Halliday & Matthiessen (1999: 152):
Sensing is clearly modelled as a process of human consciousness, with the Senser as a human being — so much so that merely coming to occupy that rôle is sufficient to endow the participant in question with human-like consciousness. The Phenomenon, on the other hand, is given a somewhat ambivalent status: in one of its guises (as in [emanating] Do you like those colours?) it seems to be just part of the environment; but in its other guise (as in [impinging] Do those colours please you?) it seems to be playing a more active rôle.