Theme Identification vs Theme Predication

See Halliday & Matthiessen (2014: 94, 124, 198).

Thematic Equative In Complex With Nested Dependent Clause

This identity encodes the Value what we can notice by reference to the Token a clear evolutionary tendency towards centralisation.

Thematic Equatives

 

See Halliday & Matthiessen (2014: 93-6).

One reason why the nominalisation in a thematic equative always serves as the Value participant is that an identifying clause relates a lower level of abstraction, Token, to a higher higher level of abstraction, Value, and the meaning realised by a nominalisation is, ceteris paribus, of a relatively higher level of abstraction than the meaning realised by a non-nominalisation.