"Is it ok that I prune my bushes?"
These questions, and many like them, pop up whenever I've given a talk or been interviewd about the WHAT A PLANT KNOWS. Truth is, I didn't fully anticipate this take on plant senses, but it seems that the book has, so to say, struck a nerve, with many readers who are concerned for the welfare of their plants.
But indeed, the question of plant sentience is perhaps only an extension of our interest in understanding consciousness in general, and by extension, suffering.
Neuroscientist Daniel Bor recently wrote a great piece in Slate entitled When Do We Become Truly Conscious? that can help us come to terms not only with animal suffering, but plant (lack of) suffering as well.
In analyzing when a a human becomes conscious, Bor writes:
"The evidence is clear that a fetus can respond to sights, sounds, and smells, and it can even react to these by producing facial expressions. The evidence is equally clear, however, that these responses are generated by the most primitive parts of the brain, which are unconnected to consciousness, and therefore these actions don’t in any way imply that the fetus is aware."If we replace "fetus" with "plant" and make a few edits for scientific clarity, we get:
The evidence is clear that a plant can respond to sights, sounds, and smells, and it can even react to these by changing development [many example of this in WHAT A PLANT KNOWS!]. The evidence is equally clear, however, that these responses are generated in the abscence if a brain, and thus is unconnected to consciousness, and therefore these actions don’t in any way imply that the plant is aware.
Obviously in philosophical debates such as these, semantics play a key role. Bor and I don't use the word aware in the same way.In WHAT A PLANT KNOWS I posit the thesis that plants are indeed aware of their environment. But they are not conscious, at least not in the way that Bor uses awareness and consciousness:
"In adult humans, for normal consciousness to occur, it is now generally agreed that two sets of regions need to be intact, functional, and able to communicate effectively with one another: the thalamus, a kind of relay station in the middle of the brain that connects many regions with many others; and the prefrontal parietal network, our most high-level, general purpose section of cortex. If either the thalamus or prefrontal parietal network is substantially damaged, the patient is likely to enter into a vegetative state, with virtually no sign of consciousness."Psychologists, physicians and neurobiologists alike have come to a consensus that suffering, which is subjective, is located in the prefrontal cortex, while pain centers are located deep within the human brain that radiate out from the brainstem. The International Association for the Study of Pain meshes pain and suffering and defines pain as “an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.” So if suffering from pain necessitates highly complex neural structures and connections of the frontal cortex, it follows that plants obviously don’t suffer – they have no brain.
So munch away on your celery stalks; take pride in your ability to chop tomatoes; and prune your oak so that it doesn't obstruct a path. Your plants may "know" what's happening, but frankly my dear, they don't give a damn.