Speciesism is like racism or sexism a form of discrimination. A useful definition of discrimination is: Causing harm or disadvantage to an individual by making a value-laden distinction between individuals based criteria that are not morally relevant in that situation. The question is whether species boundary (or being a Homo sapiens) is a morally relevant criterion.
In our culture, all sentient humans have some basic rights, such as the right to live, the right not to be property or the right not to be used as merely means to someone else’s ends. Not all human beings have those basic rights. For example: fertilized human embryos are used and killed in stem cell research and therapy. So non-sentient humans (humans who have not yet developed the capacity to feel and have a consciousness) have less rights. According to our culture, the moral community consists of the intersection of two sets: sentient beings and human beings. We will now present 4 arguments why the species boundary is morally irrelevant and another 4 arguments why sentience is morally relevant.
Arguments against the species boundary
In order to avoid the risk of opportunism in our ethics, we should avoid adding arbitrary, farfetched or fuzzy criteria without good reasons.
1) The biological species boundary is arbitrary. Why pick out “species” in the list of biological categories? 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 speciesHomo sapiens, the subspecies Homo sapiens sapiens and the ethnic group of whites. 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 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 rights if its close relatives could have gotten fertile offspring with some other morally relevant beings. (I refer to its close relatives because the being himself could be infertile.)
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-polar bears and off course horse-donkeys (mules). If these are possible, and if the genetic distance between humans and chimpanzees is not larger than the distance between those existing interbreeding species, it is possible that humanzees can be born. What would the moral status of this hybrid human be? Will it get rights? Here too, there is an arbitrariness.
4) Species boundary refers to genes or appearance, and these are not morally relevant because there is no such a thing as an “interest gene” connected to all and only humans. Or in other words, there is no “essence” related to a species.
Arguments in favor of sentience
Each normative ethical system implies an argument for sentience. All the four arguments below have the same structure: starting with two assumptions (one fact and one value statement) one can derive that sentience is morally relevant
1) 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 good and important.
2) Welfare ethics (consequentialism) and fairness ethics (contractarianism):
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 being, but you don’t know who or what you might be. You can be a non-sentient object without well-being, or a sentient being. How would you like to be treated? Sentience will imply a different treatment.
3) Rights ethics (deontologism):
Fact: a sentient being is a being that has interests and can subjectively feel its interests.
Value: protection of interests by respecting rights is important. Note that rights are tools to protect interests. So the coupling sentience – interests – rights is not farfetched.
4) Other ethics:
Fact: a consciousness is something very complex, vulnerable and unique in the universe.
Value: We should protect and respect something vulnerable, complex or unique. Having a consciousness is something much more remarkable than having the genes of an arbitrary species.
Optical and ethical illusions
The famous Müller-Lyer optical illusion can be used as a representation of the ethical illusion of speciesism. The optical illusion (see figure below) says that our intuition judges the lower horizontal line to be longer than the upper one. This intuition is in contradiction with two other intuitions: 1) a ruler does not change length when shifted (translation invariance) and 2) the length of a line does not depend on the presence of other lines around (context independence). So one can use a ruler, or one can cover the small lines, and demonstrate that both horizontal lines are really equal. We can now do two things: abandon two of our strongest intuitions (translation invariance and context independence) and try to make a consistent geometrical system without those two principles, or one can acknowledge that our intuition about the length of the horizontal lines was wrong; it is an illusion. We prefer the latter option, because the combination of the two intuitions of translation invariance and context independence is very strong.
The horizontal lines can be interpreted as a symbol of the intrinsic values of a non-human animal and a human. The smaller lines represent morally irrelevant properties (genes of an arbitrary species, appearance,…). We might have the intuition that humans are more valuable than animals, but this intuition is in contradiction with other intuitions that are at the origin of the above eight arguments about the moral (ir)relevance of species boundary and sentience. We believe that the combination of the latter set of intuitions is stronger than the one intuition about the value of humans versus animals. So the easiest thing to do is to acknowledge that the latter is an ethical illusion.
Besides, neither the Müller-Lyer optical illusion nor the human-animal value illusion is inborn. Some indigenous people (who are not living in an environment with straight edges of houses, tables,…) are not susceptible to the optical illusion. Also the human-animal value difference is like any other ingroup-outgroup distinction a product of cultural influences. So it is fair to say that the ethical intuition about human-animal values is an ethical illusion not consistent with other stronger ethical principles such as antidiscrimination.
A more elaborated article: Speciesism as a moral illusion