Here, the dialectical development of the Concept (which is simultaneously the progressive realisation of Reason in societies) establishes the Principle of an Age which is expressed in every area of that society. It can be likened to a simple, mono-causality. In Althusser’s the phenomena of a society are reducible to and expressive of, it’s Essence. In other words, the Essence is expressed in every area of society and is the moving Principle of Historical change.