Max Horkheimer's 1947 book The Eclipse of Reason argued that over the course of history, the conception of reason shifted from the objective - the Greek idea that reason qua logos governs the Cosmos - to the modern, instrumental concept of reason.

He depicts the 'instrumentalisation of reason' as a prime characteristic of the modern era, referring to the use of reason as a means to achieve specific ends or goals, rather than as an end in itself. This type of reason is deployed with a focus on efficiency and utility, and it is often used to solve practical problems or to achieve specific objectives. Instrumental reason can be contrasted with the traditional attitude of 'substantive reason,' which involves the use of reason to explore and understand the world in a more comprehensive and holistic way. (Recall the the original meaning of 'cosmos' was 'an ordered whole'.)

Parallel to this shift towards instrumental reason is the general rejection of telos (action towards an end) in modern philosophy since Galileo.

In regards to evolution in particular, the concept of 'purpose' is not applicable, as evolution does not occur in respect of a specific goal or end. Rather, evolution is a natural process that occurs through the interaction of random genetic variation and the selection pressures of the environment. This means that the traits and characteristics of organisms are not imbued with any particular purpose other than procreation and survival, governed by the process of natural selection.

In this you can see the rejection of the idea of 'reason' in the Aristotelian sense of 'final causation' or telos. The very idea that life could be governed by reason, or that there is any reason for the existence of life, becomes meaningless. (Richard Dawkins, when asked in a TV panel session, if there is a reason for life to exist, said that 'you're playing with the word "why" there'.)

But the specific question I want to ask here is, against this background, does this imply that humans (or equivalent extra-terrestrial species) are the only rational actors in the cosmos? That humans are the only beings capable of action towards an end, because they alone are able to bring instrumental reason to bear on the solution of problems? It seems a clear implication of this aspect of modern thought.

And the further implication of this is that humanity's use of reason is disjunctive from the cosmos as a whole, that it is somehow 'internal' to the minds of rational actors and not intrinsic to the world as such.

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    Brentano identified intentionality as the mark of mental phenomenon, while Heidegger identified it with care and Sartre identified it with consciousness, Chisholm identified it with psychological aspect of language... Dec 27, 2022 at 1:26
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    Sorry, I'm having trouble reading your wall of text. My cat is intentionally trying to get my dinner, and I have to keep pushing him away.
    – BillOnne
    Dec 27, 2022 at 1:31
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    I'd say there's a difference in degree and not type in re distinguishing humans from the rest of the animal kingdom. Aristotle defined humans as rational animals and we followed suit (h. sapiens). That was 2.5k years ago when, not to insult Aristotle's intelligence, everything appeared clear-cut, every class of object fit snugly into its own box. As time went by we encountered the fuzziness of the world which thwarts any attempt to separate stuff into crisp categories. We're left then to put animals, including humans, on a spectrum with respect to abilities
    – Hudjefa
    Dec 27, 2022 at 6:04
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    I guess it highly depends on how we define "rational", but animals have been shown to solve puzzles for food or use tools. In my book that would be a demonstration of intentional and rational action from a non human.
    – armand
    Dec 27, 2022 at 6:27
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    @Agent Smith There is plainly a difference in kind between h. sapiens and other animals, one that is so clear that if you think the difference is not worth debating, then it's probably not worth debating!
    – Wayfarer
    Dec 27, 2022 at 7:33

3 Answers 3


Long story short

This is evidently false. As it is discussed whether great apes can work towards shared ends, it is quite obvious that intentionality is seen as a given. Some animals can utilise objects and fellow animals and they can even learn and use symbols as expression of meaning and manipulate them (ie. use language and logic). Saying that this behaviour is categorically different from rationality is a bold statement. Instrumental reason is certainly a thing for some animals. Humans are animals, after all.

Long answer

Many species, including dolphins, great apes, and crows have proven that they act with intention time and again. Crows have shown to consider how their behaviour will affect the behaviour of their fellow crows so that they actively manipulate other crows with their behaviour to achieve their goals. These are so-called second-order dispositions and they mean that they are conscious of how their behaviour will affect the world and other crows. Already as early as 1917, a guy named Krüger showed that chimpanzees can identify and manipulate objects so that they help them to achieve a goal.

It is not exactly far-fetched to say that at least some species thus are able to imbue objects (and fellow animals) with a telos, ie. make them serve a role in achieving their goal.

Chimpanzees and even goats have shown to be able to learn, use, and in some cases even manipulate symbols according to rules (ie. use language and logic). Who are we to say that all this has nothing to do with rationality?

There even are doubts that agreeing upon and working towards a common goal is unique to humans. Tomasello calls this shared intentionality and claims that this was unique to humans but there are serious doubts (1, 2) that this claim can be upheld.

Therefore, the more reasonable claim is not that there is a categorical difference in cognitive abilities between us and animals but that the scale on which we are able to use and especially combine cognitive abilities seems to be unique. This fits much better with scientific findings on brain physiology and evolution as well.

