Does this show that the statement "I have a toothache" is true for smith but not true for Jones? Not at all: it means only that the proposition "Smith has a toothache" is true, and the proposition "Jones has a toothache" is false. we must remember that the word "I" refers to a different person every time it is used by a different speaker; when Smith says "I" he means Smith, and when Jones says "I" he means Jones. Once this is clear, we can see that the sentence "I have a toothache" expresses a different proposition when Smith utters it from when Jones utters it. And since it expresses two different propositions, it is no surprise that one of these propositions is true and the other false.