New posts in Predicate Logic

Is this equivalence of the compactness theorem true?

Is the "ancestor" relationship impossible to define in first-order logic?

What exactly is a contradiction and how does it differ from falsity?

The constraints of Universal Introduction in logic proofs

Why is this natural language sentence converted into a predicate logic language the way it is here?

Everyone loves all lovers, Romeo loves Juliet $\vdash$ I love you (Natural deduction proof)

Definability in the signature of first-order logic with identity

Negated Existential Quantifier of a conjunction

Why is $\exists y \in B, \ \forall x \in A, \ P(x,y) $ stronger than $\forall x \in A,\ \exists y \in B, \ P(x,y)$

Why is the negation of the statement $\exists x P(x)$ given by $\forall x (\neg P(x))$ and not $\not \exists x P(x)$?