad to inflict pain on animals and newborns we might consider loosening our use of the word "want" so as to allow a meaning like: what an organism "wants" is what it is built to do under normal circumstances given its ecological niche and evolutionary history. Then we could claim that interfering with this normal operation is reprehensible. Animals, fetuses and newborns are presumably built to have lives without noxious stimulation, so it is bad to inflict this on them.
The trouble is that this argument leaves open the question of what we mean by normal functioning. Take the case of a fly. It goes about its flying-around activity in a more or less automatic way. What it does as it flies around corresponds to the natural order of things that happen when you have a biological device that is programmed to do the things that the fly is programmed to do. If you pluck out one of its wings it will then go about doing something else, also in a more or less automatic way, but this is no longer the normal functioning. Or is it? After all, the new way of doing things corresponds to the natural order of things that happen when the fly's nervous system acts with one less wing working. Depending on how we define normal functioning, we may or may not have to have compassion on flies with a wing missing.
Another problem is that the argument about "wanting" to tend towards "normal operation" can be applied to devices like vacuum cleaners and computers, and even to rocks. Why should we restrict "normal operation" to mechanisms that have been formed by natural selection through evolution. What's so special about evolution? Why could we not also include, for example, household use (for vacuum cleaners) and geological processes (for rocks): the "normal operation" of rocks is, presumably, just to sit there. Under the argument I'm suggesting, it would be reprehensible to shift them. Do they also "want" to resist erosion?
In the previous paragraphs I have been searching for an argument against inflicting noxious stimulation on primitive animals, fetuses and newborns. But we have seen that neither appealing to the painfulness of pain, nor to the fact that people do not want it, works as an argument if there is no self to experience the pain or to want it to stop. The appeal to "normal functioning", although it has the advantage of not requiring the notion of self, leaves open the question of what is meant by this exactly, and does not help us decide which animals (or even devices or objects) we should and should not have compassion on.
Another tactic to justify why we should be humanitarian to animals and newborns is to appeal to a weaker and more general argument, not specific to pain, based merely on the idea that it is bad to damage things that we consider important for the workings of our society. I admit it is somewhat unsatisfactory to appeal to such a general argument, when intuitively one is searching for an argument that is rooted in the very special case of pain. But we have to take what we can get.
Our society is built around the priniciple that we want to protect what we depend upon to make it function. This idea applies to non-living things like land, rivers, cultural objects like literature and historical monuments and sites, as well as to goods or objects of any sort. It applies also to living things like forests, animals and even viruses and bacteria whose biodiversity we protect out of a concern for the future of our habitat. And of course it applies most critically to the protection of our own human species. This protective ethic is basic to our society and quite independent of whether or not what we are protecting has any conscious feel. Whereas in the past, human societies considered it ethical to exterminate other tribes, other races, and destroy their habitat and traces of past civilisations, today, global communication is founding a more tolerant society in which there is more respect and greater solidarity among humans, and this extends even to animals and to the earth's resources.
Thus, an argument for condemning injury to animals and newborns arises out of the basic protective ethic of our present society. The argument is easy to apply when it's clear that injuring or inflicting noxious stimulation on an animal or baby is bad for its survival and for the role it plays in our society. Operating on a baby without an anesthetic, even if it's true that the baby, not yet having a proper self, cannot be said to feel anything, is not a good idea, because the baby's organism will be stressed by the operation, and this may delay healing and even impact on the baby's personality when it grows up into a child. Kicking my dog will alter its social behavior, making it more edgy and mal-adapted, and perhaps more likely to bite my neighbours in the future.
But what about cases where inflicting noxious stimulation is considered socially necessary, as in slaughtering animals for food, or actually thought to be good for an individual's mental health, as in spanking children or punishing criminals, or thought to be good for an individual's physical health, as in performing surgical operations to cure disabilities? And then there are borderline cases like fishing and bullfighting, where inflicting noxious stimulation on an animal is done gratuitously for human pleasure?
