Should communication between pea plants raise tough issues for vegetarians?

I was just about ready to get back into my review of In Defense of Food this week. That is, until yesterday morning, when Michael Pollan tweeted,

Cool piece on how pea plants communicate with one another, possibly raising some tough issues for vegetarians.

The basic science in the blog post, I have to say, is genuinely interesting. The idea is this:

[A] team of scientists from the Blaustein Institute for Desert Research at Ben-Gurion University in Israel published the results of its peer-reviewed research, revealing that a pea plant subjected to drought conditions communicated its stress to other such plants, with which it shared its soil. In other words, through the roots, it relayed to its neighbors the biochemical message about the onset of drought, prompting them to react as though they, too, were in a similar predicament.

Curiously, having received the signal, plants not directly affected by this particular environmental stress factor were better able to withstand adverse conditions when they actually occurred. This means that the recipients of biochemical communication could draw on their “memories” — information stored at the cellular level — to activate appropriate defenses and adaptive responses when the need arose.

Stuff like this is fascinating to me, and I’d love to know more about it. However, I probably won’t look to the New York Times to further enrich myself because the Times seems to have a rule that requires all discussions of plant responses to external stimuli to include a discussion of the ethics of eating plants and its implications for vegetarians (see also this article from December 2009 and this one from March 2011).

I often hear vegetarians dismiss this argument as a disingenuous display of concern for plants, but I think there’s a bit more to it than that, at least when the argument is made well. Some animal rightists argue that killing animals is incompatible with generally accepted ethical principles. The “right” way to make the “plants like to live” argument is to argue that the very same line of reasoning amounts to an argument against eating plants. If the argument could be made soundly, it would present a problem for the argument against eating animals–unless the person making it were also willing to give up eating plants. The point is that an argument based on a need to be logically consistent doesn’t deserve to be taken seriously if it isn’t itself logically consistent. This an instance of the reductio ad absurdum, which I’ve written about in another context. Such an argument, it should be noted, has nothing to do with whether the person making the argument cares about plants or animals, and everything to do with proving that an argument fails to meet its own standards of consistency.

That said, I believe there are good reasons to give a pig more consideration than a pea plant. More than anything, I see this as an argument that arises from imprecision.

The New York Times piece asks,

Is it morally permissible to submit to total instrumentalization living beings that, though they do not have a central nervous system, are capable of basic learning and communication? Should their swift response to stress leave us coldly indifferent, while animal suffering provokes intense feelings of pity and compassion?

I find myself unmoved by this argument because my “intense feelings of pity and compassion” for animals do not arise from the simple fact of the animals’ capacity for “basic learning and communication” nor from their “swift response to stress.” Such an argument would be even more foolish than the New York Times‘s Michael Marder implies. Indeed one could easily envision computers or robots that had similar traits, but most people’s reasons for not eating these entities are entirely selfish. They probably don’t taste very good, they contain toxic substances, they’re hard to chew, they’re likely to scratch our throats and mouths, and they tend to be a lot more expensive than most foods. I doubt any vegetarian would argue that a computer deserves better than to be eaten.

More broadly, I would reject the idea that the existence of plant survival mechanisms is evidence that plants take an interest in living. Indeed, if one considers the process of natural selection, it shouldn’t be surprising that an organism that’s alive today has mechanisms that have increased its chance of survival. According to the theory of natural selection, those organisms with survival mechanisms should be more likely to have survived. That’s exactly how natural selection works.

The question, then, is what makes animals different? I would argue that the difference lies in the fact that animals tend to respond to stimuli in ways that we can relate to. When we watch a video of a pig writhing at slaughter, it’s easy to believe that we’d react similarly if we were exposed to similar stimuli. Because we associate both the stimulus and the reaction with pain, it’s not unreasonable to guess that the pig is experiencing something similar to what what we know as pain. But that’s not quite enough to draw that conclusion; one could envision a robot programmed to react similarly. The most important piece of information is that science tells us that the pig–unlike a robot–has the capacity to experience pain and suffering similarly to humans. The pig’s suffering is similar in all of those ways to an experience that we want to avoid, but it’s much harder to relate to the pea plant in dry soil. In that respect, I think it’s perfectly reasonable to give the pig more consideration than the pea.

