I think examining the evolution of consciousness in animals helps shed light on it in humans. Admittedly, there are difficulties. Animals can’t self report using language, which limits just how much of their experience can be garnered from experiments. Still, taking data from human studies and combining it with animal studies can provide a lot of insight.
One issue is that, in the absence of a precise definition of “consciousness”, there is no sharp line in evolution where everyone agrees that consciousness begins. Scientists, such as Joseph LeDoux, who seems inclined toward animal consciousness minimalism, and Antonio Damasio, who’s more inclined to see it as widespread, can agree on all the relevant facts, but disagree on how to interpret them.
This leads many of us to come up with hierarchies. Those of you who’ve known me a while know mine:
- Reflexes and fixed action patterns
- Perceptions, representations of the environment, expanding the scope of what the reflexes are reacting to
- Volition, goal directed behavior, allowing or inhibiting reflexes based on simple valenced cause and effect predictions
- Deliberative imagination, sensory-action scenario simulations assessed on valenced reactions
- Introspection, recursive metacognition and symbolic thought
1 seems to apply to all living things, 2 to many animals, 3 to at least mammals and birds, and 4 to the more intelligent species, with 5, at least at present, only appearing to exist in humans.
But I’m far from the only one who’s come up with a hierarchy. I highlighted LeDoux’s a while back. Indeed, it appears to be an ancient tradition going back at least to Aristotle. The ancient Greeks didn’t have a word for “consciousness”, but they did write about the soul.
(The Greek word for “soul” is “psyche”, which obviously is where we get the term “psychology” from, but its etymology is interesting. It originally meant “to breath”, what probably seemed like the primary difference between living and non-living things.)
Plato’s conception of the soul was something immaterial that survived death, which resonates with the conception in many religions. Indeed, the word “soul” today is largely synonymous with the immortal soul of monotheistic theology. A lot of the way the word “consciousness” is thrown around today seems like an unwitting code word for this version of the soul.
Aristotle’s conception was more materialistic. Most people take him to regard the soul as part of the body and mortal. (Although, per Wikipedia, there is apparently some controversy about it.) And he had his own hierarchy back there in the 300s BC.
- The Nutritive Soul, enabling reproduction and growth
- The Sensitive Soul, enabling movement and sensation
- The Rational Soul, enabling reason and reflection
1 was labeled the “Vegetative” soul in the Wikipedia article on soul; it appears to apply to all living things. 2 applies to all animals. 3 is supposed to apply only to humans.
When I first read about this hierarchy years ago, it didn’t really work for me. My issue is that many animals appear to be able to reason to at least some degree. While debatable for fish, amphibians, or arthropods, all mammals and birds appear able to think through options and do short term planning. This seemed like yet another trait taken as unique to humans but where the real difference is a matter of degree rather than any qualitative break. Indeed, my thinking is that consciousness, if equated with baseline sentience, requires at least an incipient ability to reason.
However, I’m slowly making my way through Simona Ginsburg and Eva Jablonka’s The Evolution of the Sensitive Soul (which I was alerted to by Eric Schwitzgebel’s review). Obviously the title refers to Aristotle’s hierarchy, and the goal is to explain what the author’s call “minimal consciousness”, which they note is often referred to as “primary consciousness”, among other names.
And they equate minimal consciousness, sentience, with the sensitive soul. However, they don’t exclude all reasoning from the sensitive soul. (Indeed, their unlimited associative learning thesis, as I understand it, will require that it be there, but I haven’t reached that part of the book yet.) G&J draw the line at symbolic reasoning, involving language, mathematics, art, etc. That makes the rational soul equivalent to my own level 5 above.
I haven’t read Aristotle directly, so I don’t know if G&J’s characterization is closer than Wikipedia’s version. And I’m not sure “rational soul” is the most accurate way to describe it. And the sensitive soul itself has vastly varying capabilities across species. But minds, both animal and human, are complex things, and trying to boil down the difference to a single phrase is a lost cause anyway.
