Philosophy traditionally deals with such lexicalized concepts as WISDOM, VIRTUE, REASON, WORLD VIEW, INFINITE UNIVERSE, and PHILOSOPHY. They trigger interest in philosophy particularly because they are hard to understand and explain. It is all the more surprising that many contemporary philosophers focus on such concepts as DOG, CHAIR, and FLIGHT to build their theories and provide examples. The article argues that to preserve topical equilibrium and avoid methodological problems, both classes of concepts should be involved in philosophical theorization and exemplification. The first part critically discusses attempts at identifying these classes as ordinary vs. big (Gauker), empirical vs. pure (Kant), and concrete vs. abstract (contemporary psycholinguistics). It introduces the opposite pair simple empirical vs. complex demanding concepts as an alternative heuristic tool to evaluate concepts. The second part elaborates on the concept of concept and structural similarities between the two classes of concepts in semantic and 'onomantic' perspectives. The third part shows that despite structural similarities, such factors as the availability of empirical data, identification of the referent, historical and theoretical loadedness, complexity, and demandingness indicate that simple empirical and complex demanding concepts should be addressed in different ways. The final part elaborates on the notion of topical equilibrium as a philosophical method and norm and discusses two further examples (COW and ARTHRITIS) from contemporary debates in conceptual engineering.