 Stalnaker’s response to this problem is to suggest that the context set for a belief report must be expanded so as to include worlds that correspond to the way that the believer himself (i.e. O’Leary) takes things to be. The diagonal proposition of the philosopher’s sentence is thus determined by considering what she would be saying if her sentence were asserted in contexts compatible with O’Leary’s beliefs (1987; 1988). However, there is no general rule for choosing which worlds are the relevant ones: