Disallow Self-Reference Loops
      
      Jim's claim is false.   
      
What About "anyone can say anything about anything"?
      Jim can say that some sentence references itself, 
      but we know he's lying or mistaken, just as if he'd said
      in(Eric, rm308) ∧ ¬ in(Eric, rm(308)).
      
It's like a listing of books, where some book has a
      checksum-invalid ISBN number.   Who will recognize that
      as an error; what will they do about it?   Can you say you have
      that book, in RDF?