15-317 Constructive Logic
Lecture 11: Classical Quantification
In this lecture we finish the discussion of classical logic
by exploring the consequences of the law of excluded middle on
quantification. We note that the quantifiers are now dual,
and each can be defined in terms of the other using negation.
Existential quantifiers can be proved without supplying a witness,
which means that the computational interpretation of classical
propositional logic does not extend to quantifiers.