let A be Ordinal; :: thesis: ( not A c= 1 or A = {} or A = 1 )
assume that
A1: A c= 1 and
A2: A <> {} and
A3: A <> 1 ; :: thesis: contradiction
A c< 1 by A1, A3;
hence contradiction by A2, Th14, ORDINAL1:11; :: thesis: verum