Episode 45 - Trees

Transcript

David: 0:06

Hi, I'm David Pena-Guzman,

Ellie: 0:08

and I'm Ellie Anderson. Welcome to Overthink,

David: 0:11

the podcast where two friends,

Ellie: 0:13

who are also professors,

David: 0:15

put philosophy in dialogue with the everyday.

Ellie: 0:18

Because big ideas are within everyone's reach.

David: 0:31

The planet lost an area of tree cover larger than the United Kingdom in 2020, including more than 4.2 million hectares of primary tropical forests.

Ellie: 0:43

Ah, yet another in the litany of very depressing tree statistics. There are no more old growth forests in much of the world today. And a study found that between 1900 and 2015, the entire world lost roughly a third of its old growth forest.

David: 1:02

And it seems that by the year 2030, we might only have about 10% of rain forest left. And it all is very likely to disappear in the next 100 years anyways.

Ellie: 1:17

This makes me want to go out and hug a tree.

David: 1:20

Ellie, the philosopher tree hugger.

Ellie: 1:23

No, I actually legit love tree hugging. This is about to sound super California, but my mom always encouraged me to hug trees as a kid. She loves to hug trees herself and the feeling of hugging a tree is just so wonderful. I mean, it really feels like you're hugging another being, right. I mean, you-

David: 1:44

Well, you are hugging another being.

Ellie: 1:47

I know. But I feel like tree hugging gets a bad rap, just like seen as some weird anthropomorphic thing we do, but it's so comforting and so energetic.

David: 1:56

Okay, well, so I'm obviously a very bad environmentalist because I don't really have a memory of hugging trees. And I don't think, I mean, I don't think I've done it nor do I have any particular interest. I want to protect trees and I want them to live long happy lives, but I don't feel I need to hug them.

Ellie: 2:17

Well, I actually think that there can be a connection between wanting to protect trees and hugging them because yeah, tree hugging has a stereotype around it, of like the hippie who just goes out and hugs a tree. But it actually was behind a major environmental movement in the 1970s called the Chipko movement in India, where a group of indigenous women protected trees from being cut down by hugging them.

David: 2:41

Yeah. I- and I mean, that has now become a pretty common activist strategy for the protection of forests, especially those- yeah, chaining yourself to trees, chaining your friends to trees, chaining your podcast co-host to trees, to protect the environment. But even though I, I don't have, tree hugging gene inside me.

Ellie: 3:03

You would've had to grow up in California for that.

David: 3:06

Yes, you have to have a California parents. I do have very powerful memories of trees that have had great meaning in my life and especially in my childhood and teenage years. One of them was the avocado tree that grew in my house as a child in Mexico. It was a gigantic, three to four stories, high avocado tree that grew over- well, maybe two or three stories high, but I was a child, so it was four stories high. And it grew over our kitchen and it would drop avocados onto our kitchen roof, which then would roll down onto the front door of the kitchen. So there was always an overabundance of avocados at our kitchen door.

Ellie: 3:51

You just wake up in the morning, walk outside and be surrounded by perfectly ripe beautiful avocados.

David: 3:57

I mean like every day there would be like at least two or three, and you would just eat them and have a snack.

Ellie: 4:04

I pay seven bucks for those. Well, for three of them, not, not per avocado.

David: 4:09

Well, nowadays they're getting close to that. I also had a beautiful weeping willow in my house when I was a teenager and I moved to the US and I, uh, heard the name in English: weeping willow, and I didn't know what it meant. And so I always just talked about the weeping willow in the house. And then when I finally understood the meaning, I thought it was so sad that this tree was called the crying tree. And I had a very angsty teenage years from like 15 to 17. So I intensely identified with this weeping willow in our, in our front yard, sad and lonely like myself.

Ellie: 4:51

Oh, my.

David: 4:52

So my two trees are avocado and weeping willow.

Ellie: 4:56

It's cause when I picture your adolescence, I picture it, because you grew up in Nevada after you moved from Mexico, I just picture it as like totally desert barren. And so I'm like shocked to hear that you had a weeping willow because they grow near rivers.

David: 5:10

No, it was that. It was desert. We would be very wasteful, like people in the desert spend tons and tons of water to produce.

Ellie: 5:20

Mm.

David: 5:21

And yards that are not indigenous to the environment. I mean, think about Las Vegas, you know, like everything there is not supposed to be there. And I was just outside of Las Vegas, but yeah, that's a good point. It a very anti- environmentalist front yard.

Ellie: 5:36

But it's interesting that you identified with the tree while you felt lonely and sad because the weeping willow is itself a loner tree. It's a pioneer species. So willow's will grow in kind of outlying areas. They're often loners themselves.

David: 5:52

And given the statistics that we just presented our listeners with about the pretty grim prospect for our trees in the future, maybe the weeping willow is also a stand-in for all trees that can now only grow in very limited areas due to deforestation and environmental change. So there's something really tragic about the figure of the tree in our world, given their increasing persecution by environmental ravaging, and just our shittiness towards nature in general.

Ellie: 6:26

So before you go out and hug a tree, stay tuned with us for the rest of the episode.

David: 6:36

Today, we are talking about trees.

