This and the related words painism and painience are creations of Dr Richard Ryder, a British psychologist and ethicist, a retired professor and former chairman of the RSPCA. He has a long-standing concern for animal rights — he claims to have coined speciesism in the 1970s to refer to what he called in 1975 “the widespread discrimination that is practised by man against other species”.
He made painient and painience from pain by analogy with sentient and sentience, so that painient means being able to feel pain, while painience is the quality or state of being painient. Painism is his term for the moral theory that requires us to reduce the pain of others who suffer the most, especially that of individuals.
All three words have been known since the middle 1990s, though they remain rare. Painism gained attention in 2001 through his book Painism: A Modern Morality; in it he argues that anything that can feel pain can suffer and so must have rights, specifically in the case of animals to be protected from human use and abuse.
He wrote recently in a newspaper article: “Our concern for the pain and distress of others should be extended to any ‘painient’ being regardless of his or her sex, class, race, religion, nationality or species. Indeed, if aliens from outer space turn out to be painient, or if we ever manufacture machines who are painient, then we must widen the moral circle to include them.”