The ethics of such cases is obviously very tricky. Unless one can appeal to absolute deontological principles, the decision on what is considered good and bad must be based on weighing the pros and cons within a social context.
This then is a very general argument against inflicting noxious stimulation on animals. It is really just a special case of the idea that it is bad to harm what our society depends on.
There is another argument, based on empathy, that can be made for being nice to animals and newborns even when there is no "self" within them to register pain. Empathy is an essential ingredient of our social ethic: humans believe that it is important to respect the feelings of other humans. This respect is what leads us to condemn aggressive behavior towards other humans, and to protect the vulnerable. The importance our society gives to empathy as a human trait is so great in fact that in recent times we are extending our empathy to other species, and we tend to do so even in cases when it is displaced, as when applied to objects that cannot benefit from it. For example we condemn the behavior of a child that tortures its teddy bear or gratuitously plucks out insect wings, on the grounds that such behavior is distasteful and sets a bad example, even though certainly the teddy bear, and presumably also the insects, have no feel.
Finally there may be another argument for being nice to animals and newborns. I give this argument somewhat tentatively.
If we take seriously the idea that the self is really a social construct, then what we consider to be our selves are in fact constructions that our brains have made in relation to other people. What "I" consider to be "my" self is actually a way of talking to other people about what my body does. The nature of my self is essentially determined, not mainly by me, but by what other people find useful to say about me. It is not really correct therefore to say that my self is "in" me, since it is really more something "between" me and other people.
If this is true then even our own pain, even though we feel it very acutely, is actually a social construct and merely a way of talking to other people about the things we tend to do when we are subjected to noxious stimulation. The felt hurting of the pain, and our thinking and saying that the pain hurts are two aspects of describing such situations, but in fact our being convinced that the pain hurts, and the thinking and saying that it hurts are just ways other people (and coincidently our selves as well) can talk about our situation. Asking whether the pain "really" hurts is not a question about what is going on inside me, it is a question about how best to describe from the outside what I am doing or what I might tend to do now. In the case of chickens that can't think or say that the pain hurts the situation is not so different then. From the outside (at least as seen by humans), the chicken "really" is in pain (since reality is in the way things can be described from the outside), even though it can't think or talk about it. Thus, the chicken really does feel the pain to the same extent that I really feel my own pain, which, after all, is also nothing more than a way of talking about what, seen by others from the outside, I am doing now or likely to do now.
These ideas are obviously very tentative, and I offer them here merely as the basis for further consideration. They go against the grain of Western thought, but may perhaps be in line with some eastern traditions that question the "reality" of the self.
This discussion on pain brings home the great responsibility we have as humans in deciding upon our ethical codes. When we cannot appeal to absolute values -- in this case to the existence of some precise divide in the animal kingdom between animals that feel and animals that don't feel, or some precise moment in the foetus's or newborn's development after which it suddenly becomes able to feel -- we are left with the acute difficulty of making arbitrary decisions to establish lines of conduct based on what we wish to define as a humanitarian ethic. If we cannot appeal to God, to Science or to some absolute Truth, we are left to decide, all by our lonely human selves, what we wish to define as humanity. We have to agree, simply as a matter of social consensus, how much we wish to extend to other species what is probably the hallmark of humanism, namely our empathy.
 There is an immense and very contentious literature on the question of which animals have which level of meta-cognitive capacities (for discussion see e.g. Heyes,C.M.(1998).Theory of mind in nonhuman primates. Behavioral and Brain Sciences, 21(1), 101–134.; P. Carruthers, Meta-cognition in animals: a skeptical look. Mind and Language, 23 (2008)), and what degree of notion of self (for a discussion see Alain Morin, Levels of consciousness and self-awareness: A comparison and integration of various neurocognitive views. Consciousness and Cognition 15 (2006) 358–371. I think it is senseless to try to draw a line somewhere through the animal kingdom and say, these animals have conscious feel and these do not.
