% problem-set/pelletier/p39.clauses
% created : 08/17/89
% revised : 08/17/89

% description:
%
% Full Predicate Logic (without Identity and Functions). Problem #39.
% Russell's paradox: there is no `Russell set' (a set which contains exactly
% those sets which are not members of themselves)
% -(Ex)(Ay)(Fyx <-> -Fyy).
 
% representation:
%
% declare_predicate(2,F).
% declare_constant([a]).
% declare_variables([x,y,z]).


% denial of the statement
(exists x all y (F(y,x) <-> -F(y,y))).