Extending Hypotactic Verbal Group Complexes: Potentiality Causative

Halliday & Matthiessen (2004: 512):

Here there are causative forms as follows:

(1) potential: the patient can see clearly

causative: this enables the patient to see clearly

(2) achieval: John learnt to fly

causative: Mary taught John to fly

Again, these causatives have passives: the patient is enabled to see clearly, John was taught to fly by Mary.