Ellie: 6:39

Why do we overlook these incredible beings in our everyday lives and ways of thinking?

David: 6:44

Are trees intelligent, conscious creatures? And if so, should they have rights?

Ellie: 6:51

And are trees caught in an endless struggle for individual survival?

David: 6:55

Or do they instead exhibit mutual aid and collaboration?

Ellie: 7:01

It's hard to avoid the impression that trees have been excluded from the way we think about everyday life. I recently read the book, The Overstory, which is all about trees. And for the first time started thinking about trees and really noticing them around me. And this just felt awful, initially. I was like, how was I so ignorant of trees and how long have they been around me without me really noticing?

David: 7:26

For a long time, it turns out.

Ellie: 7:28

Even though I was hugging, I was hugging them once in a blue moon and otherwise just completely overlooking them in my daily life.

David: 7:34

Well, it is not just in our everyday life that trees have been excluded. They have also been excluded from the history of philosophy. For example, in the dialogue, the Phaedrus, Socrates very famously makes the claim that the country and the trees teach him nothing, whereas the men of the city do teach him. And this is a pivotal moment, I think, in philosophy's relationship to nature and to trees because Socrates is expressing a view that then trickles down through history that trees don't have much value. They don't have anything to teach us. And we might wonder whether this is simply because trees literally don't speak. So if they don't have language, they have nothing to teach somebody like Socrates.

Ellie: 8:23

Yeah, Socrates. But he, he was a lover. He had a language fetish for sure. Spoken language only; written language, no. But I wonder whether we should really think about teaching only in terms of language? Can't we also be taught in non-linguistic ways. And the philosopher Martin Buber has this really beautiful passage about trees in his book I and Thou, where he talks about the ways that we can fundamentally relate to trees, even though he agrees with Socrates that they don't have language. So just because they don't have language doesn't mean that we can't relate to them. It just means that we relate to them differently. And he talks about how we can either take the tree as an object in the world, or we can take it as a being that addresses us. I want to read a little passage from Buber here. So stick with me. It's pretty, I promise.

David: 9:13

A wonderful writer.

Ellie: 9:14

He's such a good writer. He says, I contemplate a tree. I can accept it as a picture, a rigid pillar in a flood of light or splashes of green traversed by the gentleness of the blue silver ground. I can feel it as movement, the flowing veins around the sturdy striving core, the sucking of the roots, the breathing of the leaves, the infinite commerce with earth and air and the growing itself in its darkness. Seems pretty positive about trees, but that is even still that description I just gave, which is so beautiful is still on the level of us approaching trees as objects for Buber. We can have a shift of mind though, where, he says, if will and grace are joined, not a reference to the TV show, sort of like a matter of I'm trying to relate to the tree differently, but then also there's just a matter of grace or that when I contemplate the tree, I'm actually drawn into a relation and the tree is no longer an it. He says the power of exclusiveness has seized me. And so suddenly the tree isn't even a combination of leaves and the sucking roots, et cetera anymore. It's not an organism. It is a being that confronts me rather than me confronting it.

David: 10:34

And so the tree becomes a thou and can enter into an I thou relationship even with trees, but you know what I, what I like even about his description of the tree as a biological organism or as a physical entity in the world, when he talks about feeling its movement and recognizing its breathing, is that he focuses on the living functions of the tree, on the tree as the kind of entity through which something like a life force is moving. And that is fundamentally different let's say then the rock that is to the right or to the left of the tree, right? So there is something about the tree that allows me to enter into that kind of relationship with it, precisely because the tree is not inanimate. It is an animate being filled with life. So maybe I, as a living being, recognize something in the tree that is similar to me, and that is the movement of life.

Ellie: 11:32

Yeah. And that idea that the tree is a being unto itself, I think you find in ancient philosophy with Aristotle who says that plants do have souls, but Aristotle was actually one of the major philosophers who's responsible for the marginalization of plants, because he says, for instance, that, yeah, like a tree has a soul or a plant has a soul. He talked about plants in general, and it has the power of self nutrition and the ability to grow up and down, but it can't move to different places and it doesn't have passions, sensation, or thinking. So he doesn't actually even think that plants have sensation.

David: 12:08

Yeah, in Aristotle's biology, there is a very clear set of concentric circles, where if we begin with plants, they just have the two basic biological imperatives, which are, they feed themselves and they reproduce so they can maintain their life cycle and then they can pass it on to subsequent generations. That's the first circle. If you pan out a little bit more, you have a larger circle, which is animals, which have reproduction and nutrition just like plants, but then they also have these other things that you mentioned, Ellie. Suddenly they have sensation, they have perception, and then finally, if you pan out even more, you get the largest circle, which is humans who have all the capacities of the plants and all the capacities of the animals, plus the additional ones, which are thought and reason.

Ellie: 12:59

Well, and Aristotle's reason for saying that plants don't even have sensation is that they're made out of earth. So he doesn't think that things that are made out of earth can have sensation, passion, thinking, et cetera, which is sort of weird. Cause it's like, well, plants are made out of earth, what are we made out of? Aren't we also made out of earth.