So, in this framework, all living things, including plants and simple animals, have a nutritive soul, many animals (but not all) have a sensitive soul, and humans a rational soul. G&J’s goals is to explain the sensitive soul.
What do you think of Aristotle’s hierarchy? Or G&J’s interpretation of it? I’m still inclined to use my own more detailed hierarchy (which admittedly still vastly oversimplifies things), but is Aristotle’s easier to follow?
28 thoughts on “The sensitive soul and the rational soul”
I tend to feel the way you do about animal consciousness and I tend toward Aristotle’s view of soul as the essence of a being, though mortal. I don’t believe a soul survives the death of the body. I don’t want to go all mushy on you, but I also believe some animals also possess a soul: my boxer, Daisy. Ok, I’ll go a little mushy: I don’t believe I could love someone or something that didn’t have a soul and I don’t believe anything without a soul can love anything else. I also believe some dogs possess rationality. Daisy’s behavior is mostly rational but sometimes seems irrational to me. Her behavior is rational in that it seems logically consistent with a set of axioms I have intuited that she behaves in accordance with, like barking at other dogs and workers who smell “funny” or wear yellow jackets, protecting my wife and me, allowing the little ones to do whatever they want to her as long as it’s within limits, backing away from me when I come to pick her up and put her in the back of our car to drive to the vet’s, etc. Incidentally, when she sees herself in the mirror, she does not bark at the dog she sees. She behaves irrationally though, when it’s time for me to take her for a walk she runs around the table making me chase her to put the halter and leash on her, even though she wants and needs to go out.
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That’s the thing about dogs — they’re primarily emotional beings. Their excitement overrides any thinking. (Some of the most fun dog show footage is of highly trained and highly prepared dogs just losing it and going crazy having fun in the ring. To the embarrassment (and often secret entertainment) of their handlers. 😀 )
In the sense you describe, I think animals have souls too. And I agree dogs do have some rationality, within the scope available to them. It might be in just figuring out the best path to a piece of food, but it’s there.
As to your dog behaving irrationally, hey, humans do plenty of that too. We’re all subject to letting our emotions overrule the more rational aspects of our mind.
First, what animals don’t have a sensitive soul?
Second, I think Aristotle’s hierarchy misses the essence of “soul” when he doesn’t apply
“sensitivity” to plants. I’ll be interested to see how G&J treat plants.
Finally, my hierarchy, just because, still in development:
1. Input —> [neumenon] —> Output
(existence, Output contains Mutual Information, Aristotle’s material/efficient/formal causes, panpsychism)
2. Input —>[cybernetic system] —> Output
(Output approaches a goal state, so, GOALS. Cybernetic systems include things like tornadoes, lightning, rivers, etc.)
3. Input —>[cybernetic system]—> [functional mechanism]:
Input —>[functional mechanism]—>Output
(Output of mechanism approaches GOAL of cybernetic system (Aristotle’s final cause), so has the “function” of moving some state toward goal state. Natural Selection is the paradigm “functional mechanism”-producing cybernetic system. Functionalism. Mike’s Level 1.)
4. Environmental Input—>[functional mechanism]—>representation
Representation —> [functional mechanism] —> Output
(The GOAL of the representing mechanism is to generate a vehicle having significant Mutual Information with respect to some feature in the causal history of the environmental input. The goal of the responding mechanism is to generate a response which is valuable (to cybernetic system) relative to the target of the Mutual Information. Representationalism. Mike’s Level 2.)
5. Multiple representations —> [unitracker] —> combined representation
(The combined representation has some Mutual Information relative to each input representation, but more importantly, has strong M.I. relative to the unitracker itself, and therefore to the pattern which the unitracker is tracking, which may or may not be associated with an environmental thing. Integrated Information Theory (sorta).)
