Let the successor function be s(n) = the next power of 2 larger than n. So, let's check that rules 1,2,5 hold: (1) we have a first element (rule 1 is true) (2) Each of these elements has a successor element in the set (s(1)=2, s(2)=4, s(4) = 8, etc, is a long chain, but also 3 is in the set and s(3) = 4. and s(5) = 8. (5) induction holds. But rule (3) is violated since s(2) = s(3) but 2 != 3. And rule (4) is violated since 3 is not the successor of any element.