theorem
  Top VarPoset = {}
proof
  set V = the set of all varcl A where A is finite Subset of Vars;
A1: {} Vars in V by Th8;
A2: VarPoset opp is lower-bounded by YELLOW_7:31;
  (Bottom InclPoset V)~ = {} by A1,YELLOW_1:13;
  hence thesis by A2,YELLOW_7:33;
end;