6. Multiple combined representations —>[semantic pointer mechanism]—>representation to multiple mechanisms
(Semantic pointer mechanism is capable of generating unique representations relative to one or a few input representations out of a very large number (millions+) of potential inputs. Attention mechanisms determine which are the effective input representations. Attention Schema Theory. Global Workspace Theory. Mike’s Level 3? )
7. Combined representations —> [mechanism?] —>[unitracker]
(New or altered unitracker tracking the pattern associated (via Mutual Information) with input representations. Higher Order Thought Theories(?). Mike’s Level 4?)
7b. Same as 7, except allowed combinations of inputs is essentially arbitrary.
(Aristotle’s Rational Soul. Mike’s Level 5? Any theory that says Consciousness is uniquely human.)
[new slogan: No Representation without Mutual Information)
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“First, what animals don’t have a sensitive soul?”
Aristotle would argue that they all do. But if we’re going to equate it with minimal sentience, then I think a case can be made that starfish, sponges, roundworms, jellyfish, leechs, etc, don’t have it.
“I’ll be interested to see how G&J treat plants.”
They don’t see plants as conscious, but they seem okay with labeling them as having a nutritive soul.
Summarizing a hierarchy is tough. (As I discover every time I write mine.) Yours seems to have a lot of components. Have you considered doing a blog post or two on it?
Ahhh, it’s pretty obvious that cats don’t have sensitive souls.
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Cats are plenty sensitive…to their own needs. 🙂
There’s a good book yet to be written on the psychology of cat lovers. The often seeming indifference of the animal is what most endears us to them.
Cats have too many sharp pointy bits for my taste. Every cat owner I’ve known has at some point been attacked by their cat(s). No cat I owned would outlive that.
I’ll take a cranky pitbull over any cat. One can come to an understanding with a dog.
As a rough approximation I think Aristotle nailed it. What you’re seeing as rationality in animals can be seen as just intelligence — the ability to understand, figure out simple things, and make simple plans. There is a vast gap between that and human rationality when you consider our language, our music, our art, our literature, our science, etc.
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Language, music, art, literature, science, etc, are all examples of symbolic reasoning, so I think we’re on the same page. Without symbolic thought, animals are limited in what they can reason about, but I think a rat figuring its way through a maze is engaging in simple reasoning, although if you have another useful label for it, I’m game.
I suppose we could differentiate between concrete and abstract reasoning. It’s abstraction that’s behind symbolic thinking. Various animals show the ability to think about concrete things, in a few cases with some sophistication.
But only humans seem to have abstract thought. It’s the basis of language and mathematics and a lot else.
I agree that abstract thinking is an important foundation for symbolic thought. But I think that’s another case of degrees. Studies like this one seem to show abstract thinking goes pretty far back. (Admittedly, this could be another case of what we want to call “abstract”.)
A number of studies have shown animals have some facility with numbers in concrete form — with the natural numbers with small counts. Even humans seem to have the ability to recognize and categorize groups up to about seven. We can recognize without counting that four apples is less than five apples.
That’s a very concrete grasp of the natural numbers and the most basic (concrete) math principles. Human brains take it to an entirely different level.
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“Once the animals no longer need to fear each other, they fall into a daze and take on that dumbfounded look they have in zoos. Individuals and nations would afford the same spectacle if some day they managed to live in harmony, no longer trembling openly or in secret.” (Cioran)
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Not familiar with Cioran, but he sounds pretty pessimistic.
I like Mike’s hierarchy, elegantly capturing major capabilities that people care about when they talk about minds and consciousness. Mike’s category 4 is an important distinction along the road from Aristotle’s sensitive soul to rational soul. People often wrongly deny animals the abilities in 4 on the ground that the animals lack those in 5.
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Thanks Paul! An interesting question is how widespread 4 is among animals. I’ve seen estimates ranging from only humans, to primates, to intelligent mammals, to all mammals, birds, and reptiles. I suspect there’s no clean break between 3 and 4, but a spectrum between them.
As we consider consciousness in light of Covid-19 and our response to it, let us ask this question: if each of us had the power and permission to eliminate one other person each week, how many people would exist before we all agreed to stop? Let this be a measure of consciousness’ value. (Be it known that this occurred to me as I sat slack-jawed before the spectacle of a certain Speaker of the House.)
