Negation of for every and there exist statements
6535
Proof of for-all / there-exists "negation"?
27475
"Every" vs "each" usage
22584
Can we prove that a statement cannot be proved?
5293
Show that the logic $ \ \forall x \exists y \ P(x,y) \ $ is not logically equivalent to $ \ \exists x \forall y \ P(x,y) \ $
148028
Are there statements that are undecidable but not provably undecidable
20658
Difficulty in finding a counterexample
93651
Difference between "each" and "every"
30733
Negation as failure in Prolog is a procedural behavior?
125317
Is this statement "Every element in the empty set is greater than itself." true or its negation is true?
49414
Negation in English
6166
Is the following statement provable?
103483
How can this English sentence be translated into a logical expression? ( Translating " unless")
99480
Why is predicate "all" as in all(SET) true if the SET is empty?
17966
Representing the statement using Quantifiers
45481
Prove or disprove validity: $(\forall x \exists y (P(x) \supset Q(y))) \supset(\exists y \forall x (P (x) \supset Q(y)))$
49385
Proving $\forall x (A\to B) \to(A \to \forall x B):x\notin \mbox{free}(A)$ in a Hilbert system where it is not an axiom
67683
Building logical criteria (with AND , OR, etc)