I have the following sentence and diagram:
To sound intelligent on political issues was Wayne’s goal.
The infinitive phrase is the subject of the sentence. What is intelligent complementing exactly, sound? Is it a subjective complement since sound is intransitive?
Ok, so we are dealing here with:
An infinitive clause¹ (also called a nonfinite² infinitival clause) allows us to repackage information, more than a noun phrase can contain, and place it in the subject or object position of a clause. In the subject position, an infinitive clause is usually followed by some form of be or a static verb. It is uncommon to begin a clause with an infinitive clause, with a few exceptions such as dictionary definitions, quotes and poetic speech.
Infinitive phrase vs. infinitive clause — An infinitive structure, in traditional grammar, is called an infinitive phrase because it can not stand alone as a sentence (i.e., it does not have a subject and predicate). In contrast, in linguistic description, it is called an infinitival nonfinite clause because it typically does not have a subject and its verb form is not inflected for person, number or tense; also, the term "phrase" is reserved for word groups such as noun phrase, verb phrase, adjective phrase, verb phrase, etc.
So: To sound intelligent on political issues was Wayne's goal.
Why start the sentence with the infinitive? For emphasis.
That said: |to sound intelligent| is the subject. The predicate is |was|. And |Wayne's goal| is the subject complement (not object, as a be verb does not take objects).
Bear in mind that usually a sentence would be structured like this: Wayne's goal was to sound intelligent on political issues. In that case, |Wayne's goal| is the subject of the sentence, the predicate is |was| and |to sound intelligent| is the subject complement.
To sound intelligent on political issues is an infinitive phrase that functions as a noun and the subject in the sentence. The verb sound is a linking verb in the infinitive phrase, that is why the adjective intelligent is not a complement of this verb. So, there is no overt subject for the infinitive phrase in the sentence and the adjective intelligent can't be an overt complement of anything in the sentence. But, if we rearrange the sentence in for counstruction, It is a goal for Wayne to sound intelligent on political issues , it is possible to understand that the adjective intelligent is a so called implied complement of the noun Wayne in the possessive in the infinitive phrase to sound intelligent on political issues in the sentence. Or, the adjective intelligent is a complement by implication of the word Wayne.
