Sentience

Sentience is the ability to experience feelings and sensations. It may not necessarily imply higher cognitive functions such as awareness, reasoning, or complex thought processes. Some theorists define sentience exclusively as the capacity for valenced (positive or negative) mental experiences, such as pain and pleasure. Sentience is an important concept in ethics, as the ability to experience happiness or suffering often forms a basis for determining which entities deserve moral consideration, particularly in utilitarianism. The word "sentience" has been used to translate a variety of concepts in Asian religions. In science fiction, "sentience" is sometimes used interchangeably with "sapience", "self-awareness", or "consciousness".

Sentience in philosophy The term sentience was coined by philosophers in the 1630s for the concept of an ability to feel, derived from Latin sentiens (feeling). In philosophy, different authors draw different distinctions between consciousness and sentience. According to Antonio Damasio, sentience is a minimalistic way of defining consciousness, which otherwise commonly and collectively describes sentience plus further features of the mind and consciousness, such as creativity, intelligence, sapience, self-awareness, and intentionality (the ability to have thoughts about something). These further features of consciousness may not be necessary for sentience, which is the capacity to feel sensations and emotions.

Consciousness According to Thomas Nagel in his paper "What Is It Like to Be a Bat?", consciousness can refer to the ability of any entity to have subjective perceptual experiences, or as some philosophers refer to them, "qualia"—in other words, the ability to have states that it feels like something to be in. Some philosophers, notably Colin McGinn, believe that the physical process causing consciousness to happen will never be understood, a position known as "new mysterianism". They do not deny that most other aspects of consciousness are subject to scientific investigation but they argue that qualia will never be explained. In contrast, Daniel Dennett argues that consciousness isn't so rare and special, and that even bacteria possess some degree of consciousness. Regarding animal consciousness, in 2012 the Cambridge Declaration of Consciousness stated that many non-human animals possess the substrates of conscious states, and can exhibit intentional behaviors.[a] The declaration notes that all vertebrates (including fish and reptiles) have this neurological substrate for consciousness, and that there is strong evidence that many invertebrates also have it. Building on subsequent research, the New York Declaration on Animal Consciousness was issued in 2024. Signed by over 500 scholars, the declaration affirms "strong scientific support" for consciousness in mammals and birds and "at least a realistic possibility" of conscious experience in all vertebrates and in many invertebrates ("including, at minimum, cephalopod mollusks, decapod crustaceans, and insects"). The declaration goes beyond pure scientific description to make an ethical argument: that where a realistic possibility of conscious experience exists, it is irresponsible to disregard this in decisions affecting those animals.

Phenomenal vs. affective consciousness David Chalmers argues that sentience is sometimes used as shorthand for phenomenal consciousness, the capacity to have any subjective experience at all, but sometimes refers to the narrower concept of affective consciousness, the capacity to experience subjective states that have affective valence (i.e., a positive or negative character), such as pain and pleasure.

Sentience quotient The sentience quotient concept was introduced by Robert A. Freitas Jr. in the late 1970s. It defines sentience as the relationship between the information processing rate of each individual processing unit (neuron), the weight/size of a single unit, and the total number of processing units (expressed as mass). It was proposed as a measure for the sentience of all living beings and computers from a single neuron up to a hypothetical being at the theoretical computational limit of the entire universe. On a logarithmic scale it runs from −70 up to +50.

Eastern religions

Eastern religions including Hinduism, Buddhism, Sikhism, and Jainism recognise non-humans as sentient beings. The term sentient beings is translated from various Sanskrit terms (jantu, bahu jana, jagat, sattva) and "conventionally refers to the mass of living things subject to illusion, suffering, and rebirth (Saṃsāra)". It is related to the concept of ahimsa, non-violence toward other beings. In Jainism, many things are endowed with a soul, jīva, which is sometimes translated as 'sentience'. Some things are without a soul, ajīva, such as a chair or spoon. There are different rankings of jīva based on the number of senses it has. Water, for example, is a sentient being of the first order, as it is considered to possess only one sense, that of touch. Sentience in Buddhism is the state of having senses. In Buddhism, there are six senses, the sixth being the subjective experience of the mind. Sentience is simply awareness prior to the arising of Skandha. Thus, an animal qualifies as a sentient being. According to Buddhism, sentient beings made of pure consciousness are possible. In Mahayana Buddhism, which includes Zen and Tibetan Buddhism, the concept is related to the Bodhisattva, an enlightened being devoted to the liberation of others. The first vow of a Bodhisattva states, "Sentient beings are numberless; I vow to free them." In traditional Tibetan Buddhism, plants, stones and other inanimate objects are described as possessing spiritual vitality or a form of 'sentience'.

Animal welfare, rights, and sentience

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