16a Give the hat to whomever,
we also say,
16b Give the hat to whoever owns it,
16c 7 Give the hat to whomever owns it,
for in the first example whomever is the object of the preposition to, while in the second example whoever is the subject of the predicate owns and the entire clause "whoever owns it" is the object of the preposition to.
We noted that a predicate consists of a verb together with whatever adverbial modifiers and completions go with it. When the verb designates no real action, the complement may function simply to complete the subject by providing new information about it. These subjective completions comprise predicate adjectives and predicate nouns as in the following examples.
17a Justin is studious
17b Justin looks studious
17c Justin is a student
As long as we are not dealing with pronouns, such constructions are quite simple. The trouble with pronoun subjective completions is that, although we understand that they should logically be in the subject case, the instincts of word order incline us to prefer objective case forms, which is why you have to be taught not to write
18 7 It's me
and why Christ's question in the King James translation cited above as sentence 10 is properly termed hyper-correct, that is, so correct that it's wrong. The translator has too successfully resisted the desire to say:
19 Who do men say that I am?
where "who" is the subjective completion of "I am."