Material Clauses: Actor

Halliday & Matthiessen (2014: 224-5):

… ‘material’ clauses are clauses of doing–&–happening: a ‘material’ clause construes a quantum of change in the flow of events as taking place through some input of energy. … the source of the energy bringing about the change is typically a participant — the Actor … the ‘logical Subject’ of older terminology. The Actor is the one who does the deed — that is, the one that brings about the change.