This is syntactically a little awkward, but my question is:

Is there some objective sense in which the differences, taken in sum, between humans and other animals are greater than the differences between any two non-human species?

For instance, you may say that humans are smarter, but doesn't this assume intelligence is somehow preferentially "weighted" in your calculation of the "distance" between species? Presumably the "human exceptionalist" thinks brain-size is more important than, say, neck-length.

Is this preference or any other argument for human exceptionalism justified without reference to distinctly human values?

  • 3
    The weight we place on intelligence, necklength, or any other property depends on what problem we're trying to solve. If the problem is to develop standards for ethical behavior, then there's at least an argument that sentience (which is related to, but not identical with intelligence) is the key property, because "harm" caused to a non-sentient being is (by definition) not experienced, and hence not really harm.
    – WillO
    Commented Jul 21, 2014 at 14:02
  • Presumably the "human exceptionalist" thinks brain-size is more important than, say, neck-length. - I'm no biologist but I think that the brain-to-body mass ratio is what's important here.
    – user132181
    Commented Jul 22, 2014 at 0:25
  • 1
    @WillO I take your point, but it seems to me to be begging the question. Of course humans are better than non-humans at conforming to human standards of behavior. But maybe this would lead us into a debate about moral realism which I'm neither prepared nor qualified to have :) Commented Jul 22, 2014 at 5:43

4 Answers 4


Of course there are significant, objective differences between humans and other animals. One of the most obvious is our capacity for language. Another, as Dave pointed out, is our visible impact on the planet. But then, there are significant, objective differences between animals of all kinds. The differences aren't hard to find, the question is whether those differences make humans not just qualitatively different from other animals, but better.

It's certainly possible to make that argument. For example, you could argue that our ability to analyze and discuss our own behavior makes us uniquely responsible for that behavior, and hence places us in a superior ethical category from other animals. How much of that argument you accept probably depends on the extent to which you believe animals are sentient--the more conscious an animal is, the more like a human they would be along this axis, and hence the less exceptional humans would be. It might also depend on the extent to which you think "ethical responsibility" is a well-formed concept in the first place--in fact, there are dozens of rabbit-holes you could dive into following (or rejecting) this line of argument.

In general, you will always have difficulty drawing ethical conclusions from objective observations--this is known as the is-ought problem. However, there are definitely plenty of objective differences you could use as starting points in arguing for human exceptionalism.

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    +1 I would imagine it also depends on whether you regard human morality as exceptional among the ways in which all species regulate the social behavior of their members. Commented Jul 21, 2014 at 22:15
  • It has not been established positively that only humans have language - how could we possibly make such a claim without observing and understanding the reasoning behind every action an animal makes, since there are so many other possible modes of communication? We are also not the only species with such a wide impact - try grass, or algae. Last, there is a lot of work to be done to even establish the idea of ethical responsibility. -1
    – commando
    Commented Nov 21, 2015 at 3:53
  • @commando I never said that only humans have language, I said that our capacity for language exhibits clear objective differences from that of other animals, as the Wikipedia article I linked explains. Second, no other single species has had the same kind of impact on the planet as humans, not even grass or algae. Plants can and have changed the composition of the atmosphere, for example, but humans are currently doing so orders of magnitude faster. Finally, I never asserted the existence of ethical responsibility, only noted it as one possible argument for human exceptionalism.
    – Malcolm
    Commented Dec 23, 2015 at 18:40
  • @commando (I've edited my answer to make explicit my reference to the is-ought problem, as well as adding a link. Hopefully that clarifies my argument with regards to your last point.)
    – Malcolm
    Commented Dec 23, 2015 at 19:09
  • @Malcolm the wiki is out of date (refs Deacon 1997, my god). and begging the question. The original Deacon article literally just states uniqueness of human language as fact with no evidence. So that's vacuous. The claim of uniqueness in terms of recursion is plainly false and out of date, attributable to Noam Chomsky thinking he knows what he's talking about: see Gentner et al 2006 for evidence of recursion in birdsong. The last claim, referring to Trask 1999, is simply irresponsible and impossible to support without knowing what all animal communicative behaviours do.
    – commando
    Commented Dec 25, 2015 at 1:19

Humans are the only animal (thus far) with the potential to enable life (as evolved on Earth anyway) to escape the death of our sun.


I am unaware of any animal species that has had such a wide spread and numerous population, and had such a significant impact on the environment (paving roads, building buildings, draining swamps, daming rivers, as well as what are usually thought of as "environmental impacts" of waste/sewage). There is essentially no place on Earth where you can go without finding some impact, especially trash, from humans.

Arguments could be made that large scale evolutionary shifts, like

  • the development of photosynthesis and aerobic respiration, or
  • the transition of animal life from ocean to sea

are larger impacts, but (in hindsight) these transitions did not seem to be focused on the characteristics of a single species.

  • +1 This is an excellent point: the "anthropocene." I'd be interested to know if any paleo-biologists could think of a species that rivals humanity in this respect. Maybe I'll ask that over at biology stack exchange. Commented Jul 21, 2014 at 22:21
  • -1 see my comments on Malcom's answer above, this sort of exceptionalism begs the question.
    – commando
    Commented Dec 25, 2015 at 21:30
  • @commando I'm unsure what would qualify as "exceptional" to you. I believe that we are pretty clear outliers in the direction of "single species that have global environmental impacts", and it is not the case that selecting a particular feature for consideration constitutes begging the question.
    – Dave
    Commented Dec 26, 2015 at 3:36

Some values are not anthropocentric. I'm going to start with Karl Popper's epistemology. Popper points out that some knowledge is objective, it is instantiated in things other than human brains like books, computer programs, e-mails and so on, which means it can be criticised by others. According to Popper all knowledge is created by conjecture and criticism and can't be created in any other way. (In particular, it is not justified in any way.) If there were non-human aliens creating knowledge they, too, would have to create it by conjecture and criticism. As a result any thing that wants to create knowledge would have to adopt ideas that many people don't have, like the idea that you should answer criticism instead of ignoring it. This just leaves the question of whether there is some non-anthropocentric reason to favour the growth of knowledge. Imagine that there aliens or AIs or some other non-human thinking beings. We would have some disagreements with them and we would have to create knowledge about how to resolve such disagreements.

