Enhancing Hypotactic Verbal Group Complexes: Modulation Causative Passive

Halliday & Matthiessen (2004: 513):

Furthermore, causative have passives; so we can have:

(high) they were made/forced/required to accept
(median) they were got/obliged to accept
(low) they were allowed/permitted to accept

and this enables us to interpret modulation as it occurs within the verbal group:

(high) they are required to accept — they must accept
(median) they are obliged to accept — they should accept
(low) they are allowed to accept — they may accept