A misunderstanding about the notion of system has undermined discussions on complexity in social sciences. Social systems are fundamentally actors systems, whereby the arrangement of intentionalities can be used as a leading thread for the understanding of these systems’ rationales. The situation is obviously different in natural sciences. In this context, complexity can be defined in physics and mathematics by higher level of unpredictability level, which is not the case in social worlds. Hypercom-plexity is based on massive interactions between actors, objects, and environments and this interactivity is all the more intelligible when actors’ expectations, desires, fears, and projects are known. As a result, future can be addressed as a more accessible as well as a more essential object for social sciences. The examples of “demographic transition” and of individual residential choices clearly illustrate this proposition.