The following paper is intended to discern modem elements from other elements that would not be modern anymore; whether these last ones are accurately Post Modern or not is a matter of great difficulty, and the purpose of this contribution is to merely pose the problem. In a former work we have tried to establish the keys of Modernity; our present purpose is to distinguish among certain elements which are strictly consequences of principles around which Modernity is co-jointed, and other elements that mean a certain breaking-off from such principies and, therefore, may allow us to speak about a Post Modernity.