I want to emphasize here that I’m not arguing that an organism should be considered based simply on its overall similarity to humans. Instead, I argue for consideration based on sentience and the interests that arise from it but that sentience can only be meaningfully understood by comparing certain traits (for example, nervous systems and responses to stimuli) to their human counterparts. This means that some traits (e.g. intelligence) are not directly relevant. (If anybody wants to propose an alternative, I’m interested to hear about it in the comments.)

Might this line of reasoning lead to a stronger argument for sparing a pig than, say, a chicken? Perhaps, but the issue is complicated by the fact that it takes many chickens to provide the same amount of meat as a single pig. In any case, I think there’s a good case for giving either more consideration than a pea plant. I’d feel less comfortable saying the same of an ant or an oyster, and that doesn’t particularly bother me.

Inevitably, some will say that this line of reasoning is anthropocentric. Perhaps so, but I don’t see that as much of a criticism at all. Specifically, insofar as it gives precedence to sensations similar to those that we know as humans, I don’t think it’s any more anthropocentric than making decisions based on what we know (and can know) as people. And I much prefer that to the alternative.



  1. Dave Rolsky said

    I generally agree with your argument, but I’d caution against using that robot example. At what point does a robot “programmed” to mimic pain actually start to feel pain? How are we animals not also also robots “programmed” to react to pain?

    I think it’s obvious that with today’s technology, we are not capable of creating a sentient artificial life form, but that day may come. I’m fairly sure this will happen eventually, though I doubt it will happen in our life times. I hope that when it does we humans recognize that these life forms have same rights as all other sentients.

    The great civil rights issue of the 22nd century may well be rights for artificial sentients.

    • Adam Merberg said

      Hmm. I’m not sure if you really generally agree with my argument if you’re concerned about sentient robots. Given that my argument depends on homologous structures, not just similar reactions, it’s hard to see how that would allow for sentient life to be made from electrical circuits, but we’ll see what the future brings.

  2. I agree with you that the real issue is whether a being experiences pain/suffering, not whether it “reacts” or “communicates”.

    Part of the problem here arises from an equivocation between various meanings. To say that a plant “communicates” with another plant can simply mean that it sends signals to the other plant that bring about a change in the other plant. But it can also mean that the first plant is a conscious being that is sharing its thoughts with the other plant. These are two different meanings, and we shouldn’t confuse them. The latter has clear ethical implications; the former, not so much.

    When you say, “[S]cience tells us that the pig–unlike a robot–has the capacity to experience pain and suffering similarly to humans”, I’m not sure what you’re talking about. Could you elaborate a bit?

    When you say that an organism’s intelligence isn’t “directly relevant”, I assume you mean that it isn’t directly relevant to what counts as morally problematic harm to the organism. In other words, if I’m deciding whether it’s okay to smash X with a stick, X’s intelligence per se is not a relevant consideration; all that matters is how much smashing X will decrease X’s pleasure and increase X’s pain (or something like that).

    Depending on my mood, I might tend to agree with you about that, but I think there’s a powerful objection to your claim. If we treat pleasure and pain as the only morally relevant considerations, then it can seem as if we don’t care about organisms themselves at all: organisms become mere containers for the pleasure that we’re trying to maximize and the pain that we’re trying to minimize. There’s clearly something wrong with that picture. If we care about an organism’s pain, it’s out of respect for the organism. Now, if one thinks that being intelligent is in some sense “better” or “nobler” than the alternative (“It is better to be a human being dissatisfied than a pig satisfied”, as J.S. Mill put it), then one might think that more intelligent beings (e.g. humans) deserve more respect than less intelligent beings. This objection certainly has some counterintuitive implications—for example, it implies that harming children and the mentally handicapped is more morally acceptable than harming adults and Mensa members—but it’s something to think about.

    • Matt said

      Joseph, one has to be an individual organism to experience suffering or pleasure. The suffering or pleasure doesn’t exist separate from the organism; thus, saying suffering is the morally relevant issue is really saying the organism’s experience of suffering is the morally relevant issue.
      Congrats to you, Adam, for treating Pollan with far, far more respect than he deserves. Anyone who doesn’t see (or claims not to see) an inherent and not-necessary-to-analyze difference between biting a carrot and torturing a pig has long ago crossed the line where they deserve any consideration. Pollan is a hack far, far worse than Nina Plank.

      • Matt, I agree with you that suffering or pleasure doesn’t exist separate from an organism. My focus was on the intelligence issue. I was trying to come up with a possible argument for favoring more intelligent beings over less intelligent beings. (Pretend, for the moment, that we actually have an uncontroversial definition of, and way of measuring, “intelligence”.)

