Can they suffer? How sentience became the test for moral concern
Jeremy Bentham argued that what matters about an animal is not whether it can reason or talk, but whether it can suffer. That question about sentience, the capacity to feel, now shapes animal welfare law, fuels debates over fish and insects, and raises new puzzles about artificial minds.
Philosophers coined the word in the 1630s from the Latin for feeling. Some define it narrowly as the ability to have good or bad experiences such as pleasure and pain, while David Chalmers notes it can also mean having any subjective experience at all. Thomas Nagel's essay What Is It Like to Be a Bat? framed consciousness as there being something it feels like to be a creature. Colin McGinn doubts we will ever explain that inner feel, whereas Daniel Dennett thinks even bacteria have a sliver of consciousness.
Scientists have steadily widened the circle. The 2012 Cambridge Declaration held that all vertebrates, fish and reptiles included, have the brain machinery for conscious states. A 2024 New York declaration signed by over 500 scholars found strong support for consciousness in mammals and birds and a realistic possibility in all vertebrates and many invertebrates, including octopuses, crabs and insects. Fish were long dismissed as reflex machines lacking a neocortex; one researcher links that belief to a 1980s fight over banning catch and release.
How can pain be detected in another creature? Many animals, even insects, have nerve sensors that register harm, but researchers look for more. A dog that limps, licks its wound, avoids the spot where it was hurt and accepts painkillers gives good reason to think it truly feels something. Willingness to endure pain for a big enough reward also suggests more than reflex.
Law and religion have long engaged the idea. In 1997 the European Union wrote animal sentience into its treaties. Jainism ranks souls by their number of senses, placing water in the first order with touch alone, and a Bodhisattva's first vow promises to free numberless sentient beings.
Source: Sentience
