In Areopagitica — a work of prose — Milton choses to capitalize words in a seemingly arbitrary manner, though his use of capitalization isn’t arbitrary at all but a calculated, stylistic approach to convey a sense of individuality in something that would normally be lumped with a broader population of (for lack of a better term) “things” that have a shared characteristic, and, paradoxically, he is also conveying a sense of generality.
For example, when Milton writes about what should not be representative of liberty in an effort to inversely posit what should be representative of liberty, he writes:
“For this is not the liberty which wee can hope, that no grievance ever should arise in the Commonwealth, that let no man in this World expect; but when complaints are freely heard, deeply…”
If Milton were to have omitted the identifier “this” from the clause, “World” would have stood as its own form and would have been expressive of a particular place (i.e. a proper noun). “World” could have been another form of “Earth,” the primary way we identify our planet. Instead, he does add “this.” Milton is aware of the grammatical change when adding an identifier, but he does it anyway, betraying modern conventional writing standards (though he is not modern). Again, he’s emphasizing the word. It stands out.
He is also conveying a sense of generality. To him, there are other worlds mythologically, religiously, and secularly. But, by emphasizing the “w” he’s toying with proper nouns while including an identifier, thereby intimating generality and individuality all at once.
For Mil’ run of the mill, but for us not. Nice job tons.