        My idea was simply this. If it’s morally wrong to cause suffering, that’s presumably because organisms are worthy of some sort of respect. Now, maybe more intelligent organisms deserve more respect than less intelligent ones. If so, then causing a certain amount of suffering in a pig might not be as bad as causing the same amount of suffering in a human being. (Of course, it would not in any way follow that hurting—or eating—a pig is okay. That’s a separate argument.)

        In case it wasn’t clear, I’m not entirely comfortable with this line of reasoning. As I pointed out, it seems to imply that hurting young children isn’t as bad as hurting intelligent adults (since the children aren’t as intelligent). I just thought that it was something worth thinking about.

    • Adam Merberg said

      When I say that pigs and humans experience pain and suffering similarly to humans, I’m referring to the similarities between the human and pig nervous systems. I could get a few references on this if you like, but that’s the basic idea.

      When I said that intelligence isn’t “directly relevant,” what I meant was that it’s not relevant, except insofar as as it may be correlated with the other things that are important.

      Finally, I don’t think this line of argument precludes caring about individuals at all. I’m not saying (as a utilitarian would) that all we should care about is the total amount of pleasure and suffering, but that when we make considerations of an organism’s interests, these are the things we should care about.

  3. […] If only Michael Pollan could think things through with half the care that Adam Merberg does. Link. […]

  4. David Basham said

    “If we treat pleasure and pain as the only morally relevant considerations, then it can seem as if we don’t care about organisms themselves at all.”

    Agreed. What if a human/animal is killed painlessly or genetically altered so that s/he doesn’t feel pain. In my opinion, killing a being that can’t feel pain is still unethical.

    Tom Regan’s argument is something like this:

    All humans are said to possess inherent value, meaning that we have value as individuals independent of our usefulness to others. In addition, it means that we have the right to be treated with respect, and therefore the right not to be harmed. According to Regan, inflicting death is the ultimate harm, even if it’s painless, because it deprives the victim of future opportunities and satisfactions. In order to ensure that we do not pave the way for injustices such as slavery or sexual discrimination, Regan insists that those who have inherent value have it equally, regardless of race, gender, religion, or otherwise. The determining factor in deciding who possesses inherent value is not whether one is wealthy or poor, intelligent or mentally ill, or talented or unskilled. The single similarity that we all share, which is the basis for possessing this value, is the fact that we are the experiencing subjects of a life. That is, we are conscious beings that care about what happens to us and we have a life that matters to us despite whether or not it matters to anyone else.

    Plants are living beings, sure. But, they are not subjects of a conscious life.

    • David– I hadn’t thought of the example of painless killing, but I think it nicely illustrates the difference between just caring about pain (a position that almost no one probably holds) and caring about the organism that’s feeling pain.

      I’m not familiar with Tom Regan’s work. What does he think gives a being inherent value? Is it consciousness? (That’s what I suspect, but I notice that you said “All humans…” rather than “All conscious beings…” when summarizing Regan’s views.)

      • David Basham said

        Hi Joseph,

        Regan asks why we consider all humans to have inherent value. Then, he notices that what we all have in common is that we are the subjects of a life. He explains that it would be speciesist of us to claim that humans are the only creatures capable of possessing inherent value. And, he concludes that, like humans, animals are also the subjects of a life and, as such, must also possess inherent value and its associated rights.

    • Adam Merberg said

      Thanks for the comment, David. Because I was trying to argue somewhat generically, without reference to any particular philosophical theory, I used the terms “pleasure” and “suffering” somewhat loosely. So I would also include any sort of sentient “wanting to live” when I say pleasure.

      As I understand Regan’s philosophy, this notion of inherent value is related to being the “subject-of-a-life” and I am curious how he defines that in a way to exclude plants like peas which communicate. I don’t think it can be as simple as animals have inherent value and plants don’t. Biologically, animals are multi-cellular organisms who pass through a stage of embryonic development in which they are a hollow ball of cells, and I have trouble seeing why that characteristic should have moral weight.

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  7. No. 534 said

    This is a nicely written blog post, well thought, fair and nuanced as always.

    However, I don’t think that we really need to spend much time on a plant sentience rebuttal from Michael Pollan’s one hundred or so character count tweet.

    If he genuinely delved into the ethics of animal ethics and what motivate vegetarians he would not make such an idiotic comment.