Consciousness certainly gives us the ability to wish people away, not that it’s a productive activity, particularly since, in politics, one person’s villain is another’s hero.
Ah hah! I’ve been falling behind on my own blog reading so I just found this. I’ll mention your hierarchy when I get to mine. And I see now which book you are reading about the evolution of consciousness. I hope you put some more thoughts on that book here when you finish it.
I don’t have coherent thoughts yet on your hierarchy just yet. I need to spend some time writing and integrating a few things from all my notes. Two things in particular are important:
First, you just saw my post on Dennett showing his thoughts on the cultural evolution of language in a few basic steps (synanthropic words, domesticated words, coined words, technical words). I think there are implications for a consciousness hierarchy here.
The other thing I’m paying attention to are the steps identified in Evolutionary Epistemology. In a recent article I published, I noted that Donald Campbell (who coined the term EE)….”settled on a 10-step outline that showed the broad categories of mechanisms that biological life has used to gain knowledge. This starts with the earliest origins of life where problems were solved over generations through mere genetic variance alone, without any aids from motion or the formation of memories. This earliest slow accrual of genetic knowledge eventually led, according to Campbell, to the other mechanisms: movement, habit, instinct, visually-supported decisions, memory-supported decisions, observational learning from social interactions, language, cultural transmissions, and finally, scientific accumulations of knowledge.” I think these steps would naturally correlate with steps of consciousness too, just with different labels.
Still thinking, but thought you’d like to chew on these too.
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Thanks Ed! Definitely you’ll see my thoughts on the book here. I’ve just finished the first part, which was a pretty wide ranging survey on the history of research into consciousness. I’m just now getting into the meat. That said, this book is something of a slog. The writing style of the authors is highly jargon filled. Much of it I’m familiar with, but it’s thick enough to make it a slow read.
On hierarchies, one thing I try to be clear about is mine is not meant to be any kind of new theory. It’s really just a sort of pedagogical tool and mental crutch I came up with, initially in response to naturalistic panpsychism or other highly liberal views of the distribution of consciousness. It relates various definitions of consciousness that people hold, from liberal to the most narrow.
I usually find myself agreeing with Dennett. And I do think his hierarchy has a lot going for it. (He also has others, such as the Darwinian, Skinnerian, Popperian, Gregorian one. Which is fine. I have multiple myself. There’s no reason to insist there’s only one true one.) But I’m a little nervous about his views on the relationship between consciousness and language. He seems to endorse the idea that thought requires language, which has never struck me as plausible.
Campbell’s views sound interesting. Is that on your blog, or do you have a link to the article?
Keep thinking! I’ve been reading about consciousness for several years now, and I’m still learning new things.
I don’t think this particular hierarchy works for me.
For one thing, humans are animals but animals are not plants, but to say they have something in common is just saying plants and animals are both alive. Of course, that is true but I’m not sure that puts the two logically in some sort of hierarchy relating to souls or consciousness. It also seems to be trying to set humans apart from the rest of nature. Consciousness evolved from animals with the evolution of the bilaterian body that enabled movement. Movement required an internal mapping and memory of the external world so this development coincides with the first primitive “brains” and nervous systems.
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To elaborate a little more. Plants and animals aren’t really in a hierarchy. They are divergent evolutionary paths based primarily on their energy systems and the efficiency of the systems. Plants are based on sunlight and chlorophyll. Animals are based on plants either directly by consuming plants or indirectly by consuming animals that eat plants. Plants are low energy (maybe even “sleepy” :)) whereas animals have a more high energy capability, which they need to support movement and their nervous systems.
Aristotle obviously didn’t know about evolution. (Although he reportedly had some good guesses in the right direction.) If he had, I suspect he would have said that the nutritive soul applies to unicellular organisms, including the common ancestors of plants and animals. Of course, that does largely make the nutritive soul a synonym for biological life, risking evoking vestiges of vitalism if we take it too seriously.