Newsletter - Animal Writes sm
25 July 1999 Issue

The Fallacies Behind the Plant Pain Argument
By Ted Altar

Many are destined to reason wrongly, others, not to reason at all; and others, to persecute those who do reason. -- Voltaire

How, then, could anybody seriously entertain this humbug of plant pain? Remarkable! But I guess it is not so remarkable if we keep in mind the dogged intent to debunk the claims of animal rights, seemingly no matter at what cost to good sense, rationality, or even established scientific fact. Since, as we have seen, many would claim to be avowed ethical subjectivists, at least when it is convenient to do so, I guess we should not be surprised that rationality and intellect is merely made sullied handmaidens for advancing their quest to discredit the case for animal rights.

What follows, dear reader, are five of the common flaws of reason masquerading as arguments on behalf of plant rights.


In the name of open-mindedness, we are asked to take seriously the claim of plant pain because the disbelievers and the incredulous simply cannot prove that plants have not felt pain, or that our knowledge of such things as with many other things, is simply incomplete and uncertain. For instance, it has been said that:

"The simple fact that 'cruelty' cannot be DIS-proved introduces reasonable doubt into this argument."

Here we have the presumption of innocence found in a court of law being inappropriately transferred to how scientific theories are to be established or seriously entertained. Normally, we would argue on BEHALF of a scientific theory by presenting evidence for it, not by pointing to our current lack of evidence unless one is arguing AGAINST a theory. The plant pain promoters would turn the logic of scientific justification on its head.

Now, in a general or ultimate sense it is TRIVIALLY TRUE that there is no final "proof" against such wild notions, but then there is also no ultimate proof against unicorns or ghosts. It is a well known INFORMAL FALLACY to conclude from a lack of disproof for something's existence that it therefore exists or must be taken as a serious possibility for existence. That is to say, it is simply false to argue that a proposition is true simply on the basis that it has not been proved false. The idea here is to try to persuade people of a proposition which avails itself of facts and reasons the falsity or inadequacy of which is not readily discerned.

This flawed logic is technically referred to by logicians as the "ARGUMENTUM AD IGNORANTIUM" (argument from ignorance). This is a logically invalid argument, one that would exploit our common ignorance of things. Now, you might ask, why shouldn't we permit speculative theories to enter into our foundation of ethics. Consider, however, the following example:

"No breath of scandal has ever touched the mayor, therefore she is MUST be incorruptibly honest".

Maybe she is and maybe she is not, but our ignorance does not establish the truth or falsity of the conclusion that she is incorruptibly honesty. It is simply unfair to employ our ignorance as the sole basis of support for some social/public concern.

Similarly, what we DO KNOW about how animals experience pain and suffering is of relevance for a system of public ethics. What we do know about plants is that they DO NOT HAVE a nervous system nor a structure at the cellular level designed to process information in a manner that would conceivably enable a conscious suffering of pain or discomfort. What we do NOT YET KNOW about the workings of plants, of how consciousness in general is enabled, or of how the universe as a whole works, is simply not relevant. It is one thing to plea for open-mindedness, it is quite another to promote intellectual promiscuity under the same banner.


To understand this very slippery and flawed reasoning that logicians refer to as the informal fallacy of EQUIVOCATION, consider the following example:

"The end of a thing is its perfection; death is the end of life; hence, death is the perfection of life."

Note the two senses of the word "end" and how the last part of the sentence confuses them. The word "end" may mean either "goal" or "last event." Both meanings are legitimate, but to confuse the two in an argument is a fallacy. In the example above we have two legitimate premises but a false conclusion that does not follow from the premises, unless we remove the equivocation and rewrite, say, the first premise as:

"The LAST EVENT of a thing is its perfection."

But such a premise is patently false.

This is exactly the kind of flawed argumentation that is occurring with our promoters of plant pain. For instance, the term "sentient" is deemed applicable to plants given ONE of its meanings to simply be the "responsiveness to sensory stimuli." After arguing further that what plants do at a molecular level can be deemed a "sensory response," even thought they do not possess specialized organizations of tissue called sense organs (see error #3 below), they would then have us accept the designation that plants are "sentient."

