The Dog in the Manger is an historical
morality tale, sometimes claimed for
Aesop, of a
dog who (naturally, being a
carnivorous canine type of beastie) is able to take no enjoyment from eating
grain. But the dog of this story naetheless sits in a manger full of grain -- and threatens off other animals (
oxen, in most retellings,
horses in some,
sheep or
goats in a few). The term for some time was in
vogue as an
idiom used to refer to somebody who wished to
prevent others from enjoying something while having no interest in self-enjoyment of that thing either.
Though the phrase is most analogous to
defense against the use of an existing finite resource -- for example the ardent
bicyclist who would ban the burning of
fossil fuels -- it may be used as well for
inexhaustable metaphorical concepts -- for example the ardent
prude who has no interest in
pornography, but would wish to ban those who have such an interest from viewing such materials.