 For a review on fetal pain see: Lee, SJ, HJP Ralston, EADrey, JC Partiridge, MA Rosen, Fetal Pain. A systematic multidisciplinary review of the evidence. Journal of the American Medical Association. 2005;294(8):947-954 (available on line at http://jama.ama-assn.org/cgi/content/full/294/8/947). There was an acrimonious debate in British Medical Journal in 1996 about whether fetuses feel pain, with its accompanying ethical question of the justification for abortion, following the article by SWG Derbyshire, Do fetuses feel pain? "Fetal pain" is a misnomer. British Medical Journal 1996;313:795-9. The minimum necessary condition for pain that everybody agrees on is that an agent should manifest a stress reaction and avoidance behavior. This is assumed to require a working connection between sensors, thalamus and muscles. Some people think that some kind of "conscious" perception of the pain is additionally necessary. Conscious perception is generally thought to occur in the cortex, so to have this, connections between thalamus and cortex are thought to be additionally necessary. But all these are just necessary conditions, not sufficient ones, so in fact none of these arguments even guarantees that even neonates feel pain. Hardcastle, V. G. (1999). The Myth of Pain. Cambridge, Massachusetts: MIT Press, devotes a section of her chapter 8 to the question of whether babies feel pain, and concludes that even though their bodies may register the stress of pain (which is what she calls "to feel pain"), they would not be able to consciously feel pain, at least in the way adults do.
 Though part of this effect may be accounted for by physiological reduction in pain sensitivity caused by the excitement of the game, a significant portion is due to the fact that "you" are not paying attention to the injury. A review of the attention and emotional effects on pain is: Chantal Villemure, M. Catherine Bushnell, How do attention and emotion inßuence pain processing? Pain 95 (2002) 195–199. A review of the brain effects of attention-demanding tasks on pain perception is: P. Petrovic & M.Ingvar, Imaging cognitive modulation of pain processing. Pain 95 (2002) 1–5. A careful review of controlled experiments on hypnotic reduction of pain, showing that hypnosis really works is: David R. Patterson and Mark P. Jensen, Hypnosis and Clinical Pain. Psychological Bulletin. 2003, Vol. 129, No. 4, 495–521
 Note that I don't say "inflict pain" -- since I'm supposing that animals and newborns don't actually feel the pain, at least not consciously, since there is no "I" to be conscious of it.
 The argument that frustration of desire is what deserves compassion was made by Carruthers, P. 1999. Sympathy and subjectivity. Australasian Journal of Philosophy 77, 465- 482, (see also Carruthers, P. 2004c. Why the question of animal consciousness might not matter very much. Philosophical Psychology) contradicting an earlier paper of his own where he argues that "brutes" are not worthy of compassion (Carruthers, P. 1989. Brute experience. Journal of Philosophy 86, 258-69).
 Carruthers seems to use the word "desire" in a way that does not require a self. The only reasonable way I can think of in order to make sense of this is what I suggest here of extending the notion of "desire" to mean: corresponding to the functioning that an organism is built to pursue. This is because taking what would seem to be the more intuitive definition of "tending to pursue a goal" involves the notion of "goal" which surely presupposes some kind of hypothesis about what the organism's normal functioning is.
 For some references see the review Walco, Gary A., Cassidy, Robert C., Schechter, Neil L., Pain, Hurt, and Harm -- The Ethics of Pain Control in Infants and Children. New England Journal of Medecine, 1994, 331: 541-544
 An excellent survey on environmental ethics in the Stanford Encyclopedia of Philosophy discusses different approaches to these problems: http://plato.stanford.edu/entries/ethics-environmental/
 A very similar idea, though not presented in terms of empathy but in terms of "good character", is suggested by P. Carruthers in chapter 7 of his book: The animals issue: moral theory in practice. Cambridge University Press, 1992. Available on line at: http://www.philosophy.umd.edu/Faculty/pcarruthers/