The perspective suggested by Anthony Giddens on the differences between modern and pre-modern societies reveals that modernity possesses a dynamic that did not exist in comparable form before the 17th century. Giddens attributes this dynamic to three main factors. The first factor is the separation of space and time. Closely related to this is the second factor: the development of social mechanisms that allow certain societal activities to be lifted from their previously location-bound "bed" of occurrence and restructured across vast spatial and temporal distances. The third factor is the reflexive appropriation of knowledge about society in the social sciences. Giddens illustrates, with examples, the extremes to which the dynamics of modernity can lead.