This chapter addresses the problem of whether classical logic can be used as a universal system of logic and whether it can be applied, profitably and sensibly, in all areas where logic needs to be applied. More specifically, we focus on modal and temporal logics and ask whether the use of such special logics, as compared with the use of classical logic, is advantageous. We examine what we lose and what we gain if we use classical logic instead of specialized logics to describe and reason about the same (e.g. temporal) phenomena.