We have attempted to limit this study, originally intended for oral présentation, both in form and in scope, while trying to give serious consideration to some recent theoretical contributions regarding a vast and delicate empirical topic in a field where conceptual innovations are all too rare. Our purpose is to examine the entailments of studying Algerian literature, or rather literatures, as a system and, at the same time, as a sub-system, i.e. as a structural whole in which different genres are, to a limited extent, interrelated as well as as a sub-structure of a complex social discourse in which orality and scripturality confront each other. Simultaneously, we endeavour to underline the fact that great caution must be deployed the moment one attempts to use tales, myths or poetry as source material on a given society : such documents are not simply "mirrors". We have thus sought to sketch out briefly some considerations on different forms of knowledge and/or expression (myth, dream or science) which are not generally thought of together, at least in the academic world.