Is there an axiomatic system for (classical) propositional logic that does not use modus ponens as a (primitive) rule?
I would be particularly interested in a derivation of it from some other set of rules. I would assume that this is possible with rules only for, e. g., $\wedge$ and $\neg$, but I've never seen it done before.
$${a\rightarrow b}\vdash \neg a\vee b\quad\mbox{and}\quad {a, \neg a\vee b}\vdash b.$$ And the first of those can be completely ignored if we agree to treat "$a\rightarrow b$" as an abbreviation for "$\neg a\vee b$" in the first place. Does that count?
– Noah Schweber Feb 23 '22 at 05:07