I'm trying to use those [Logical equivalence](https://en.wikipedia.org/wiki/Logical_equivalence) as axioms to prove some [PL](https://en.wikipedia.org/wiki/Propositional_calculus) statements,<br> In this case I followed the examples in the documentation that didn't use the build-in logic functions$\{\text{And}[,],\text{Or}[,],\text{etc}\}$, the reason is, otherwise it will evaluate some axioms as True. Here is my code: (Updated) PL = {ForAll[{p, q, r}, and[p, or[p, not[p]]] == p], ForAll[{p, q, r}, or[p, and[p, not[p]]] == p], ForAll[{p, q, r}, or[p, or[p, not[p]]] == or[p, not[p]]], ForAll[{p, q, r}, and[p, and[p, not[p]]] == and[p, not[p]]], ForAll[{p, q, r}, or[p, p] == p], ForAll[{p, q, r}, and[p, p] == p], ForAll[{p, q, r}, not[not[p]] == p], ForAll[{p, q, r}, or[p, q] == or[q, p]], ForAll[{p, q, r}, and[p, q] == and[q, p]], ForAll[{p, q, r}, or[or[p, q], r] == or[p, or[q, r]]], ForAll[{p, q, r}, and[and[p, q], r] == and[p, and[q, r]]], ForAll[{p, q, r}, or[p, and[q, r]] == and[or[p, q], or[p, r]]], ForAll[{p, q, r}, and[p, or[q, r]] == or[and[p, q], and[p, r]]], ForAll[{p, q, r}, not[and[p, q]] == or[not[p], not[q]]], ForAll[{p, q, r}, not[or[p, q]] == and[not[p], not[q]]], ForAll[{p, q, r}, or[p, and[p, q]] == p], ForAll[{p, q, r}, and[p, or[p, q]] == p]} proof = FindEquationalProof[ ForAll[{p, q, r}, not[or[and[and[p, q], not[p]], and[not[and[p, q]], p]]] == or[not[p], q]], PL] proof["ProofGraph"] proof["ProofNotebook"] I just fixed the typo in the axiom, yet trying to let it prove that statement: $$\neg(((p\land q)\land \neg p)\lor(\neg(p\land q)\land p))\equiv\neg p \lor q$$ not[or[and[and[p, q], not[p]], and[not[and[p, q]], p]]] == or[not[p], q]] But seems not work, i tried shorter ones, which works fine, is it because this statement too long or something I missed $?$ Any help would be appreciated. I added last two axioms from Logical equivalence: ForAll[{p, q, r}, or[p, not[p]] == True], ForAll[{p, q, r}, and[p, not[p]] == False] Seems works now. And $1-4$ can also changes to: ForAll[{p, q, r}, and[p, True] == p], ForAll[{p, q, r}, or[p, False] == p], ForAll[{p, q, r}, or[p, True] == True], ForAll[{p, q, r}, and[p, False] == False]