take F = uparrow (Top L); :: thesis: F is proper
assume not F is proper ; :: thesis: contradiction
then A1: F = the carrier of L by SUBSET_1:def 6;

now

let x, y be Element of L; :: thesis: x = y
A2: F = {(Top L)} by WAYBEL_4:24;
then x = Top L by A1, TARSKI:def 1;
hence x = y by A1, A2, TARSKI:def 1; :: thesis: verum

end;

hence contradiction by STRUCT_0:def 10; :: thesis: verum