The official definition of ‘pain’ by the International Association for the Study of Pain (IASP) hasn’t seen much revision since its publication in 1979. There have been various criticisms of the definition in the literature from different quarters: that the definition implies a dubious metaphysical dualism, that it requires a strong form of consciousness as well as linguistic abilities, that it excludes many vulnerable groups that are otherwise perfectly capable of experiencing pain, that it has therefore unacceptable practical as well as ethical consequences, that it is unhelpful to the health-care professional as an operational definition, that it is too narrow, and many others. In my view, most of these criticisms depend on misunderstand...