Premodernism: Reality is imposed from above, i.e. by the church, king, or feudal lord.
Modernism: The attempt to realize a universal shared reality based on observable phenomena. Jean-Francois Lyotard described these utopic universalized stories as "metanarratives".
Postmodernism: Reality is individually constructed and structured. Metanarratives are replaced by individual narratives and/or by narratives specific to specific sub-cultural groups.