Halliday &
Matthiessen (2004: 441):
Metaphenomena — projections — can be associated only with certain types of process, essentially saying and sensing, plus in certain circumstances being; … . … Complication arises because the names of metaphenomena, nouns such as belief and fact, can sometimes enter into material processes where the metaphenomena by themselves cannot. … In other words, although projections cannot participate in processes other than those of consciousness, the names of projections can, because they can be used to label events or states of affairs.