A barber shaves all the men in a village who do not shave themselves.
So who shaves the barber?
If the barber shaves himself, then he belongs to the subset of men who are not shaved by the barber.
If he does not shave himself, then the barber does.
As nonsensical as any result seems, this is the kind of thing that theoretical mathemeticans, philosophers and others puzzle over. It gets at the heart of the question:
Does everything exist? If not “here,” then somewhere?
If not, then why does only whatever is out there exist? What governs the circumstances under which whatever is, is?