Misunderstanding The Complement vs Adjunct Distinction

Martin, Matthiessen & Painter (2010: 72-3):

The Complement is in a complementary role to the Subject; that is, it has the status of 'potential Subject'. That potential could be realised if the voice of the clause were active rather than passive or vice versa. As a potential Subject, the Complement is realised by a nominal group, while an Adjunct is realised by a prepositional phrase or adverbial group: 

The first Complement in the above examples also has the experiential role of Beneficiary. This particular experiential role can also be realised later in the clause in a prepositional form, as shown below: 

In its prepositional form a Beneficiary is treated as an Adjunct in IFG, on the grounds that it cannot be a Subject in this form. Nonetheless some analysts would argue for regarding it as a Complement here too. Although to Linda or for my father is not a potential Subject, his mum or Linda does have the potential for becoming Subject without the preposition remaining in the structure:

Linda wasn't told that by him.

My father is being made a cup of tea by Angela in the kitchen.

Sharon may be sold the car at a cheap price by them.

His mum will be sent some flowers by him at Christmas. …

A similar argument applies to a by __ phrase which fills the experiential role of Agent, as in Linda will be told that by Peter or His mum will be sent some flowers by him. In IFG these are treated as Adjuncts, indicating that when agency is expressed in this form it has a more peripheral status than when it is mapped on to the interpersonal Subject role, as in He will send his mum some flowers.

Blogger Comments:

To be clear, "some analysts" include Martin, but not Matthiessen, and his view involves a very simple misunderstanding. To explain:

On the one hand, Beneficiaries and Agents realised by prepositional phrases, such as for my father and by Peter fulfil the Halliday's criterion for Adjunct, in that they are not potential Subjects.

On the other hand, however, what is a potential Subject, in such cases, is the minor Complement of the prepositional phrase serving as Adjunct. Halliday & Matthiessen (2014: 155):

A prepositional phrase, however, has its own internal structure, containing a nominal group serving as Complement within it. In by the duke, the duke is a Complement with respect to the preposition by (which serves as a Predicator). So, although by the duke is itself an Adjunct, and could not become Subject, it has as one of its constituents the duke, which is a Complement at another rank, and could become Subject.