Hans Kelsen 
Society and Nature [PDF ebook] 
A Sociological Inquiry

First published in 1998.This is Volume XIV of eighteen in the Sociology of Behaviour and Psychology series. This text is concerned with sociological inquiry into society and nature. Written in 1946, it investigates the idea that society and nature, if conceived of as two different systems of elements, are the results of two different methods of thinking and are only as such two different objects. The same elements, connected with each other according to the principle of causality, constitute nature; connected with each other according to another, namely, a normative, principle, they constitute society