In this article I will show that the human species is not a morally relevant criterion for rights and that giving humans a higher moral status than non-human sentient beings is a kind of immoral discrimination. In fact, I will give no less than 10 arguments.: 5 against the species boundary, and 5 to support the criterion of sentience. A speciesist who still wants to eat or use animals and animal products, will have a very hard time. He/she should now come up with no less then 12 arguments: 10 arguments to counter each of my 10 arguments below, one argument to show that the human species boundary is a morally relevant boundary for the moral community, and one argument to show that sentience is not a valid competing morally relevant criterion. I reward 12.000 euro for the person who is able to give those 12 valid arguments (and I mean it). If you cannot find those 12 arguments and you still consume animals and animal products, then you discriminate and you open the door for partiality, opportunism and inconsistency in your ethics.

Five arguments against the species boundary

The arguments that we are about to present, are based on moral intuitions: in order to avoid the risk of opportunism in our ethics, we should avoid adding arbitrary, artificial, farfetched or fuzzy criteria.

1) The biological species boundary is arbitrary. Why pick out “species” from the list of biological categories to which I belong? I belong to the kingdom of animals, the phylum of chordates and vertebrates, the class of mammals, the infraclass of eutheria, the order of primates, the suborder of dry-nosed primates, the infraorder of simians, the superfamily of Hominoidea, the family of great apes, the genus Homo, the species Homo sapiens, the subspecies Homo sapiens sapiens and the ethnic group of whites. There are different genetic affinities. It is arbitrary to pick out the species. Why adding this arbitrariness in our ethics?

2) The biological definition of species is very complicated and too artificial and farfetched to be used in a moral system. One of the many definitions of species refers to the possibility of interbreeding and getting fertile offspring. But why should this possibility be relevant? It is too farfetched to say that a being has a moral status if its close relatives (parents) could have gotten fertile offspring with some other morally relevant beings. (I refer to its close relatives because the individual itself could be infertile.) It is unfair that an individual gets rights because his parents are able to do something with others. It is unjust to take a principle where non-human animals simply have bad luck having the wrong parents…

Related to this is the issue of ring species such as the Larus gulls, the Ensatina salamanders or the Greenisch Warbler. Such ring species consists of different populations, whereby A can get fertile offspring with B, B with C, C with D, but D not anymore with A. Just as populations of ring species are spatially related to each other, we can say that all species in nature are temporally related in a similar way. Look at the phylogenetic tree. A modern Homo sapiens could have got fertile offspring with an ancestor, that ancestor with an older ancestor, and so moving up a branch of the philogenetic tree until we reach a common ancestor of both Homo sapiens and another species. Then we move down the branch of that other species. So there is a chain of populations connecting our species to any other species. The clue is that the higher moral status of A (a Homo sapiens) compared to D (an individual of another species) strongly depends on the fact that B and C are dead. Formulated this way, it becomes clear that such dependency on the accidental non-existence of individuals cannot be morally relevant.

3) There is a potential fuzzy boundary: it is not unlikely that a human-chimpansee hybrid (humanzee or chuman) can be born. 10% of mammal species can form interspecies hybrids. We have seen lion-leopards, lion-tigers, camel-lamas, dolphin-killer whales, sheep-goats, grizzly bear-polar bears and off course the well known horse-donkeys (mules). If these are all possible, and if the genetic distance between humans and chimpanzees is not larger than the distance between those interbreeding species, it is likely possible that humanzees can be born. What would the moral status of this hybrid being be? Also here there is an arbitrariness. And there is more arbitrariness when we look at the possibility of human-animal chimeras. A chimera is an individual composed of genetically distinct cells that originate from human and animal zygotes. The body cells of chimeras can range from 100% human to 100% non-human. Where to draw the line of humanity? What would the moral status of such chimeric individuals be? And what if Neanderthal people still existed, what moral status would they have? Or our ancestors like the Australopithecus or the Homo habilis? And what about genetically modified humans and animals? There is no objective characteristic or indicator that scientists could use to determine whether such beings should be called human and should get a high moral status.

4) The species boundary refers to genes or appearance, and these are not morally relevant, because racism and sexism where also based on genes or appearances. We should universalize the principle that genes and appearance are morally irrelevant for everyone in all situations related to basic rights violations. Also, there is no “interest gene” connected to all and only humans; there exists no uniquely human gene that generates interests in a being.

5) Belonging to a certain species instead of another is not something that we could choose, it is not something we achieved, it is beyond our responsibility, so we should not be rewarded for that. We do not deserve special treatment by having some genes. Giving a higher moral status to beings who did not chose to be born that way, is in violation of the merit principle. If we are to be rewarded, it is not because we are born in some way rather than another, but because we need things and are able to prefer things (i.e. we have a well-being).