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    Would pack hunting (wolves) qualify as shared intentionality?
    – user59124
    Dec 26, 2022 at 23:15
  • So, you broaden the scope of reason to allow that other sentient creatures, such as apes, and wolves are imbued with it. However this doesn't seem to allow for the type of rational reflection that is open to humans in particular. It deflates the question rather than addressing it.
    – Wayfarer
    Dec 26, 2022 at 23:16
  • Notice also the description 'rational actors'. Certainly many creatures, arguably all creatures, act intentionally in accordance with the imperatives of survival, but humans alone are capable of reflecting in the abstract, so far as we know. (Incidentally, the fact that living beings activities are intentional is the reason for the neologism 'teleonomy' to describe their apparent purposefulness en.wikipedia.org/wiki/Teleonomy)
    – Wayfarer
    Dec 26, 2022 at 23:25
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    @Wayfarer Look, I'm just telling you how the literature uses intentionality. No, wolves do not qualify, as shared intentionality is much more complex than you want to make it. Also, rationality is so ill-defined a concept that it does not seem to be useful at all. Instead, I'd advise you to read on shared intentionality before making such sweeping statements. Otherwise, you look like someone who has already made up their mind.
    – Philip Klöcking
    Dec 27, 2022 at 0:15
  • The question concerned 'rational actors' - actors capable of rational intent. And the fact that rationality, or reason, is not easily defined, doesn't mean it ought to be simply discarded.
    – Wayfarer
    Dec 27, 2022 at 1:24

You seem to have answered your own question, judging by your comments in which you state that human ability to act with rational intent is in a different class to that of, say, dolphins. If by rational actors you mean beings capable of performing the kind of rationally intentional acts that only humans seem to perform, then yes, humans are the only rational actors we know of in the cosmos. That said, our ability to act rationally seems to have come about through evolution, and the cosmos is a big place, so there may well be other rational actors in other parts of it whom we will never get to meet. And if, as some do, you find it necessary to believe in an infinite number of universes to explain why there is no 'collapse' of quantum mechanical wave functions, then I suppose the probability of there being other rational actors goes up accordingly. (Incidentally, that some humans believe fervently in the multiverse just goes to show that we might be the only irrational actors too.)

As for your final comment about human use of reason being 'disjunctive' from the Cosmos etc, the truth of the sentence depends on exactly what meaning one decides to put upon the words you have written. Certainly if all humans left the earth and went to live on Mars, rational acting would no longer be a feature of the Earth, at least until some other class of animal evolved to fill that particular gap we had left.

  • "our ability to act rationally seems to have come about through evolution" - however, I wonder if the theory of evolution, which is after all concerned chiefly with biology, really provides an account of the faculty of reason. It seems to me if you try and account for reason simply in terms of a biolotical adaptation, then you're undercutting the rational basis of for such judgements. This is, of course, the basis of the 'argument from reason', as advocated by Alvin Plantinga, and in a less religious register by Thomas Nagel.
    – Wayfarer
    Dec 27, 2022 at 9:10
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    @Wayfarer what grounds do you have for supposing that the faculty of reason does not have a biological origin? It seems to me to be quite clear that the faculty is associated with the brain, which is biological and which appears to have evolved. Granted we don't yet have a proper explanation of consciousness, but all the signs point to consciousness being somehow associated with brain activity, aka biological activity. Dec 27, 2022 at 10:41
  • There are alternatives to brain-mind identity theory and biological reductionism. Here's a discussion from Thomas Nagel tiny.one/2p8szys5
    – Wayfarer
    Dec 27, 2022 at 20:59
  • @Wayfarer it was very kind of you to give the link to Nagel's paper; however, I found that his observations amounted to a doubt about brain-mind identity and biological reductionism, not an alternative theory (he explicitly admits in the paper that he does not have all the answers). I take the view that the brain and the mind are linked in some way- at the very least, the brain is necessary for the mind to function. I also think it is obvious that brains have evolved... Dec 27, 2022 at 21:35
  • ...but I am clear that we have no explanation of the cause of consciousness, and so we cannot know whether consciousness is driven and determined by physical processes in the brain, or simply enabled by them- as if they provide an environment in which thought can happen independently of physical processes. It is also clear to me that the scope of human thought is much wider than evolutionary advantages would require it to be- but that could simply be that evolution had equipped us with general purpose mental tools and we subsequently applied them to a wider range of uses. Dec 27, 2022 at 21:53

Does it imply that humans are the only rational actors in the cosmos?


First, I think its important to define "rationality" as I interpret from the question. Rather than quibble about what is intentional or what qualities of thought define rationality and other semantic hair-splitting, we could simplify things: Human mental faculty exhibits a scope and scale beyond that of other beings whether you measure it directly or just take a qualitative glance at this question. No matter what you call it--intentionality, reason, rationality--or how you measure it, the capabilities, depth and scope of the human mind are beyond those of other living things on earth.

In the broad context of the question, we don't have to agree on how reason or rationality should be defined or how it should be measured. We can just acknowledge the existence of this unique human ability. Afterall, it'd be difficult to deny without providing evidence thereof.

I'll borrow the term used in the question and call this reason.

No other living organism is even capable of reason. How could they? It is a thing comprised of itself in the human mind. We use our reasoning to define it.

The term "disjunctive of the cosmos" is too squishy for me interpret your meaning, but I do think that reasoning is internal to humans. It's an ability given to us by our creator. In the same way that our definition of reason is borne of itself, humanity was made in God's image.

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    "It's an ability given to us by our creator" is a perfectly orthodox Christian belief, but if you believe it, then you also must believe that there is at least one other rational intentional agency, namely, God.
    – Wayfarer
    Dec 27, 2022 at 9:26
  • If human abilities only differ in scale, not in kind, ie. they are essentially the same but just much stronger expressed, your argument is void. And you do not provide a single compelling argument against that possibility.
    – Philip Klöcking
    Dec 27, 2022 at 11:53
  • They're different in kind. No other species exhibits anything like the capabilities of h sapiens along any number of axes. I suggest this is being questioned for meta-philosophical reasons, i.e. it is fundamental to naturalism not to allow for such ontological distinctions.
    – Wayfarer
    Dec 27, 2022 at 22:06

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