It is perhaps worth explaining why there is a special importance in the present development of the theory of the State. Law, like every social phenomenon, is subject to perpetual change; indeed any scientific study of law must necessarily involve an analysis of the evolution of legal institutions. In a sense, therefore, the trasnformation of the state is also the transformation of its law.

But we must go a little deeper. The real justification of this book is the immediate situation of political theory. Just as every living being has moments in its existence when, even while obeying the general law of its life, it undergoes a change that is especially fundamental in importance, so it is in the history of peoples.