Theories and empirical researches: towards a common framework

Some examples of relationships between empirical and theoretical researches are introduced. A new theoretical framework, which is based on the notion of second order variables and on that of space of action, production and communication (APC), is defined. This allows a unifying approach to some didactical phenomena. The APC space is framed within the existing literature and illustrated through a concrete example. The theoretical framework is then compared with the anthropological approach of Y. Chevallard and used to discuss the notion of ostensive/non ostensive objects.