Halliday & Matthiessen (1999: 600):
The potential for projecting is shared by sensing and saying; and when they are construed together, they reveal a very powerful principle that is embodied in the folk model: that through projection, we construe the experience of ‘meaning’ — as a layered, or stratified phenomenon, with ‘meanings’ projected by sensing and ‘wordings’ projected by saying. … Interpersonally, projection is a mode of enactment — in moves in dialogue, interactants enact propositions and proposals. Interpersonal metaphors of mood and modality bring out the relationship between the two: here interactants simultaneously both enact propositions and proposals interpersonally and construe this enacting in such a way that the ideational construal comes to stand as a metaphor for aspects of the interpersonal enactment.