  Geach thought that the second and third desiderata would be especially hard to accomplish simultaneously. Normally we believe that the status of an argument as valid depends, at least in part, on the words not shifting in meaning as we move from premise to premise. But the simplest story of the meaning of moral terms, that they are devices for expressing pro and con attitudes, seems then to require that they mean something else when embedded in the antecedents of conditionals. Consider the following example from Geach (1965, 463):