I have a question about Natural Deduction for Predicate Logic.
|-- Ǝx. ~P(x) ---> ~∀x. P(x) [ ~ = not ]
How about do you solve this, as I'm really getting a headache in figuring it out. The reason is that it contains no premises and just the conclusion, but my lecturer said it is solvable.
Does Ƚ can be assumed as ~∀x. P(x) (from ȽE)?