Let us, for the sake of argument, accept their twisted meaning of the term of "sentient" to simply mean a functional reaction on a biochemical or cellular level to noxious or warning stimuli. In this sense, they will argue that a plant can be said to be "sentient." But at a different juncture they would then have us conclude that because plants are indeed "sentient" they also "feel" tissue injury or assault as "unpleasant"! What the wily plant pain promoters have done is simply bootleg a false conclusion by switching between two quite difference meanings of the word "sentient." Permit me to lay it out:

premise 1:
Plants are responsive to "sense" impressions

premise 2:
As defined in the dictionary, anything responsive to sense impressions are sentient

conclusion 1:
Plants are sentient

Note that premise 1 employs the word "sense" in a very restrictive manner to mean, for the plant pain promoters, "reactions to certain stimuli." Now, for them to jump from this minimal and idiosyncratic usage of "sentient" to the issue of plant pain, our wily abusers of ordinary language IMPLICITLY are forwarding something like the following argument.

conclusion 1:
Plants are sentient

premise 3:
Sentient beings are conscious of sense impressions

conclusion 2:
Plants are conscious of sense impressions

premise 4:
To be conscious of a noxious stimuli is felt as unpleasant

conclusion 3:
Noxious stimuli to plants is unpleasant

From unpleasant we then arrive at plant pain. Of course, our plant promoters will protest that they never said that plants have "consciousness" or "feel" pain, but only that they respond in a manner similar to how we respond to pain. Well, if that be truly the only claim and no more, then there is simply no relevance whatsoever of such an idiosyncratic notion plant "pain" to the real ethical issue of animals suffering from felt pain. If it is not irrelevant, then we have either one of 2 results:

1. Equivocating on usage of "sentient" to bootleg a false conclusion. This is a logical, not a semantic, fallacy.

2. Redefining what ordinary people mean by pain and suffering so that these terms no longer refer to a conscious awareness of pain/suffering.

Now we have the error of irrelevant re-definition. This brings us to the next error of reasoning.


For most people, "sentient" designates the capacity to feel. That is, it would refer to a mental state, not a mere set of behaviors. The Oxford English Dictionary lists 3 core meanings, of which the plant pain promoters will selectively choose only one, it being the most minimal definition, namely:

"def 2: Phys. Of organs or tissues: responsive to sensory stimuli."

Of course, they do not look any further. If they were, they might be surprised to discover that the word "sensory" refers to the organs of "sense" or belonging to "sensation" In turn, the words "sense" and "sensation" refers to the organs or mental states of perception, of psychical affection, of consciousness, etc. Indeed, it is designated right at the beginning that "sensation" is "now commonly the subjective element in the operation of the senses; psychical feeling" (OED). The meanings that predominate refer to mental states, and as we have noted, all mental states are marked by consciousness. Yet, our plant pain promoters ignore these obvious conventions of ordinary word meanings and would legislate their own. And what motivates this re-definition of our terms? Certainly, not to promote clarity or scientific accuracy. If plants have "pain" but no consciousness then what are we to make of such muddy oxymorons as that of an "unconscious pain" or an "unfelt pain"?

If our promoters of plant pain weren't so bluntly serious, this might all be very funny. Indeed, good puns and amusing gaffs result from an incongruous and inapposite word usage. For example, someone once stole the seats from all the toilets in a Canadian RCMP station. The official press release by the Mounties said that they still had nothing to go on. Methinks our pain promoters also have nothing to go on.


Now, we have been entertained by our plant pain promoters of some interesting facts like that of oak trees diverting some of its activity to an increase production of tannic acid in respond to, say, a Gypsy moth invasion. We are informed that: There IS a parallel here, and the relative complexity of the sensory and interpretive mechanisms is irrelevant.

The cruel fact remains, however, that PARALLELS DO NOT MAKE FOR IDENTITIES. Indeed, how something is achieved is just as important as what is being achieved in order to properly attribute there to be identity. For animals, conscious motivation to avoid pain figures very large in how they would avoid or mitigate pain. Pain is not something that is unfelt. It makes no sense to speak of "unfelt, unconscious pain," yet our plant pain promoters will insist upon there being a morally relevant parallel.

To illustrate this point about identity, please permit me to work from a different and more familiar example. Now, it has been argued that computers "think" as evidence by their capacity to manipulate symbols. What shall we make of this? Searle's (1980) well-known Chinese room argument, however, at least makes clear that computers as syntactic engines are not "understanders" of language even if they should one day be successful at translating from Chinese to English back to Chinese. The subjective life and mind accompanying a person's performances would seem to involve more than the computer's superior efficiency at manipulating data according to sequences of algorithm-governed operations. To even here speak of "rule-governed operations" is misleading since it suggests we can talk of these machines under the description of them "following rules." Shanker (1987) makes the case that this violates our logical grammar of rule-following being a normative rather a mechanical action and that it is an action predicated on some necessary minimal "understanding" of the rule. Due to the literal ascription implied by this trope about computers, we are lapsing into the same kind of conceptual confusion that would occur if we were to literally ascribe to the members of a meeting that they were following Robert's rules of order even though they were ignorant of, or did not understand the rules. If we were to say such a thing, it would only be FIGURATIVE for simply saying that the members just happen to be inadvertently or unknowingly abiding by Robert's rules. Notwithstanding the generosities of idealization and wishful rhetoric, the computer analogue still remains a metaphor and one that too often invites a misleading anthropomorphism (Dreyfus, 1987).

