 James Delgrande (1987) proposed the system NP as a different extension of CK. The main difference is that B satisfies Cautious Monotonicity, whereas NP satisfies Rational Monotonicity. In Delgrande’s interpretation, an instance of Rational Monotonicity is the inference from the premises “ravens normally fly” and “it is not the case that normally ravens are not black” to “black ravens normally fly”. Note that Cautious Monotonicity predicts the inference from “ravens normally fly” and “ravens normally are black” to “black ravens normally fly”. The existence of systems B and NP makes clear that strictly speaking, RMon and CMon are logically independent. But it is fair to say that RMon is essentially stronger than CMon, because in most environments one can infer \(\neg(A&gt;\neg C)\) from \(A&gt;C\). In the ordering semantics, RMon needs weak orders which satisfy Modularity (for all worlds \(t, u, v, w \in W\), if \(t\prec_w u\), then \(t\prec_w v\) or \(v\prec_w u\)), while CMon needs only transitive relations. But RMon may be satisfied without CMon being satisfied if one has a weak order over an infinite set without anything like the limit assumption and uses a selection function or a minimal models approach. This is the case in Delgrande  (1987).[2]