Exercise 1858Logic, sets and proofs › Quantifiers and negationL1Added 3 Nov 2026
Scope of quantifiers
#scope#quantifiers#ambiguity
Statement
Explain the difference between:
- : ;
- : .
Hint
Consider whether depends on .
Show solutionHide solution
Solution
. : if all satisfy , then . Here does not depend on ; the quantifier applies only to .
. : for every , if then . Each implication is quantified separately.
Example. : " is a counterexample"; : "the conjecture is false". : "if all are counterexamples, the conjecture is false". : "every counterexample makes the conjecture false".
Conclusion. Scope matters: and differ in meaning.