let U1, U2 be Universe; :: thesis: ( U1 c= U2 or U2 in U1 )
( ( On U1 c= On U2 or On U2 in On U1 ) & U1 = Rank (On U1) & U2 = Rank (On U2) ) by Th54, ORDINAL1:26;
hence ( U1 c= U2 or U2 in U1 ) by CLASSES1:42, CLASSES1:43; :: thesis: verum