query: Logic justification for the use of "Let $y = ...$" in Existential proof.
positive_passages.docid: 148790
positive_passages.text: Basic question about proofs with the goal $\exists x P(x)$
negative_passages.docid: 45481
negative_passages.text: Prove or disprove validity: $(\forall x \exists y (P(x) \supset Q(y))) \supset(\exists y \forall x (P (x) \supset Q(y)))$
negative_passages.docid: 41182
negative_passages.text: What does the construct x = x || y mean?
negative_passages.docid: 126870
negative_passages.text: Show that axiom of replacement implies from the Axiom of Specification [Proof Verification]
negative_passages.docid: 143248
negative_passages.text: What approach should I take to establish this logical proof?
negative_passages.docid: 148239
negative_passages.text: natural deduction proof with De Morgan's laws
negative_passages.docid: 140682
negative_passages.text: Proving a property of a Logic Formal Language
negative_passages.docid: 32244
negative_passages.text: Propositional Logic - Deduction
negative_passages.docid: 96504
negative_passages.text: First-Order Logic vs. Second-Order Logic
negative_passages.docid: 28281
negative_passages.text: Different standards for writing down logical quantifiers in a formal way
negative_passages.docid: 102202
negative_passages.text: The smallest infinity and the axiom of choice
negative_passages.docid: 17073
negative_passages.text: Using proof by contradiction vs proof of the contrapositive
negative_passages.docid: 6535
negative_passages.text: Proof of for-all / there-exists "negation"?
negative_passages.docid: 96904
negative_passages.text: Predicate Calculus Practice
negative_passages.docid: 9493
negative_passages.text: While proving a universal quantification, we begin by "Let ... in ..." or "Arbitrary choose ..."?
negative_passages.docid: 94617
negative_passages.text: Showing Consistency and Completeness implies a unique truth assignment
negative_passages.docid: 141952
negative_passages.text: Is there a decision procedure for intuitionistic propositional logic?