A third way of arguing for rule-consequentialism is contractualist (Harsanyi 1953, 1955, 1982, 1993; Brandt 1979, 1988, 1996; Scanlon 1982, 1998; Parfit 2011; Levy 2013). Suppose we can specify reasonable conditions under which everyone would choose, or at least would have sufficient reason to choose, the same code of rules. Intuitively, such an idealized agreement would legitimate that code of rules. Now if those rules are the ones whose internalisation would maximise the expected good, contractualism is leading us to rule-consequentialism’s rules.