Halliday & Matthiessen (1999: 600):
What is common to these two further sources of insight [saying as well as sensing, and enacting as well as construing] is that both depend on projection.
(i) The potential for projecting is shared by sensing and saying; and when they are considered 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.
(ii) Projection also brings the ideational and the interpersonal aspects of consciousness together. Ideationally, projection is an mode of construal — in figures of sensing and saying, sensers and sayers construe meanings and wordings. Interpersonally, projection is an 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.