New posts in First Order Logic

How is "interpretation" used differently in propositional vs. first-order logic?

Why does Skolemming not preserve validity?

Forking but not dividing

Predicate Logic, Proof of validity . How to remove negation infront of existential quantifier?

Are these formal formulas equivalent?

How do I properly use a logical implication sign when solving an equation?

Is it possible to have two models $M$, $N$ and for each one an elementary embedding to the other one, but $M$, $N$ are not isomorphic?

With this definition of completeness, Gödel's Incompleteness result seems not surprising, so why it was back then?

Do we have to prove how parentheses work in the Peano axioms?

Advantages of finite axiomatizability