here we go: shaves(barber, X) :- male(X), not shaves(X,X).
   male(barber). He both shaves and does not shave himself by
   definition. Here is the issue with the paradox: It is that it is
   incomplete. It may be a complete statement for logic, but it is
   only a paradox because of the constraints of logic. One of the
   constraints of logic is that there is no time-scale. The system
   needs more inputs. The definition can exist - we just made it.
   We defined it. But to resolve it we need to: a) specify times
   where he does shave himself. b) specify times where he does not
   shave himself. It is that he is both shaving and not shaving
   himself SIMULTANEOUSLY (and _this_ is where the issue arises
   from - the simultaneousity _implied_ in the system) - that it
   becomes a paradox *within* the constraints of non-contradictory
   logic _only_. In short, it is a sign that you have reached the
   border. You have reached the limits of what non-contradictory
   logic is capable of. It can go no further. So, one must go
   further via other means. Add time. Add other additional metrics,
   such as statistical probability. Provide a choice for the Actor.
   Provide a choice for the person solving the puzzle. [does he
   shave today or does he not?] etc. Additionally, one very
   important, easy to overlook fact: This is a thought experiment.
   A thought experiment is a fiction. There is no barber that
   exists with this definition.