    I hate to denounce arguments as stupid or idiotic as a way to dismiss them but I’m sorry, if this idea has really only just occurred to Pollan than he’s either no where near as intelligent as people give him credit for or he’s being outright disingenuous. Since he has an interest in botany and much of his narratives involves personification of plants to the point of granting them agency, I can’t believe that this idea could have popped into his head the day of his tweet.

    Either he’s an idiot, or he’s trolling, but neither motive gives us any further reason to take him as a serious scholar. He officially joins the echelon of Lierre Kieth and company in their style of abject foolishness. It’s no longer an authentic discussion. It is on par with the futile activity of debating Creationists. Pollan has now made it clear that he is unwilling to have a genuine exchange of thoughts on animal ethics. He isn’t engaging vegetarians or his general audience in good faith.

    A conversation about plant sentience is fine, that’s not the problem here. It’s the typical jab at vegetarians regarding plant sentience as if vegetarians haven’t ever thought about the issue when one of the top five questions behind “Where do you get you’re protein?” is “What about plants?”

    When this sort of inquiry comes from people who really should know better as to the legitimacy of the argument, it’s inexcusable because they really should have investigated the myriad of vegetarian responses that address the question.

    What does a vegetarian book originally published in 1899 and is available on the Internet for free have to say?
    The Logic of Vegetarianism by Henry Stephens Salt
    Chapter – The Consistency Trick
    I must here quote a passage from the “Science Jottings” of Dr. Andrew Wilson. Note the triumphant tone of the unscientific scientist as he rushes to his absurd conclusion:

    “I have not yet finished with the food faddist. Suppose I find a vegetarian who, more consistent than the run of his fellows, will not touch, taste, nor handle milk, eggs, cheese, or any animal product whatever. I think it is still possible to show him that he is infringing the code he lives by, in so far as its pretensions with the sacredness of life are concerned. Plants, no less than animals, are living things. Their tissues contain living protoplasm, which is the essential physical basis of life everywhere… I am afraid that the consistent vegetarian must no longer kill a cabbage if he is to live up to the standard of morals he sets up as a kind of fetish in his diet regulations; and to lay low the lettuce, or pluck the apple from its bough, is really a direct infringement of the code which maintains that you have no right to kill any living thing for food. Really this is a monstrous doctrine when all is said and done.”

    It is a monstrous doctrine; and what are we to think of a man of science who attributes such absurdities to vegetarians, and thereupon holds them up to public contempt as inconsistent, when by making inquiry he might at once have learnt that the blunder was on his own side? Once more, then, be it stated that it is not the mere “taking of life,” but the taking of life unnecessarily that the vegetarian deprecates, and that no criticism of vegetarianism can be of any relevance if it ignores the fact that all forms of life are not of equal value, but that the higher the sensibility of the animal, and the closer his affinity to ourselves, the stronger his claim on our humaneness.

    It is by no means a complete response, but it certainly addresses the topic adequately. That a recent science article stateing plants communicate doesn’t affect what Salt wrote over a hundred years ago. It’s certainly not news to vegetarians that plants are alive. Ancient Eastern vegetarians have always held this idea to the degree that souls could migrate interchangeably through plants, animals, and humanity. This idea didn’t hinder their vegetarianism, the opposite really, making it more of an imperative. If that seems zany, keep in mind that Darwin essentially reintroduced the Western world to the concept minus the metaphysics. All life is indeed kin.

    I can somewhat excuse the stream of NYTimes science writers playing at ethicists when discussing plants (just like back in Salt’s day), because I have little reason to expect that they have made more than a cursory investigation on the subject. Pollan has no excuse.

    I do scratch my head at the volumes of science articles on how unique and special certain animals are with no mention of how that should inform our ethics. Remember that February 2012 TIME Magazine cover article from a few months ago, The Science of Animal Friendships.

    Yes, friendships. That was the unavoidable word used to describe animals’ social interactions. Not a peep about how this “new” information might affect humankind’s ethical interactions with animal kind.

    I dare Michael Pollan to do a full write up on his impression that better understood complexity of plant life undermines vegetarianism. I double dare him. Sure, less critically minded people with their biases fully buttressed lap up that sort of self-reassuring pabulum, but if you have the time, notice how well calls for plant and bacteria welfare by Fiona Chambers went in this recent Intelligence Squared meat-eating debate.

