I am a student learning mathematical logic as a hobby. When I say "zeroth order" I mean "not predicate logic".
Question: Is it possible to convert a categorical proposition into a zeroth-order proposition?
For example: If I have a categorical proposition "All $S$ are $P$", then can I construct an implication that says "If an object is $S$, then the object is $P$"?
If this is possible, then is there a specific replacement rule for accomplishing this? Does the replacement depend on whether the categorical proposition is $A$, $E$, $I$, or $O$?
"All $S$ are $P$" is translated in modern logic exactly as "For every $x$, if $x$ is $S$ then $x$ is $P$", i.e. as $∀x(Sx → Px)$.
Categorical propositions are part of the theory of Syllogism. In modern terms, it is part of an interesting fragment of predicate logic: the so called monadic predicate calculus.
But regarding the title question, the answer is: no.
In propositional logic we can have $S → P$ and $S ∧ P$, but we cannot express the difference between "all" and "some".