Objects

[Koirake]

I've been reading this book by this Ed Finegan guy who works at the college of southern CA which claims the direct object is simply the noun phrase that follows immediately after a verb. So in

"He is a swimmer" is "swimmer" direct object?

On this here website, y'all define direct object differently in the glossary. :\ Sounds like maybe there are so many different views about it that there is no telling which one of them is correct.

And what about indirect objects and obliques? The same book claims an oblique is the object of a preposition, then contradicts itself later by equating 'him' in 'I gave the book to him' with an indirect object. Is it an oblique or is it an indirect object? It's clearly the object of a preposition.
Though if we perform some dative movement on the sentence, turning it into 'I gave him the book', then 'he' is no longer the object of a preposition. So has its syntactic role changed? In this case 'him' would, by definition, be direct object since it immediately follows the verb. Which of course seems ridiculous.

So must one just conclude that scholars differ on what direct objects, indirect objects and obliques (if they use such a term at all) are, and that one mustn't bother trying to learn these things because no matter which view you pick, it will be wrong to most grammarians?

[Tdol]

That is not the direct object here as the verb is a copular (or linking) verb, and such verbs don't take direct objects. It is, in fact, the subject complement. The noun phrase after a verb is often the direct object, but not always. For instance, with a ditransitive verb, you could have 'I wrote John a letter, but the direct object is 'a letter', not 'John'.