Grammatical meaning and situational meaning
First person certainties illustrate the distinction between grammatical meaning and situational meaning in an interesting way. Cf., ‘My name is NN‘, as said by NN. This utterance has grammatical meaning, but whether it also has situational meaning depends on the perspective we view it from. For the hearer this utterance supplies contingent information (at least, possibly). But that does not hold for the speaker. So, there is indeed a use for this sentence, –after all, this is typically the way in which we tell someone what our name is. But it has situational meaning only for the hearer, not for the speaker. The speaker needs a hearer to be able to use the sentence in the first place. And that distinguishes this sentence for its second and third person variants: ‘His name is NN‘ always has situational meaning. One could say that in the first person case the speaker uses the grammatical meaning to generate situational meaning for the hearer.