David: 13:16

Well, no, I think it's because for Aristotle, the distribution of the basic elements, earth, water, fire, and air is different for plants, for animals, and for humans. So it might be that animals are like mostly earth. That's the, that's the element that dominates them. They're yeah. They're like from the earth kingdom, whereas maybe animals have a little bit more of like a principle of action, which might be something like air and fire.

Ellie: 13:44

Does Aristotle buy that view though, the view of the four different elements.

David: 13:47

Oh, yeah, that's his, that's his physics. His physics is that the sub lunary realm, so everything below the moon, is made up of the four elements. So tables and chairs and dogs and cats and Bubers tree are all made according to different combinatorial rules. So there's just a different proportion of those elements. But honestly, I don't know how his theory of the four fundamental elements maps on to his biology and he explains differences between plants, animals, and humans by appealing to different elements playing a larger role in their constitution, that I don't know.

Ellie: 14:28

Yeah, I'm sure I have notes on that somewhere, but we'll, we'll bring it back to trees for now.

David: 14:32

Yes, please. Cause we're getting away.

Ellie: 14:35

Yes. So one of the ancient philosophers who has a view of plants that sometimes people will draw on today is good old Plotinus, who disagrees with Aristotle about the point of trees having some consciousness. So even though Aristotle says, yeah, sure. There's like a plant soul. He says they have no sensation or passion. And on the face of it, Plotinus agrees with that, but he also says that there's some thing resembling plant anger, and he's like, well, how do I explain that, given that I don't think that plants have sensation or passion. And he says that what looks like plant anger is really just an irritation that is a physical ebulition that approaches resentment. Yeah. But it's kind of like an unconscious reaction that plants have it's, it's what we would probably now call instinct, but at least there's like some recognition there. So even as Plotinus is like, no plants don't really have this ability to feel or sense, how much farther do you have to go in order to say that they feel, or at least sense when you're saying that they can experience irritation.

David: 15:49

Yeah, well, but, but if they feel irritation, that's a kind of sensation, right. You cannot not feel irritation. Uh, so maybe it's like a faint level of sensitivity for Plotinus is that, does that strike you?

Ellie: 16:03

No, he says, he says that if plans had sensation, they would also have the recognition of wrong and want to defend themselves against irritation. But because they don't, they don't have sensation or because they don't have sensation, they don't. It's ends up being sort of circular, because you have to just posit that plants don't have sensation.

David: 16:22

Yeah. And closer to the present day, the German phenomenologist Hans Jonas, who was a student of Heidegger, makes a similar claim as Aristotle about the division between plants, animals, and humans. But he says that the difference between plants and animals is that plants don't have a motor system. They don't have way to move around, which is a point that Aristotle also makes. But he says that since perception is necessarily embodied, the way in which we perceive the world and understand our environment is by means of moving through it, plants also have no perception either. They don't have perceptual objects. They're not aware of things that are beyond their immediate boundary-

Ellie: 17:11

Hm.

David: 17:12

with the external world. And on top of that, Jonas says they don't have emotion. And for him, that's really the key, uh, that even if plants have something like a metabolic process that allows them to take in nutrients from the outside, they don't actually have the ability to desire and to have a sense of what is good and what is bad. And therefore they have no subjective experience. So Jonas, who is a phenomenologist, believes that there is such a thing as animal experience, but no plant experience.

Ellie: 17:43

Well and I wonder to what extent that might have to do with the fact that plants don't visibly react in a way that we recognize to harm, right? If you punch a tree, it's going to remain immovable, your hand will hurt, that's a different story from, from tree hugging to tree punching. But whereas like if you punch an animal or a human, there will be a response.

David: 18:05

Oh, definitely. And I think it's the fact that plants appear fundamentally passive and don't give signs that registered to us as pathic, as having a base in suffering, that has allowed a lot of people from Aristotle to Plotinus and even to, uh, Jonas to conclude that there really is an abyss in nature that separates plants from the rest of the animal world, which would be animals and humans. Although of course humans are animals, but in this case, typically those get divided. And at one point in his book, The Phenomenon of Life, which is where he talks about the difference between these biological categorizations Jonas makes the claim that because plants don't move and don't perceive, and they don't feel desire, that means that they never go on adventures. They never have to seek out that things that they need in order to survive, right. So this is classical distinction between the plant and the animal kingdom, which is that plants will just get the nutrients from the air and from the soil without having to go out there to find it, but animals, because they feed on organic as opposed to inorganic material, they do have to forage. They have to go out into the unknown. So there is no seeking behavior.

Ellie: 19:27

Okay. Trees. Don't go on quests.

David: 19:30

Yeah. Although to be fair in his book, The Hidden Life of Trees, which was a major bestseller, the forester, Peter Wohlleben points out that plants actually do need water. So they, there is a kind of seeking behavior that animates them and that moves them. So maybe the distinction between plant and animal in terms of going out on adventures to seek what you need breaks down a little bit.

