Halliday & Matthiessen (1999: 583):
A projection mental clause such as I (don’t) think, since ideationally it realises a figure of sensing, construes the speaker as ‘Senser at the time of speaking’ (it occurs metaphorically only in the present tense); at the same time, it enacts the speaker’s own ‘intrusion’ into the dialogue — his or her judgement about how much validity can be attached to the proposition contained in the projected clause. Interpersonal metaphor is thus the hinge between the ideational and the interpersonal modes of constructing the self.