Indeed, as the problems of the computer metaphor are becoming more widely appreciated and, as Michie (1982) notes, the former heuristic value of the metaphor is being replaced by more exact and fruitful formalizations and mathematics, the metaphor is beginning to become less frequent in the scientific prose of AI science itself. While anthropomorphic speculation inaugurated both the animal and computer models, it is a circumspect anthropomorphism tempered with naturalism that now appears to be the most fruitful approach for the understanding of animals (Griffin, 1981), but it is an "objectivist," or more precisely an electrical-mechanical and symbolic-mathematical prose, that is more fitting for AI. With respect to plants, the language of mental states is simply addleheaded and daft.


Now, we have been told that "there IS some evidence which shows that plants are "sentient", in the broad sense of the word." Hmm, more likely the narrow and twisted sense of the word. But again, all we have is simply the interesting but morally irrelevant facts about plants reacting to certain noxious stimuli, or to the signaling molecules of other plants under attack. We are then asked about how this might be different from our own sense of smell. They would ask, "is this not equivalent to plant sensation or of a plant sensing its environment?" By now, we should be able to readily reply that such usage simply stretches our ordinary definitions of the word "sense." Mere behavioral reactions and avoidance to certain stimuli is insufficient for the attributions of mental states like that of perceptions and knowing sensation. Again, we have either an equivocation of usage to a bootleg false conclusion, or we simply have a re-definition of our ordinary meanings to something idiosyncratic and morally irrelevant. HOW the plants do what they do is just as important as the function of what those reactions subserve.

Here is an example of over-interpretation that was due to this error of only observing the end result and not the means. It was once thought that army ants were comprised of a strategic military column marching through the forest with direction, purpose and foresight. Well, it turns out that these ants simply follow the smell of the ants in front, and in turn the leading ants simply, in a somewhat random manner, lurch or are, pushed forward. If these ants were to be placed on a flat surface and the leading ants were to make a circle back to the rump end of the column, the marching column of ants would simply go around and around until they died. Where is the intentional purpose, planning and foresight? There is no scouting ahead of the terrain, no deliberative leadership, just a very simply mechanism that under normal conditions in the uneven terrain of the forest works very effectively to keep the ants ever moving forward in search new food supplies. The key point is that for many centuries people over-interpreted what was going on simply because they only observed the overt functional behaviors and not the means and enabling conditions for those behaviors.


Patient reader, permit me to finish with one last observation. Hypochondriacs are, as you know, people who believe in pains that simply don't exist. This much they have in common with our plant pain promoters. Of course, hypochondriacs also are easily persuaded that they must themselves have what even the most superficial description of an illness would describe. I'll leave it to the reader to decide if this parallel also applies to our plant pain promoters. Now, there is the amusing story of one such person who after hearing a lecture on diseases of the kidney, immediately phoned his doctor. The good doctor patiently explained that that particular disease there were no pains or discomfort of any kind, whereupon our hypochondriac gasped, "I knew it, my symptoms exactly!"

* Dreyfus, Hubert L. (1987). Misrepresenting human intelligence. In Rainer Born (Ed.), Artificial intelligence: The case against. London: Croom Helm.
* Griffin, Donald R. (1981). The question of animal awareness: Evolutionary continuity of mental experience (2nd ed.). California: William Kaufmann. Another good book that I would highly recommend.
* Michie, Donald (1982). Machine intelligence and related topics. London: Gordon & Breach Science Publishers.
* Searle, J. (1980). Minds, brains, and programs. Behavioral and Brain Sciences, 3, 417-457.
* Shanker, S. G. (1987). The decline and fall of the mechanist metaphor. In Rainer Born (Ed.), Artificial intelligence: The case against. London: Croom Helm.
* Taylor, Charles (1964). The explanation of behavior. London: Routledge & Kegan Paul.

Go on to The Dog Hause
Return to 25 July 1999 Issue
Return to Newsletters

** Fair Use Notice**
This document may contain copyrighted material, use of which has not been specifically authorized by the copyright owners. I believe that this not-for-profit, educational use on the Web constitutes a fair use of the copyrighted material (as provided for in section 107 of the US Copyright Law). If you wish to use this copyrighted material for purposes of your own that go beyond fair use, you must obtain permission from the copyright owner.

Home Page




Your comments and inquiries are welcome

This site is hosted and maintained by:
The Mary T. and Frank L. Hoffman Family Foundation
Thank you for visiting

Since date.gif (991 bytes)