The axiom $\left(\neg \neg \phi \to \phi \right)\to \left(\phi \vee \neg \phi \right)$, where $\neg$ is a unary negation and $\vee$ and $\to$ are disjunction and conditional connectives, respectively. In the context of intuitionistic logic, to include the stability principle as a new axiom corresponds to the thesis that every stable formula is decidable (in the intuitionistic sense).