Are all living things sentient beings?
- According to the non-profit Animal Ethics, a being must meet three different criteria to be classified as “sentient”: it must exhibit behavior based on avoiding “what threatens [its] survival and seek[ing] what promotes it,” it must have evolutionary markers such as being “complex and adaptable to circumstances,” and it must have the “presence of a centralized nervous system.”
- A driving force behind animal rights activism, sentiocentrism is defined as an “ethical view which places sentient individuals (i.e., basically conscious beings) at the center of moral concern. Both humans and other sentient individuals have rights and/or interests that must be considered.”
- Harvard psychology professor, Marc Hauser, believes that animals have interesting thoughts but that they are limited by not utilizing speech as a means to communicate. He says, “When humans evolved speech, they liberated the kinds of thoughts non-humans have. Feedback between language and thinking then boosted human self-awareness and other cognitive functions.”
- In 2012, neuroscientists and animal experts at Cambridge’s Francis Crick Memorial Conference publicly proclaimed The Cambridge Declaration on Consciousness in Non-Human Animals, which essentially stated that animals besides humans are also conscious.
According to Buddhist philosophy, humans are sentient beings that possess awareness characterized by five key components or skandhas; matter, sensation, perception, mental formations, and consciousness. Therefore, it would take these particular aggregates for a living thing to be classified as a sentient being.
Plants and simple creatures like insects, for example, do not meet these criteria. Critics of the 'plant consciousness' movement reference 'the unique and remarkable degree of structural, organizational, and functional complexity that the animal brain had to evolve before consciousness could emerge.' And although researchers admit that there need to be more studies done on the potential for consciousness in invertebrates, they conclude that it is 'unlikely for invertebrates to possess cognitive sophistication, mood state behaviors, and motivational tradeoffs.' In other words, bugs react; they don't necessarily think.
The ability to alter behavior based on experience is indicative of sentience. While certain entities may react to stimuli, this phenomenon is not the same as experiencing pain or pleasure through a nervous system and producing a sentient response.
All life should be respected and not harmed unnecessarily, but that is not to say that all living things are sentient beings. Plants are alive, but they don't have wants, desires, or preferences. It is in our best interest to water them because we don't want them to die, but plants don't suffer existential dread when faced with a drought. Yet pigs are aware that they are about to be slaughtered.
A distinction can be clearly drawn between things that are alive and those that are sentient.
The word sentient is defined as 'having the power of perception by the senses; conscious.' Taking this definition into account, all living organisms are sentient, even if they don't all share the same ways of perceiving the world.
Let's start with organisms close to us—in the animal kingdom. Animals have been proven to feel emotions, even complex ones like love. In 2015 a male swan from Limpopo Zoo in Russia lost his partner and began isolating himself from the rest of his group. He became lethargic and stopped eating. In humans, those are classic signs of depression. Eventually, the swan died—and some would argue of 'heartbreak.' Jane Goodall observed the same responses in chimpanzees who lost their mothers.
A study from the University of Wisconsin showed that plants demonstrate flight-or-fight reactions using a nervous-system type signal similar to animals' pain responses. Although these responses cannot be attributed to fear—as fear arises from a nervous system—they are nonetheless the plants' version of that emotion. The study showed that a plant released glutamate around an injury, leading to a calcium wave rushing through its body, preparing other plant areas to defend themselves.
Plants have different priorities from animals and humans, and their sensory system reflects this. It's important to remember that the human species isn't a baseline for what sentience is. In a way, plants feel and perceive better than humans, as some species have eleven types of photoreceptors, giving them better vision than most animals. But that doesn't make other creatures less sentient. It means they are sentient in their own ways.