As of late, I’ve been getting really interested in animal rights philosophy, not because I’m close to turning into a vegan or anything, but simply because I find philosophical arguments that depend on comparative animal psychology to be really interesting. And I’ve been interested in the philosophy of animal minds for a long time, so the connection to my research is obvious. In particular, the Argument from Marginal Cases (AMC) really interests me. The AMC is one of the primary arguments used to support the idea that nonhuman animals have rights just the same as humans. I found the following summary of the AMC in a paper by Daniel Dombrowski:
1. It is undeniable that [members of ] many species other than our own have ‘interests’ — at least in the minimal sense that they feel and try to avoid pain, and feel and seek various sorts of pleasure and satisfaction.
2. It is equally undeniable that human infants and some of the profoundly retarded have interests in only the sense that members of these other species have them — and not in the sense that normal adult humans have them. That is, human infants and some of the profoundly retarded [i.e. the marginal cases of humanity] lack the normal adult qualities of purposiveness, self-consciousness, memory, imagination, and anticipation to the same extent that [members of ] some other species of animals lack those qualities.
3. Thus, in terms of the morally relevant characteristic of having interests, some humans must be equated with members of other species rather than with normal adult human beings.
4. Yet predominant moral judgments about conduct toward these humans are dramatically different from judgments about conduct toward the comparable animals. It is customary to raise the animals for food, to subject them to lethal scientiﬁc experiments, to treat them as chattels, and so forth. It is not customary — indeed it is abhorrent to most people even to consider — the same practices for human infants and the [severely] retarded.
5. But absent a ﬁnding of some morally relevant characteristic (other than having interests) that distinguishes these humans and animals, we must conclude that the predominant moral judgments about them are inconsistent. To be consistent, and to that extent rational, we must either treat the humans the same way we now treat the animals, or treat the animals the same way we now treat the humans.
6. And there does not seem to be a morally relevant characteristic that distinguishes all humans from all other animals. Sentience, rationality, personhood, and so forth all fail. The relevant theological doctrines are correctly regarded as unveriﬁable and hence unacceptable as a basis for a philosophical morality. The assertion that the difference lies in the potential to develop interests analogous to those of normal adult humans is also correctly dismissed. After all, it is easily shown that some humans — whom we nonetheless refuse to treat as animals — lack the relevant potential. In short, the standard candidates for a morally relevant differentiating characteristic can be rejected.
7. The conclusion is, therefore, that we cannot give a reasoned justiﬁcation for the differences in ordinary conduct toward some humans as against some animals
So here’s why I think the AMC is rather weak.
I don’t have any problems with premise (1). Premise (2) is already problematic though. The claim is that “human infants and some of the profoundly retarded [i.e. the marginal cases of humanity] lack the normal adult qualities of purposiveness, self-consciousness, memory, imagination, and anticipation to the same extent that [members of ] some other species of animals lack those qualities.” While it is undoubtedly clear that a human baby possesses less self-consciousness, imagination, and anticipation that human adults, there is a lot of evidence to support the idea that human babies are remarkably well-developed cognitively, they just lack the capacity of expression. So a human baby is certainly more intelligent than a chicken, and possibly more intelligent than a cow. The problem is that human babies have no way to express their intelligence since they can’t speak yet nor can they use their motor skills to communicate. But subtle experiments demonstrate the extent of their cognitive sophistication.
Moreover, the AMC ignores an obvious extension of the “marginal case” of the human baby: human fetuses. It seems like many speciesist would not include human fetuses in the moral sphere precisely because of how marginal their cognition is. And the development of human-like cognition is one of the markers for where we start drawing the line for abortion. The more developed the brain becomes, the less we feel it’s right to abort a child. And it could be said that the actual birth is an arbitrary cut-off point. If a baby was born without any brain, then it’s likely we would not include that baby into the moral sphere and mercifully end its life without its explicit consent.
