 Rational Monotony states that no conclusions of \(\Sigma\) are lost when adding formulas \(\phi\) to \(\Sigma\) that are not contradicted by \(\Sigma\). Rational Monotony is a more controversial property than Cautious Monotony. For instance,  Stalnaker (1994)  gave a counter-example to it (see the  supplementary document)  in view of which it is clear that not in all application contexts Rational Monotony is a desirable property of defeasible reasoning. 