Ellie: 19:58

Yeah. It was really interesting to read this book in preparation for this episode, because I learned a lot of factoids about trees. And one of the factoids, which I had also come across lately because, you know, people are like obsessed with mushrooms and fungal networks nowadays. But it's the following, which is that trees communicate through fungal networks and they have to devote a lot of energy to sustain the fungi with whom they have a symbiotic relationship. So fungi provide for trees what has been referred to as a wood wide web, where they can send out signals to nearby trees and pick up on potential threats in the environment and communicate that back to the trees. So Wohlleben talks about the fungal networks almost as a fiber optic internet cables. And trees will often have dozens or more species of fungi with whom they're related in this way.

David: 20:53

Yeah. So there might be more of a sense of adventure in the life of trees than we tend to realize, which I guess is the point of that book, whose subtitle is What They Feel, How They Communicate. So maybe this image that we have inherited from ancient and even contemporary thinkers needs to be updated a little bit in light of what we are learning about let's say the fungal network, the wood wide web, the fiber optic dynamics of tree communication. And maybe even about the distinction between plants and animals along the lines of movement. Because I recently read an article that made the claim that the reason that we tend to think of plants as static is because we think about the wrong object and the wrong timescale. So with animals, of course, movement is predicated of the individual organism, right? Like this dog moves with its paws and goes and gets food. But when it comes to plants, we might begin to see movement if we make two little tweaks to our perception of them. The first one is that we have to think not just about the tree, but about the forest as a whole, maybe as a superorganism. And secondly, we have to completely bracket out our own human timescale because trees live for a very long time and they live in a fundamentally different temporal scale. If you look at the evolution of a forest for a long period of time, you actually see the forest itself moving, physically migrating, over time, seeking better and better environmental conditions. So even if individual trees remain rooted to the ground, maybe the forest as a whole, as a supra organism does have that capacity of movement that historically philosophers and scientists have associated with animals.

Ellie: 22:49

Wow. And I think that also just really shows the bias that we as humans have, where if it doesn't appear like the tree is moving to us within a given state, then we're going to say that it doesn't have the capacity for movement at all. But what we're looking at is the wrong object and the wrong time.

David: 23:07

Yeah. And so it's about the limits of our human imagination. The Hidden Life of Trees is a super cool book, but it was really controversial when it came out, Ellie. In fact, there was this letter of opposition that went around when the book first was published that was signed by over 4,000 scholars, most of them experts on trees, actually, who signed the letter in opposition to the book because of what they believe to be the books excessive anthropomorphizing of trees.

Ellie: 23:59

We love a good academic beef.

David: 24:01

Yes, I know. And I, I read some of the criticisms and, you know, there might be something to them. I don't know.

Ellie: 24:08

Yeah, no, there were times when I was reading the book where I wasn't sure what to think. Cause I was like, oh my God, trees have maternal instincts and, and they have language. And then I don't know. It sounds like maybe not, there's a lot that we can glean from the book with all of these incredible examples of the nature of trees. But it did strike me that the language might have been a little overblown at times. So that's good to hear.

David: 24:30

I know. Yes. I have to say, I began actually by reading the criticisms before I read the book. And so I approached the book already with a very high level of skepticism about the claims. Then when I read the book, I didn't really agree with the criticisms all that much. And it's not that he doesn't say those things. He definitely says that trees have language. He definitely says that they have maternal instincts as you point out, which was a particular phrase that a lot of the critics pointed to as, you know, a, one of the more egregious claims in the book.

Ellie: 25:05

Because it wasn't sufficiently backed up by evidence. Same with the language point, right. He wasn't, he was like, trees have language, but he was concluding that based on, you know, studies that didn't necessarily really show that. that

David: 25:15

Even the notion of like mother, right? Like the, the concept of mother doesn't quite apply to trees because sexual reproduction and sexual identity doesn't work in the same way. Anyways, the point being here that then I read the book after reading all these criticisms. And I actually felt like the criticisms, it's not that they were disingenuous, but that they were not entirely fair, because I really read the book as an example of romantic nature writing, as a love letter to trees. So the exaggeration of the language, which at times bordered on the poetic, I didn't mind that at all. I really read that as part of the kind of book that Wohlleben wants write. So at no point did I really feel like you wanted me to think of trees as good mothers who want to nurture their little babies, even though he does have a lot of that language.

Ellie: 26:12

Yeah, I like that because what you point out, David, is in thinking about Wohlleben's book as an example of romantic nature writing, the point is the emotional response and transformation of the way that we think about trees, more than it is about scientific claims about trees. But that said, I mean, the scientists who are writing this letter of opposition, are they disagreeing with the core claim, which is that trees have a hidden interior life, that they are intelligent beings or?

David: 26:46

So yes and no. I think that the term intelligence is very slippery, as is the term interior life, right. What does that mean? Are we just talking about a basic sensation or are we talking about our Cartesian theater with a full on monologue? You know, like.

Ellie: 27:01

Ah, even humans don't have that.

David: 27:04

Yes, good point. So I think we need to dig a little bit more carefully into what it means to say that trees might be intelligent creatures. What does intelligence mean in a non-human and in this case non-animal context? That's the question.

Ellie: 27:23

Well, I was fascinated by the claim that trees communicate with other trees through scent. So for instance, when they get attacked, the saliva of the specific bug attacking them triggers a response that either makes the taste of the leaves suddenly disgusting to the bug or even poisonous and/ or communicates to other trees, Hey, there's a predator out there. put out this toxin, so the bugs don't come to you too. He talked about that in terms of Acacia trees in the savannah.

