The story
Named after Peter Geach and Gottlob Frege; Geach developed the concept from Frege's writings.
Etymology from Wiktionary, CC BY-SA 4.0.
Frege-Geach problem
Today it means: The problem that, by subscribing to expressivism, one accepts that the meaning of (say) "it is wrong to tell lies" is different from the meaning of the "it is wrong to tell lies" part of the conditional "if it is wrong to tell lies, then it is wrong to get your little brother to lie", and that therefore expressivism is an inadequate explanation for moral language. Full definition →