Social and territorial structures form intricate relations that transcend a social stratification or spatial focus. Territorial features and geographic displacements are structuring principles for society, as societal features and social change effect the structure and use of territory. Based on our examination of the conceptual and theoretical links between spatial and social mobility, we propose a concept that represents a new form of inequality. Termed 'motility', this construct describes the potential and actual capacity of goods, information or people to be mobile both geographically and socially. Three major features of motility - access, competence and appropriation - are introduced. In this article, we focus on conceptual and theoretical contributions of motility. In addition, we suggest a number of possible empirical investigations. Motility presents us with an innovative perspective on societal changes without prematurely committing researchers to work within structuralist or postmodern perspectives. More generally, we propose to revisit the fluidification debate in the social sciences with a battery of questions that do not begin and end with whether or not society is in flux. Instead, we introduce a field of research that takes advantage of the insights from competing paradigms in order to reveal the social dynamics and consequences of displacements in geographic and social space.