David: 27:54

Yeah. And so this is a really good example, and there's a lot of interesting stuff in the book about the way in which trees communicate with one another. And, you know, with the fungal network that you mentioned, but his claims about language in particular did make me pause. So for example, in the chapter of the book where he talks about trees communicating with other trees through scent as a way of warning them about all the bugs are here, you better get your defenses up. I decided to look up the reference. By the way, another point of objection to this book is that it actually has very few references for a scholarly-

Ellie: 28:30

Oh.

David: 28:31

This magnitude, which I agree with.

Ellie: 28:33

That's an egregious issue. We hate that.

David: 28:36

Well, I know. It also sounds very elitist and kind of ivory tower-ey.

Ellie: 28:40

I know. I know. I love a reference. I think that's important.

David: 28:42

It has references, but-

Ellie: 28:44

Yeah.

David: 28:45

uh, by scholarly standards. Yes, which is not a lot. Anyways, so where he talks about this warning mechanism, I decided to follow the reference, which is a 2007 article entitled "The Silent Scream of the Lima Bean," where, which for starters is not even a scientific article, it's actually a journalistic report of scientific research presented at a conference by a group of scientists, and the authors talk about tree scent production. And the question here is what are the trees doing when they release these scents that give information about the bug that is currently chomping away at their leaves. And Wohlleben makes it seem as if the trees are sending a message, hoping to influence the behavior of other trees, right. That's what a warning would be. But even the researchers who conducted the experiment in question, especially with lima beans, they actually specify that what the tree is doing when it releases a scent.

Ellie: 29:53

Or the plant in this case, right. Cause-

David: 29:54

Oh, yes, yes, Thank you. Yes. So what the plant, although by extension then trees, because they're, the two get, yeah, there are plant, basically.

Ellie: 30:04

The same way that you and I are animals.

David: 30:05

Yes, exactly.

Ellie: 30:06

chagrin.

David: 30:09

Ellie is really upset about being grouped with animals and with the living by extension. Um, but the, the researchers actually say that what the tree or plant is doing is it's actually trying to communicate with the other leaves of itself. So it's trying to send scent from one leaf to another leaf through the air. And the reason for this is because although there is electrical communication in plants, kind of similar to action potentials in animals, the main difference is that electrical signals inside the plant, literally through the body of the plant, are intensely slow. They are unimaginably slow. So it takes a plant about an hour to send an electrical signal from one leaf to another leaf. And in animals, electrical signals of course are super fast, like milliseconds. That's why, as soon as I touch fire, my brain quickly withdraws the hand. With plants its very slow. And so they solve this problem of slow communication by just literally jumping the information through the air, in the form of scent. But the researchers say, that's really it, the plant is not trying to communicate with anything other than itself, any effect that that scent might have on other plants is entirely accidental. So this is where I was like, oh, the author is going a little bit beyond the research in making it seem as if there is an intentional message to other plants that act as, as a warning system, really.

Ellie: 31:46

Uh, whereas it's really just looking out for number one.

David: 31:48

Number one and only.

Ellie: 31:50

It's interesting too though, because I think this ability to communicate in response to harm, even if it's just with itself, goes against some of the stuff that we talked about earlier about plant's capacity for sensation, because if I punch a tree, it actually might be physically responding. I just don't see it. Okay. It's my punch is probably not hard enough, but let let's say if I harm, if I harm a tree, it is emitting signals are going to enable the tree to protect itself in some way.

David: 32:22

And if we think about intelligence here, one important point that does follow from the research that Wohlleben mentions is that for a long time, people thought that if you do damage to a plant leaf or to a tree leaf, the information about that damage is localized. It never goes anywhere else. But in fact, it seems as if trees do try to integrate-

Ellie: 32:46

Um,

David: 32:47

about what's happening all over the plant. So what happens to the leaf will be communicated to the stem and will be communicated to the roots. So there is that kind of information centralization that already gets us, maybe to something like a kind of intelligence, even if it's nowhere near the intelligence that we might see in an elephant or a giraffe or in a human being.

Ellie: 33:15

So it seems fair to say that even though you have issues with Wohlleben's interpretation of the data as making really broad claims about plant intelligence, you do think trees are intelligent. Do you think they have language or not?

David: 33:30

So I don't feel comfortable yet with the claim about language. So I want to say no to language, yes to communication. There is definitely a lot of signals moving through the fungal network, from tree to tree, but I'm not sure that it's intentional, and yes to intelligence. So I have to give credit where credit is due, because I tend to be somewhat animal centric in my thinking. And this book really made me question my own understanding of plants and to revisit actually some of my philosophical commitments, really.

Ellie: 34:06

What in particular changed your mind on this?

