In a certain town, there are the following regulations concerning the town barber: Anyone who does not shave himself must be shaved by the barber. Whomever the barber shaves, must not shave himself. Show that no barber can fulfill these requirements. That is, formulate the requirements as sentences of FOL and show that in any interpretation where the first regulation is true, the second one must be false. (This is called the barber's paradox and was formulated by Bertrand Russell.)