To articulate a sentence is to refer to the state of things spoken about; but this state of things is not, in general, completely symbolised by the sentence. To determine what we are talking about, it is necessary to take into consideration not only the sentence that one enunciates, but also the context of enunciation; and some elements in the sentence have precisely the effect of pointing out which aspect of the situation of enunciation must be considered to know what we are talking about.