 A possible solution to the problem of combining heterogeneous logics, which naturally leads us to the deeper question of “what is a logic?”, is to consider a common component of the majority of logics (but still excluding certain substructural logics): their respective consequence relations. Thus, given \({{\cal L}}_1\) and \({{\cal L}}_2\) presented in different ways, it is always possible to extract the respective consequence relations and then combine them (taking, for instance, their supremum in an appropriate lattice of consequence relations). But in this way, the resulting logic \({{\cal L}}\) is presented in a very abstract way: the only information available from \({{\cal L}}\) is its consequence relation, and so the characteristics and particularities of each logic component are definitively lost.