Can monadic second-order logic characterize finiteness?
108533
Is there any formula of monadic second-order logic that is only satisfied by an infinite set?
74455
Can a single sentence be used to distinguish between isomorphic classes of finite structures?
67490
Restricing domains for universal and existential quantifiers
16187
proof of functional completeness of logical operators
53056
natural deduction: introduction of universal quantifier and elimination of existential quantifier explained
57089
Class of functions computable by Coq
45792
Rigorous proof that surjectivity implies injectivity for finite sets
153652
Countable ordinals are embeddable in the rationals $\Bbb Q$ -- proofs and their use of AC
72371
Proof of Strong Induction Using Well-Ordering Principle
156178
Do counit-unit adjunctions have the expected universal properties?
93040
$f$ is surjective iff it has a right inverse: using the axiom of choice and errors in ProofWiki
94617
Showing Consistency and Completeness implies a unique truth assignment
52451
Ordered Triples and Set Theory
82739
Why is $\alpha \rightarrow \forall x(\alpha)$ not generally correct in first-order logic?
91861
Propositional Logic: p → q, ¬p → r, ¬q → ¬r ⊢ q
85398
$\mathsf{ZF}$ is not finitely axiomatizable
53199
First-Order Logic: Formalisation of the phrase "Not all that glitters is gold"