But what about mentally retarded people like those with severe autism or Alzheimers? Clearly these entities lack the uniquely human cognitive capacities that characterize a normal human adult, yet we don’t treat them like cattle. Isn’t this inconsistent? Hardly. In the case of most autistic children, I believe the evidence shows that they either have a reduced human cognitive skill set or a different cognitive skill set, but it is rare that they have no skill set at all. I would daresay that your average autistic child is more cognitively sophisticated than a chicken. And the same for your average Alzheimers patient. Likely, an Alzheimer patient, for the majority of their disease progression, has a reduced cognitive skill set, but they don’t lack one altogether. And when such persons do eventually completely lack consciousness, why would a speciesist assume that they have full moral rights? Personally, if I ever developed Alzheimers, I would hope that my society permitted assisted suicide or mercy killing once I reach a totally advanced stage of the disease. Likewise for vegetative coma patients. It seems as if humans who totally lack consciousness are not fully included into the moral sphere, as, say, a normal human adult. This explains our attitudes towards those in comas with no foreseeable chances of recovery.
Thus, I think premise (3) is wrong in almost all cases. Moreover, we can use a different strategy to show why it’s consistent for a speciesist to treat newborn infants differently than they treat cattle: counterfactual biological development. Under normal healthy circumstances, a human infant will grow into a cognitively sophisticated adult. Under healthy circumstances, it is very very unlikely that a cow will grow into a cognitively sophisticated adult. And if that cow ever does mutate and develop the ability to rationally talk and engage humans in high-level moral conversation, then we should include that cow into the moral sphere. But what about someone with severe mental retardation who has no potential to grow into a normal adult? Well, as I said before, it’s doubtful that most retarded children are as cognitively stupid as a cow or chicken. Moreover, we can engage in a counterfactual analysis and think that it would have taken much less different alignment of genes for a retarded child to have been born with the potential to grow into a normal adult than it would be for a chicken or cow. A cow would have to have a total restructuring of the genome in order to produce a brain capable of learning human-like cognitive skills. So the counterfactuals are in fact quite different.
And there is another point where the AMC fails: it paints a false dichotomy whereby either animals have rights equivalent to adult human rights or they have no rights at all. This is a false dichotomy, because we can imagine a continuum of rights rather than an on or off switch. It makes sense to me that although a bonobo or dolphin has less rights than a human adult, it has more rights than a chicken, and a chicken has more rights than an oyster. I would never treat a bonobo like I would a chicken or a mosquito, but I would not treat a bonobo like a human child or a human adult. If there was a burning building, I would rescue a normal human adult or child over a bonobo, but I would rescue a bonobo over a chicken. Moreover, it’s false that this reasoning is arbitrarily speciesist because I would rescue a bonobo over a vegetative coma patient or a human fetus.
Now I want to discuss premise (5): human uniqueness. I see it claimed a lot in animal rights literature that the attempt to find uniquely human cognitive attributes has failed. Oh yeah? What about the set of cognitive attribute that allows you to send a robot to Mars? Or write a philosophy book?* Although there are certainly many similarities between humans and nonhuman animals, I just don’t take seriously anyone who denies the obvious and vast differences. Robot to Mars! Seriously! For those skeptical of human uniqueness, I highly recommend Michael Gazzaniga’s excellent book Human: The Science Behind What Makes Us Unique. As evidenced by practically everything in our culture as well as particular neural structures/functions, we are not just different by degree, but in kind. And even if it was just in degree, the level of difference in degree is of such magnitude it stills warrants the conclusion of human cognitive uniqueness. See this post for more.
So yeah, imo, the AMC has so many problematic premises it can barely even get off the ground as a convincing argument.
*Edit: I’ve realized that someone might wonder why the ability to send a robot to Mars is morally relevant. I don’t think it is. But the type of creature capable of sending a robot to Mars is also probably capable of moral deliberation and reflection, which certainly seems to me like a candidate capacity for bestowing moral worth. But since I do in fact place some value on basic organic sentience, clearly moral reflection is not the source of all of human worth, but I do think it grounds the majority of human worth. In fact, I think moral reflection (which is a skill enables by reflective consciousness) is of such importance than it generates moral value in terms of the counterfactuals for biological potential.