David: 34:09

Well, one thing was his discussion of plant memory. He argues that some plants can remember things that happened to them. And he cites the research of an expert on plant behavior, whose name is Monica Gagliano, who has been publishing a lot of research on what is now known as plant neurobiology. So that- is there cognition in plants? And Gagliano became famous for an experiment that she conducted with plants and water. So there are some plants that if they get hit by a drop of water, the leaves will close up in self-defense, right. They just like close up so that nothing happens to them. The scientific consensus has been that that act of closing up is purely instinctual. There is nothing cognitive, that plants are not thinking. Anytime they get hit by a drop of water, the leaves will close up. And Gagliano found that that's true to an extent. So if you drop some water on the leaves of the plant, it will close up. If you drop another drop of water, it will close up again. But if you do that enough times, at some point, the plant will learn that the drop of water is actually not harmful and it will cease closing up. And so that see, seeing all of the behavior that we thought to be instinctual leads Gagliano and some of her colleagues to postulate that the plant remembered and learned that the water is no longer a threat and to adapt its behavior in light of what has happened in experience. And that's one of the points in the book that made me think maybe plants really do have memory and learning.

Ellie: 36:00

Mm. This confirms my suspicions after rewatching Lord of the Rings recently .That trees can think and talk. Well in Lord of the rings, there are these characters called Ents, which are tree herders. So they're, they're actually different from trees, but one of the main Ents says that there are at least many trees that can think, they're conscious, not all of them, but at least many.

David: 36:26

Yeah, so definitely memory plus learning arguably adds up to some kind of intelligence and consciousness.

Ellie: 36:33

Take that Aristotle.

David: 36:34

As in the scientifically accurate film, uh, Lord of the Rings. Um, but you know, so out of curiosity, I then decided to look up, Gagliano's recent work on plant behavior because that study on memory was already a few years old. And I found a piece that she recently published in Nature, which is about associative learning in plants. So associative learning, a term from psychology, is when you learn to relate to things that are not connected by any natural necessity. So the classic example is the Pavlovian dog, right? That you present food and you ring a bell at the same time, the dog learns to associate the sound of the bell with the scent of the food and so it starts to salivate every time it hears the bell. Now what's really important about associative learning is that that condition stimulus, which in this case is the bell, is absolutely arbitrary. There is no objective connection between the bell and food. And so associative learning is thought to be an indicator of intelligence or consciousness, because it means that the organism is learning something about A on the basis of B when there is no natural connection between A and B. Anyways, so the consensus in psychology is that only animals have associative learning.

Ellie: 38:05

Only we associate the bell with food.

David: 38:07

Only we can make those kinds of association, not just that particular one. Then Gagliano wondered, what would happen if I do a classical conditioning experiment on plants. And so what she did is she exposed plants to light, because of course by instinct, they seek the lights, something that Wohlleben also talks about in his book. And as the plants were growing, she exposed them to air and light in a particular way so that the plants would learn to associate the source of light with wind. And of course in the natural world, there is no natural biological connection between the movement of wind and the direction of the sun. And what she found is that the plants actually do learn to associate those two arbitrary connections, so that at some point they would learn to pursue the wind because they thought that it was a good indicator for light.

Ellie: 39:13

Mm. From Pavlov's dog

David: 39:16

to

Ellie: 39:16

to Pavlov's oak.

David: 39:18

Yeah, to Gagliano's plant. Um, and so the idea here is then that plants are capable of associating arbitrary stimuli and adapting their behavior in light of this. And what is really fascinating here for me as somebody who has a pretty strong interest in theories of consciousness is the claim that the evolutionary theorists Simona Ginsburg and Eva Jablonka make in their recent book,

The Evolution of the Sensitive Soul: 39:44

Learning and the Origins of Consciousness.

Ellie: 39:49

I'm a scientist having so much fun with their titles. I love it.

David: 39:52

Know they're very long. Um, but, uh, Ginsburg and Jablonka, who are evolutionary theorists, they make the claim that consciousness begins with associative learning. Now they don't think that plants have that. They say only some animals, vertebrates, have that.

Ellie: 40:12

And then Galliano comes in and says, here's my study, take that, they have associative learning to therefore they are conscious.

David: 40:20

Yeah, that's, that seems to be a conclusion that would follow, which again, for somebody like me who is largely animal centric, this is honestly kind of mind blowing, the idea that plants are capable of memory, that they are capable of intelligence, that they are capable of associative learning, and that they might be conscious.

Ellie: 40:44

And of course, if trees have consciousness, then this opens us up to questions about ethics. How should we treat trees? And even beyond the ethical realm, there's a really classic essay in environmental philosophy by Christopher Stone called "Should Trees Have Standing?" where he argues that trees should have legal standing. And he says, you might think this sounds wild at first. But there was a time when children, women, and people of color didn't have legal standing and now they do. And hey, if you're not convinced by that argument, then you might be convinced by the argument that corporations already have legal standing.

David: 41:22

Corporations are people.

Ellie: 41:24

If we're, if we're letting Walmart be a legal entity with standing, shouldn't we let the palms.

David: 41:32

Yeah. I, especially if they are conscious, although Stone makes it clear in that article that it doesn't even matter if trees are conscious or not conscious.

Ellie: 41:42

Corporations are not either.

David: 41:43

Yeah. Yes. Although I would say that it definitely helps from a pragmatic standpoint if they are conscious, because legal battles, in my experience, about who has rights and about who has, or doesn't have legal standing, usually devolve into debates about capacities. And that can include cognitive capacities.

