It’s been a while, but I recall a comment I was about to make when the subthread was shut down: That the use of “argument” seems overbroad.
In logic, there is a distinction between concepts, propositions, and arguments. A concept has a definition, which is a proposition; a proposition has a proof, which is an argument.
Now, if we’re talking about literature, literary works do have themes, the things they are “about.” A theme is a topic that the content of the work relates to and that ties it all together. For example, the theme of the Odyssey is polytropia (a double theme, in this case, as Odysseus is polytropos both in the passive sense, being repeatedly led astray in his long journey home, and in the active sense, being a man of lies and stratagems); the theme of Dracula is redemption. A topic is a concept. But not every literary work has a thesis (there is such a thing as a roman à thèse, but not all novels are that); not every literary work asserts a specific proposition. We may be able to say “the theme of X is a,” but not “the theme of X is that P.”
I think it’s even rarer that a literary work has an argument. There are examples; Andrew Marvell’s “To His Coy Mistress” is presented in the form of a syllogism: “If we had unlimited time we would not need to consummate our love; we do not have unlimited time; therefore we need to consummate our love” (though logically that’s not a valid syllogism!). But even a work with a thesis may not present an attempted proof of that thesis; it may simply assert it. And all the more, a work with a theme may not even make a specific assertion about that theme, let alone providing an argument for one.
(And once we get out of literature into other arts, the concept of “argument” becomes even harder to apply. The Fifth Brandenburg Concerto has a theme, but it’s a series of musical notes with certain durations and pitches; it’s not something that can be verbally expressed as a concept. I really don’t see how it could be said that it asserts a proposition about that theme, or presents an argument for it. This whole system of ideas seems to be applicable to art in the medium of language, but not to art in other media such as imagery or sound or bodily movement.)