Let me preface this by saying that I feel that suffering is the actual experience of feeling any sort of cruelty/pain inflicted on a sentinent creature, whether the pain is inflicted intentionally or unintentionally. The pain itself is definitive of the suffering. It is impossible for anyone in a position of objectivity to judge whether or not a being can actually "feel" the pain-this is true in the case of humans believed to be "brain dead" and animals believed to be in a similar circumstance. Since we have no ability other than to speculate on the ability of any one subject to experience pain, I feel that we are in no position to impose any action that would, under all normal circumstances, result in a painful experience, whether or not we
believe that the action will inflict pain or not. It is up to humans to exert proper judgement and compassion toward members of our own species and members of other species because we have the capacity to understand the root of pain and the consequences of actions, where as animals are, for the most part, under our mercy. Having said that, I found this quote today on the PETA website:
“What about plants?”
There is currently no reason to believe that plants experience pain because they are devoid of central nervous systems, nerve endings, and brains. It is theorized that animals are able to feel pain so that they can use it for self-protection purposes. For example, if you touch something hot and feel pain, you will learn from the pain that you should not touch that item in the future. Since plants cannot move from place to place and do not need to learn to avoid certain things, this sensation would be superfluous. From a physiological standpoint, plants are completely different from mammals. Unlike animals’ body parts, many perennial plants, fruits, and vegetables can be harvested over and over again without dying.
So, from this standpoint-one I believe Sparky may be willing to consider (meant earnestly, not offensively)-pain is a reflex, a natural defence mechanism. The presence of a brain and central nervous system results in the reaction of pain to any abnormality as a warning to the being to stop, to revaluate, to flee, to defend. Therefore, if humans exploit this natural reaction (one that we invariably sympathize with as we experience it as well), then we are in essence being cruel to the animal by knowingly causing it to suffer. Following this reasoning, it would seem to me that the actual definition of suffering is therefore the unnecessary prolongment of this natural defense and reaction by outside forces beyond the subject's cotrol. So yes, I feel that the ability to feel pain followed by the experience of prolonged pain is the root of suffering; one suffers when the pain they experience cannot be controlled or stopped, as their nervous system's central defense mechanism is being exploited and controlled.
Now of course, I believe there to be an ethical issue attached to this as well, meaning that any being that we are aware has the
potential to experience pain should not be treated with cruelty despite a belief that they are no longer physically able to feel the pain due to mental inactivity, paralysis, etc. As we are all outsiders, I feel we must proceed in any issues concerning living beings under the fixed assumption that our actions have the absolute potential to result in pain and suffering, exercising as much restraint and compassion as possible.
I also do not believe that plants are physically able to feel pain, or to suffer in the above physical sense. I am aware that their physiology dictates responses to physical needs for light and water, etc. but their physiology also lacks the necessary parts to result in a cause and effect synthesis in relation to a defence mechanism of pain (see above definition).