I've been beating my head trying to prove the following tautology for some time:
$$ \therefore \neg \forall{x} \exists{y} (Py \wedge \neg Px)$$
I think there's some tricky intermediate step that I'm missing. Any help would be appreciated.
I've been beating my head trying to prove the following tautology for some time:
$$ \therefore \neg \forall{x} \exists{y} (Py \wedge \neg Px)$$
I think there's some tricky intermediate step that I'm missing. Any help would be appreciated.