The first three arguments indicate that there is no “essence” related to a species. Essentialism means that there are characteristics that all elements of a specific set (e.g. a species) posses and elements of other sets don’t posses. All elements of that set can be accurately described and defined by those characteristics. That specific set therefore has a single definition. Essentialism in biology is rooted in ancient philosophical thinking (e.g. Platonism), as well as major religions. In those religions it is believed that there is something special to all and only humans: all humans, and only humans, have an eternal soul, or are created to the image of God. But since Darwin, the scientific consensus says that there is nothing special about a species. It is just an arbitrary abstract classification with its limits and difficulties.

The fact that a speciesist tends to think of species as essentialized groups does not mean that there is an essence to a species. Similarly, a racist thinks of races or ethnic groups as being essentialized natural groups, even though it is now well known that there really is no essence related to an ethnic group or race. Even more: several studies give explanations for this phenomena that people rapidly (but incorrectly) tend to think in terms of essentialized groups (Gil-White, 2001, Are ethnic groups biological “species” to the human brain? Essentialism in our cognition of some social categories).

Five arguments in favor of sentience

We will now present five arguments why sentience is morally important. The reason that there are different arguments, is that there are different moral virtues (empathy, impartiality, respect) and different normative systems. Different arguments for sentience stem from these different normative ethical systems and moral virtues. All the arguments have the same structure: starting with two assumptions (one factual and one value statement) one can derive that sentience is morally relevant

1) Welfare ethics (consequentialism) and fairness ethics (contractualism). Fact: Our own well-being matters to us. Value: Impartiality is important. There is a thought experiment to check impartiality: imagine that you might be any other object or entity, but you don’t know who or what you might be. You can be a non-sentient thing without well-being, or a sentient being. How would you like to be treated? If you were non-sentient, this question would not matter to you, because nothing done to you will influence your well-being. So sentience will imply a different treatment, because well-being matters to you. This argument is nothing but the veil of ignorance of John Rawls, but applied more consistently to all entities in the universe, as was proposed by Mark Rowlands.

2) Virtue ethics and ethics of care. Fact: We can feel empathy in a meaningful way with all and only sentient beings (beings who can feel and have a well-being). Value: Developing the virtue of empathy is important.

3) Rights ethics (deontologism). Fact: A sentient being is a being that (like living beings) has interests and (unlike non-sentient living beings) can subjectively feel his/her interests. Value: Protection of interests by respecting rights is important. It is not farfetched to see a connection between rights, interests and sentience. This is at least less farfetched than making a connection between e.g. rights and the possibility of getting fertile offspring.

4) Ethics of respect and awe. Fact: Mental capacities such as consciousness are something very complex, remarkable and vulnerable in the universe. Value: We should protect and respect entities that have vulnerable and complex mental capacities. Having a consciousness is at least something much more remarkable than having the genes of an arbitrary species. Take another thought experiment: If a white person would turn into a black person, he loses one skin color but gains another; if a man would change into a woman, he loses one sexual organ but gains another; if a human would become a non-human animal, he loses some physical properties and genes, but gains others. On the other hand, if a sentient being turns into a non-sentient being, he loses something valuable and does not gain anything in return.

5) The argument from marginal cases (Dombrowski, 1997, Babies and beasts). Fact: Perceptual consciousness (sentience) is the only mental capacity that mentally disabled humans share with us. Value: Our intuition says that mentally disabled persons are to be respected because of some inherent, mental capacity that they posses. The real reason why we help them is because they can suffer. Other reasons, such as indirect rights or a slippery slope argument made by Carruthers (1992, The Animals Issue: Moral Theory in Practice), are disrespectful towards those individuals, because they deny their intrinsic value.

The above five arguments cohere with each other and indicate that sentience is a basis for moral concern and moral status. One might argue that the notion of sentience also has fuzzy boundaries, just like the notion of a species. When is a being sentient? What about invertebrates, plants,…? This is first of all a matter of fact (science). As we’ve seen, scientists do not have and will never find indicators to determine at what point a being (a hybrid, a chimera, an ancestor or a genetically modified person) should be called human. But scientists do already have quite a lot of indicators to test whether a being is sentient. And they will likely discover new indicators when they gain more knowledge about how consciousness works. Second, in our culture, non-human animals already have some moral status: look at the animal welfare laws. These laws refer to the welfare (sentience) of animals, so we already are able to use this criterion, even when there is still some scientific uncertainty about e.g. invertebrates. Third, also in human rights ethics there is scientific uncertainty about sentience: look at the discussion on abortion and stem cell research. Fertilized human egg cells are (according to scientists) not yet sentient, so they have a lower moral status in a lot of western countries. Also here we are able to deal with this scientfic uncertainty. Fourth, even if there is an inherent gradation in the levels of sentience (from simple to complex emotions), it is not really a threat to the theory, because it makes sense to couple the gradation of sentience to a gradation of moral status (see https://stijnbruers.wordpress.com/2011/12/25/the-basic-right/). All beings with a developed, complex, functioning central nervous system, all beings with a level of sentience equal or higher than those of (most) vertebrates, developed human fetuses or mentally disabled humans, have a very high moral status.