Ellie: 42:14

Enjoying this episode? Please rate and review us on Apple podcasts, Spotify, or wherever you listen to your podcasts. You can also connect with us and other listeners on Facebook and Instagram. All right. We're ready for a different academic beef about trees. And it's a very juicy one. there's a contemporary philosopher named Michael Marder who specializes in environmental philosophy and especially plants. So he's one of the guys who writes about how plants are really this invisible and unthought area of philosophy that we need to draw more attention to, but he has some beef with the famous French philosophers Gilles Deleuze and Felix Guattari who in their book, A Thousand Plateaus, which is just like a classic that every person who's interested in theory has not necessarily read, but like knows they should have read. But they give trees a bad reputation.

David: 43:17

Well, I have turned the pages of A Thousand Plateaus, and I'm not sure that I can say that I've read it. Um, but Deleuze and Guattari are probably the most famous contemporary philosophers to talk about trees explicitly from a philosophical standpoint. And they oppose trees to rhizomes and they argue that trees represent, by their very organization, a hierarchical way of thinking. They are a rigid structure, with a core and a margin, as opposed to rhizomes, which have a much more egalitarian structure in which there is no difference between what is at the center and what is on the outskirts.

Ellie: 44:03

Yeah. So an example would be the tuber of ginger plants. Ginger is a rhizomatic rather than an arboreal.

David: 44:11

That's the term.

Ellie: 44:12

Structure. Yeah. So, so a tree structure is arboreal. It has roots a trunk and branches, whereas rhizomes are horizontally distributed plants that don't have say a given center, and above ground, they might appear to be different individuals, but underground, they're actually all clones of the same plant. So Deleuze and Guattari think that the rhizome is really interesting because it gives us a way of thinking about a horizontal, an imminent distribution, of life, rather than an organismic way of representing life, where there is a hierarchical distribution of parts.

David: 44:51

So the key word in what you said, Ellie, for me is decentralization and distribution, right? So rhizomes are decentralized structures that are distributed. They are networks, they are webs. There is no core point that dominates, as opposed to trees, which for them, grow up and down and they are characterized by the root system. So trees, and this is the point that I want to make, are metaphors for structure, for centralization, for bureaucracy, for origin. Uh, so think about, for example, genealogical trees that trace your family ancestry or think in evolutionary terms of the tree of life, right? The notion that there is a central origin from which all species then grow as branches, but there's still clearly a center in a core. So it's that distinction between a centralized structure and a de-centralized almost anarchic movement. That is what is appealing for Deleuze and Guattari about this contrast between the tree and the rhizome.

Ellie: 46:01

And one thing that falls out of that is their claim that any point of a rhizome can be connected to any other. So you don't have to have a logical set of connections between one part of the rhizome and another part of it. And they use their very book, A Thousand Plateaus as a way of testing out a rhizomatic organization. So they say that you should read the first part of the book first, ideally, but then the rest of the book, you can read in any order, I'm too arboreal a thinker. I've been reading it from front to back, but that is, that is kind of one idea behind this, right. They also said that rats are rhizomes, which I just kind of don't get because rats are animals. They're organisms, they're-

David: 46:49

But-

Ellie: 46:49

be arboreal, but.

David: 46:51

You have to think about their, lifestyle. They move through the, what are they called? Like the pipes in the city, uh, right. Like.

Ellie: 46:58

Not to think about the lifestyle of rods to be honest.

David: 47:01

No poor rats. They get such a bad reputation, but I mean, I think if you think about the city, the rhizome underneath, this kind of flow of movement, that is kind of anarchic, kind of decentralized. That is the life of rats.

Ellie: 47:14

Mm. Okay. And one of the things that this really inspired was the Occupy movement. So the Occupy movements and archaic and decentralized distribution of power was in part inspired by the work of Deleuze and Guattari. I do think it's easy to read them as saying trees bad, rhizomes good. But that is an oversimplification because for them, that view is already an arboreal way of thinking. It's the tree like way of thinking to say that one thing is preferable to another, right? That's a form of hierarchy. So they note that trees and rhizomes are actually interwoven. Trees are rhizomatic and rhizomes are arboreal at least to some degree, but I don't know.

David: 48:00

Yeah, I don't know either because Deleuze and Guattari, I mean, they can say that they don't prefer rhizomes to trees as a way of avoiding their own kind of arboreal thinking in their metaphysics, but they give a really strong vibe that, that they do. Plus they've gotten taken up that way by many people who have been influenced by them, namely as making the claim that there are more possibilities for what we might call liberation in rhizomatic relationships, rather than arboreal boreal ones.

Ellie: 48:34

Well, for the Occupy movement to explicitly adopt a rhizomatic power structure, or if we can even still say power structure there, that implies a preference of the rhizomatic to the arboreal, right? The arboreal would be the Wall Street one percenter approach to life. So it's telling perhaps that both of us specialize in 20th century French philosophy, but have barely ever talked about Deleuze and Guattari on the podcast before.

David: 49:04

Yes. Yes.