See "The Beginning of Infinity" by David Deutsch for arguments about connections between morality and epistemology and explanations about why rationality and science are not anthropocentric. For Popper's epistemology, see Chapter I of "Realism and the Aim of Science". For Popper's ideas on ethics see "Toleration and Intellectual Responsibility" by Karl Popper http://universaltolerance.org/articles/Toleration%20and%20Intellectual%20Responsibility%20%20Sir%20Karl%20Popper%20%20.pdf



and references therein.

Animals lack the ability to create new explanatory knowledge, unlike people. As a result there is a qualitative difference between animals and humans in that an animal can never make a contribution to the growth of objective knowledge in its own right. Dogs never learn to write, they don't learn English beyond some short list of commands, they can't write music or program computers. The reason is that a dog has a finite bag of tricks written into its genes and when it exhausts that bag of tricks it can't create anything new. Other animals are in the same position. For example, experiments in trying to teach apes language always reach a point where the ape can't do anything more sophisticated than what it already does. See "Kanzi: The Ape at the Brink of the Human Mind" by Sue Savage-Rumbaugh and Roger Lewin for an example. (See also "The Beginning of Infinity", Chapters 15 and 16.)

The animal has a particular set of knowledge (in the sense of useful or explanatory information) in its genes. So any copy of the relevant genes will have the same knowledge and no individual animal matters very much. By contrast, each person has a unique set of ideas and habits instantiated in his brain and that does matter. Every time a person dies unique ideas are destroyed that might lead to progress. Every time you mistreat a person you make it more difficult to get access to any good ideas he might have or that he might develop.

You might say that animals can suffer and so this provides another kind of value and that this value is not limited to humans.

An animal can't understand what is happening to it and so can't interpret the pain as being bad. The idea that something is bad is a sophisticated interpretation of experiences that only arises in the light of a lot of knowledge. For example, one reason people suffer is that they can imagine all the stuff they won't be able to do as a result of injury or death, unlike animals. Animals are robots programmed to propagate genes. To do this, genes program their vehicles to move away from stuff that will damage the vehicle, refrain from using damaged body parts so they can heal, signal danger to relatives and other stuff like that. They bear more resemblance to characters in a computer game than to people.

You might say that it looks like animals suffer, but that is an interpretation of what you see when you look at an injured animal. The explanation I have given criticises that interpretation. Likewise when you say an animal has a brain structure that is similar to some human brain structure you are imposing a false interpretation of what is going on. Both the human brain and the animal brain are universal computers: they can do anything that a universal Turing machine can do. It follows that you can't tell exactly what it is doing just by looking at the hardware. To the extent that some part of the animal's brain is similar to a person's brain it is participating in a very different process. The computation in the animal's brain doesn't involve understanding what is happening to it or anticipating problems as a result of an injury or anything like that: the animal doesn't suffer.

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    Some good material in the first half, but the part about animals not suffering ignores the last couple centuries of study of human and animal differences and similarities. All evidence from autonomic reactions to learning paradigms to physiological similarity to associated symptoms like PTSD indicate that pain is painful to animals even if they don't reflect linguistically on the suffering like humans do.
    – Rex Kerr
    Commented Jul 21, 2014 at 18:23
  • I don't ignore them. "Autonomic reactions" are reactions below the conscious level, i.e. - not suffering. "Learning paradigms" animals don't learn as I explained. "Physiological similarity to associated symptoms" is not relevant. What matters is whether the animal's brain instantiates the relevant abstraction. Information that would produce suffering if it were part of a process that creates new explanatory knowledge that can anticipate problems does not do so if it is not part of such a process.
    – alanf
    Commented Jul 22, 2014 at 9:31
  • Animals learn all the time. They don't have any declarative learning using language because they don't have language, but they do single-trial learning, conditioned avoidance, association (hi, Skinner!), etc. etc.. Also, when you stub your toe, is it unpleasant because you are thinking, "Ah! Alas! Verily, this may hamper my ability to run at speed, and though I had not planned to do so I sorely miss the option!", or are you thinking "OW! That hurts! I don't like it! It's painful and distracting and I wish it would stop!" All that latter stuff is well within the reach of many animals.
    – Rex Kerr
    Commented Jul 22, 2014 at 18:18
  • there are many machines you can buy that can be programmed to automatically perform certain tasks, e.g. - CNC milling machines. Those machines don't learn anything in the sense of creating explanatory knowledge. No CNC milling machine ever learns to do anything apart from a finite repertoire of tasks allowed for in its programming. The same is true of animals. No animal ever learns musical composition or physics or even how to hold down a job in Starbucks.
    – alanf
    Commented Jul 22, 2014 at 19:41
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    @alanf The same is absolutely NOT true of animals, as any animal trainer can trivially demonstrate. Language and abstraction are not necessary for learning, unless you are using a different definition of "learning" than literally every professional in the field.
    – Malcolm
    Commented Jul 22, 2014 at 20:01

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