Material clauses represent “a quantum of change…unfolding through distinct phases” (H & M, p.184). This unfolding necessarily has an outcome: “a change of some feature of one of the participants” (H & M, p.184). This outcome may be either creative or transformative.
In a creative type of clause, the Actor (in an intransitive clause) or the Goal (in a transitive clause) “is construed as being brought into existence as the process unfolds” (H & M, p.184):
- Intransitive (What happened?) – Icicles formed.
- Transitive (What did they do?) – They built a house.
In a transitive type of clause, the outcome is “the change of some aspect of an already existing Actor (intransitive) or Goal (transitive)” (H & M, p.185):
- Intransitive (What happened to it?) – The icicles melted.
- (What did he do?) – He ran away.
- Transitive (What happened to it?) – The sun melted the icicles.
- (What did they do to him?) – They chased him away.
The outcome of the transformation is an (1) elaboration, (2) extension or (3) enhancement of the Actor or Goal. For examples, see here.
As for EFL, I think this creative/transformative distinction could also help make the whole transitive/intransitive a bit clearer for students by focusing not just on the process (for example, by having a long list of tansitive and intransitive verbs) but also demonstrating the function of the Actor and the Goal in the unfolding of the clause.