 At this point, it is convenient to notice that the question about whether or not interactive principles are generated when combining modal logics, is intrinsically related to Hume’s ‘is-ought problem’ discussed in  section 1.  Indeed, as proven in Schurz 1991, it is possible to obtain nontrivial ‘is-ought’ deductions in the combination of alethic and deontic logics provided that some bridge principles are allowed. The validity of bridge principles as \(\obcirc \varphi \rightarrow \lozenge \varphi\) is nothing else than interaction rules between connectives of the logics being combined. Such principles enjoy a similar conceptual status as the distributivity laws between conjunction and disjunction, or as the collapsing example mentioned above. Thus, in order to satisfy Hume’s thesis, a combination process generating logics without interactions should be preferred. On the other hand, a combination process allowing the creation of interactions between the connectives could grant bridge principles violating Hume’s thesis.