What is Sentience? From Definitions to Metaphors

Despite the growing interest in sentience, especially regarding sentience in non-human animals, there is little agreement around its evolutionary origin and distribution, ontological status or ethical relevance. One aspect of this work-in-progress situation is a panoply of definitions of sentience to be found in the literature, from intensional ones appealing to ontological features (such as awareness, agency, consciousness) to implicit extensional ones based on physiological, morphological or behavioural features. We review and classify some of the most common definitions of sentience to underline how they inevitably rely on pragmatical interests and ontological commitments which, when not explicitly declared, lead to pitfalls and fallacies when the definition is applied in practice. We claim that the obstacles, impasses and complications in the definition of sentience are consubstantial to its interest- and theory-laden, subjective nature. We suggest that, given these features, each definition should only be used in the limited epistemic and practical area it is produced for, while the general discourse around sentience is better developed through metaphorical rather than definitional language.