The Existential Quantifier

• ∃ means there exists.
• ∃ x (swan(x) -> -white(x)) this means there exists a swan that's not white. It contradicts the earlier statement.
• You can combine this with the universal quantifier.
• ∀ y (∃ x (mother(x,y))).
• This means that everyone has a mother.
• How would you write Chris' mother is not alive?