Halliday & Matthiessen (2004: 213):
In ‘relational’ clauses, there are two parts to the ‘being’: something is said to ‘be’ something else … This means that in a ‘relational’ clause in English, there are always two inherent participants … In contrast, the general classes of ‘material’ and ‘mental’ clauses have only one inherent participant (the Actor and the Senser, respectively).
