Suppose there is an Internet Community with just one moderator; and that every person in the community keeps himself moderated: some by moderating themselves, some by obeying the (one and only) moderator.
It seems reasonable to imagine that the moderator obeys the following rule:
He moderates all and only those members of the community who do not moderate themselves.
Under this scenario, we can ask the following question:
– Does the moderator moderate himself?
Asking this, however, we discover that the situation presented is in fact impossible:
If the moderator does not moderate himself, he must abide by the rule and moderate himself.
If he does moderate himself, according to the rule he will not moderate himself.