Most English verbs have existential entailments in the following sense:
In logic, the first translation entails the second:
In logic, the two
sentences have the same translation:
Even more simply:
In logic, again, the first translation entails the second:
The following existential entailment also holds:
In logic, the first translation again entails the second:
You can think of existential entailment as semantic obligatoriness. Eating can't go on without something filling both the eater and the eaten roles. But remember: existential entailment is quite different from syntactic obligatoriness:
(i) John devoured the apple.The verb devour has an existential entailment on the direct object position. And, independently of that, that second argument position is obligatory.
(ii) John devoured something.
(iii) * John devoured.
Not every verb gives an existential entailment for every argument position:
Because of this, it's not clear how to translate John is looking for a unicorn into predicate logic. This translation