Frege-Geach problem

noun1

1. •
   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.