    Intelligent people, meat-eater’s or not, so long as they are being honest in their inquiry, don’t buy the “plants void vegetarianism” argument and realize how desperate and pathetic it really is.

    Finally, I leave you with an excerpt of a book first published in 1975, that according to the pages of The Omnivores Dilemma, Pollan at least claims to have read.

    Animal Liberation by Peter Singer
    Chapter 6 – Speciesism Today
    In the absence of scientifically credible experimental findings, there is no observable behavior that suggests pain; nothing resembling a central nervous system has been found in plants… Therefore the belief that plants feel pain appears to be quite unjustified.
    So much for the factual basis of this objection. Now let us consider its logic. Assume that, improbable as it seems, researchers do turn up evidence suggesting that plants feel pain. It would still not follow that we may as well eat what we have always eaten. If we must inflict pain or starve, we would then have to choose the lesser evil. Presumably it would still be true that plants suffer less than animals, and therefore it would still be better to eat plants than to eat animals. Indeed this conclusion would follow even if plants were as sensitive as animals, since the inefficiency of meat production means that those who eat meat are responsible for the indirect destruction of at least ten times as many plants as are vegetarians! At this point, I admit, the argument becomes farcical, and I have pursued it this far only to show that those who raise the objection but fail to follow out its implication are really just looking for an excuse to go on eating meat.

    In addition to the numerous corrections and well-reasoned critiques already undertaken by this blog, this is the final straw for Pollan.

    That’s the power of Twitter I suppose, in such a brief comment, Michael Pollan has exposed himself as ridiculous and irrelevant.

    • One minor correction: only some “ancient Eastern vegetarians” believe that souls can transmigrate into plants. Jain vegetarians believe this (they even classify different vegetable foods according to how many souls they contain; I believe that root vegetables are supposed to contain the most), but, to my knowledge, most Buddhist vegetarians do not.

      • No. 534 said

        I had Jains in mind when I wrote it, being the “first” vegetarians as far as history records whose ideas likely trickled down into Hinduism and Buddhism. While writing, I original spelled out their system of sentience levels ranging from living (humans- 5, animals-4-3 depending on senses, and plants-2) to inanimate objects (water and stones -1 since they can “move”). My post was getting long, but I still wanted to include the idea that vegetarian consideration for plants is an ancient topic, so I cut it and edited it down a bit loosely.

        Vegetarian Hindus and Buddhists generally didn’t believe that plant have souls so are excluded in the cycle of reincarnation, but this shows that they thought about plants and provided reasons as to why they would be omitted. They felt plants lacked ability to acquire experience, somewhat similar to why modern Western vegetarians aren’t wringing their hands with qualms over eating plants.

        I assume vegetarian Buddhists and Hindus would be as unfazed by reports of plant communication as most vegetarians. Of course plants are alive and communicate; everyone knows they grow and attract animals and insects with scents and visuals. Root communication with other plants is hardly shocking especially if anyone has watched David Attenborough’s series on plants.

        But you are correct, not all ancient vegetarians believed the exact same thing, though the reasons for not granting strong moral consideration for plants is compatible even today.

        My point stands, the idea that vegetarians haven’t given thought to plants just doesn’t hold up to anyone who claims to have explored animal ethics and is adequately well read on the subject.

  8. Generally agree, the question isn’t whether the beings can respond to stimuli but rather whether they suffer.

  9. I have to wonder whether Pollan or any other anti-vegan who makes this argument really understands anything about plant evolution. Most of the plants humans eat are angiosperms, many of which have co-evolved with animals to the extent that the plant’s reproduction actually depends on getting its parts eaten — or at least, removed and transported — by animals. And further, it’s possible to eat plant foods without actually killing the whole plant. But we can’t eat just parts of an animal and leave it to re-grow the part we ate; eating an animal is always a life-and-death decision. Eating a plant is not. Plant plasticity and angiosperm dependence on pollinators and animal herbivory are two facts of plant biology that undermine this “plants have feelings, too” argument.

  10. […] “Should communication between pea plants raise tough issues for vegetarians?” by Adam Merberg on his blog Say what, Michael Pollan? […]

  11. M said

    Orders of magnitude more plants must be destroyed to produce animal foods than to produce plant foods. This is because the food-animals themselves must be fed plants in the first place.

    Being vegan therefore helps plants.

    Please don’t let Pollan or any other carnist apologist lead you down the tricky red herring path of trying to argue about plant sentience. It’s irrelevant.

    Veganism helps plants – period.

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