set FV = { [[A,B],f] where A, B is Element of V, f is Element of Funcs V : ( ( B = {} implies A = {} ) & f is Function of A,B ) } ;
consider A being Element of V;
now set f =
id A;
take m =
[[A,A],(id A)];
m in { [[A,B],f] where A, B is Element of V, f is Element of Funcs V : ( ( B = {} implies A = {} ) & f is Function of A,B ) } A1:
(
A = {} implies
A = {} )
;
then
id A in Funcs V
by Th1;
hence
m in { [[A,B],f] where A, B is Element of V, f is Element of Funcs V : ( ( B = {} implies A = {} ) & f is Function of A,B ) }
by A1;
verum end;
hence
not Maps V is empty
; verum