let x be Surreal; name-r x, name-y x, name-ord x name_like x
name-ord x = dom (name-r x)
by Th105;
then A2:
name-r x, name-y x, name-ord x name_like Sum ((name-r x),(name-y x))
by Def23, Th101;
Sum ((name-r x),(name-y x)) == x
by Def23;
hence
name-r x, name-y x, name-ord x name_like x
by A2, Th103; verum