Halliday & Matthiessen (2004: 440-1):
[Consider] we saw that the boats had been turned. If I say I can see the boats turning, this is an event. A process ‘the boats are turning’ is being treated as a single complex phenomenon — a macrophenomenon … . If I say I can see that the boats are turning, this is a projection. The process ‘the boats are turning’ is being treated as the projection or idea of a phenomenon — a metaphenomenon, something not just bigger but of a different order of reality.