reconsider A = {} as Subset of R by XBOOLE_1:2;
take A ; :: thesis: A is stable
let x, y be Element of R; :: according to DILWORTH:def 2 :: thesis: ( x in A & y in A & x <> y implies ( not x <= y & not y <= x ) )
thus ( x in A & y in A & x <> y implies ( not x <= y & not y <= x ) ) ; :: thesis: verum