Decide whether logical formula is a tautology
41223
How to check, whether the formula is a tautology
65379
Deriving $\neg R$ from $\{R↔(R∨(P∧¬P)), R↔¬P, ¬P→(P↔(Q→Q)), P→Q\}$
93544
Nested Quantifiers true or false
32027
Given (p ∧ q), use the Fitch system to prove (q ∨ r)
47222
Soundness of a rule of a proof system with respect to the truth tables?
138897
help with some Hilbert style proofs in a propositional logic axiom system.
134034
Is logic subjective?
31299
Using the Fitch system, how do I prove $((p \implies q) \implies p)\implies p$?
82739
Why is $\alpha \rightarrow \forall x(\alpha)$ not generally correct in first-order logic?
101163
Does there exist a universal formula of first-order logic that is satisfiable only by structures with infinite domains?
41622
Converting truth tables to boolean expressions
52585
How to prove that $[(p \to q) \land (q \to r)] \to (p \to r)$ is a tautology without using the truth table?
63963
deductive system where the axioms are all the propositions that are not tautology
91861
Propositional Logic: p → q, ¬p → r, ¬q → ¬r ⊢ q
72034
Truth table and the meaning of $\oplus$ in propositional logic
86248
Is $\exists x(x=a)$ a valid formula in first order logic with equality?
63952
Disproving: If $(\Gamma\vdash(\phi\,\lor\psi))$, either $(\Gamma\vdash\phi)$ or $(\Gamma\vdash\psi)$ is true