the question ‘why is there a system?’ can only be answered by saying that the system exists because it is made. ... And this latter ... implies ... that the activity by which the language is made is itself systematic. ... the development of a language is not a constant “changing” ..., but a constant systematization. And every “language stage” represents a systematic structure exactly because it is a moment of the systematization.
(Coseriu 1958; 271f)