Ellie: 49:05

Because to be perfectly honest, I have never been that struck by their thinking. I'll leave that prejudice aside for now because we're talking about their view of trees specifically, but I'm taken by Michael Marder's claim that Deleuze and Guattari are wrong about trees. So martyr writes that trees are not actually hierarchical at all. And so Deleuze and Guattari's account of the arboreal is misguided. He says, for instance, sure, trees grow upward and downward, but they also grow outward and they don't even grow from the bottom up. Plus they're deeply dependent on the fungal networks that we talked about earlier and other environmental factors, and they really don't exist in isolation. So I think murder's critique of Deleuze and Guattari on trees might be similar to what you were talking about a while ago, David, which is this misconception that trees are just sort of like solitary things standing still in the forest, whereas maybe we need to take a broader approach and think about the forest as a super organism. That would be rhizomatic.

David: 50:12

Yeah. And thinking of trees, uh, as already rhizomatic rather than arboreal, means that we have to think about trees differently than we have thought about them, both scientifically and philosophically, because this image of trees really differs not just from the one that we get from Deleuze and Guattari in the 20th century, but even from the view of trees that we get from someone like Nietzsche in the 19th century. In many of his writings, Nietzsche uses trees as illustrations of what he calls the will to power, which for him is the basic biological drive that inheres in all living beings to assert oneself and to dominate one's environment. And because the basic state of trees, Nietzsche says, is mutual competition, where the trees are constantly competing for sunlight with other trees and if they don't win, they die, it means they constantly have to struggle or else perish. So this image of trees as like the ultimate expressions of the will to power, I think is closer to Deleuze and Guattari.

Ellie: 51:25

Yeah.

David: 51:25

In, in its assumptions.

Ellie: 51:27

Yeah. And very different from Wohlleben, for instance. For Nietzsche, a tree eat tree world out there.

David: 51:35

Yes, I, yeah, I we're going for puns, I guess. Uh, trees don't really root for one another out there in nature.

Ellie: 51:46

Well, Nietzsche, of course, is working under the influence of Darwinian evolutionary theory in the 19th century with this idea of nature as survival of the fittest. And there is definitely reason to believe that trees do compete with one another. So Wohlleben says, for instance, that trees are the same species will often try and help each other, but they'll compete with other species. But even trees within the same species, if there are a bunch of seedlings, only some are going to survive. Only the strongest will survive.

David: 52:16

You know, this image of nature as red in tooth and claw and the survival of the fittest and utter competition for survival is so common that we tend to think of it as simply objective. It's just the picture of nature that science reveals. But I think we should contrast this view of nature that we get from Darwin and from Nietzsche with a competing view of nature that comes out of Russian anarchist, Marxist scientist in the early 20th century, such as- Yes. So chic, uh, such as, Peter Kropotkin, who writes a lot about mutual aid in the natural world. And he says, look, yes, sometimes animals will ravage one another. It's, it's a rough, brutal world out there. Like Hobbes said..

Ellie: 53:09

Yeah, consent, not really a thing in the natural, animal world.

David: 53:12

Uh, no definite maybe consent isn't, but Kropotkin says, if you really look at the way in which animals live their life in nature, these Darwinian scenes of predator versus prey, of devouring each other, and competing are actually quite rare in the life of an organism. Most of the time, organisms get along with their neighbors pretty well. And there is a lot of evidence to suggest that mutual aid i.e. altruism is something that grows organically in nature, not just with humans, but also with non-human animals. So it's a very different image about what the law of nature is when you let nature run its course.

Ellie: 53:59

More similar to Wohlleben's collaborative vision of trees. You know, in fact, Deleuze and Guattari explicitly associate arboreal thinking with Darwinism, and they talk about the need to move away from a tree of life model of evolution, to a different way of conceiving of evolution.

David: 54:21

Yeah, and so one question we might ask is whether contemporary discussions, for example, about the evolution of altruism and the existence of mutual aid in nature, the fact that animals do collaborate, not just with members of the same species, but even with members of entirely different species, often forming really cool symbiotic relationships, whether that gives us a rhizomatic image of nature that can be contrast with Darwin's arboreal view of nature, as red in tooth and claw.

Ellie: 54:56

I'm also kind of down to just keeping arboreal way of thinking. I don't think, I don't think it's that bad.

David: 55:01

You're like, I only want survival of the fittest, none of this altruistic bullshit.

Ellie: 55:08

Yeah. I'm not ready to let go of arboreal thinking. I don't think it's necessarily as horrible as hierarchy makes it sound, but more than that, I'm with Marder and thinking that like trees are persecuted these days, we need to do what we can to protect them. That's- let's not make it seem like they're the enemy. So with that, I will stick with my trees over my rhizomes and be completely fine that that's a hierarchical way of thinking and go out and hug a tree.

David: 55:41

We hope you enjoyed today's episode. Please rate and review us on Apple podcasts, Spotify, or wherever you listen to your podcasts. Okay.

Ellie: 55:49

You can find us at overthinkpodcast.com where you can email us with questions, feedback, or even requests for life advice.

David: 55:55

You can also find us on Instagram and Twitter at @overthink_pod. We want to thank our audio editor, Aaron Morgan, as well as our production assistant Sam Hernandez. Samuel PK Smith for the original music, and Trevor Ames for our logo.

And to our listeners: 56:09

thanks so much for overthinking with us!