Learning that arbitrariness from Saussure means there is no logical connection between the sound of morpheme and its meaning. But can we brain storm about this topic a little bit?
When it comes to the word "change", I'd rather put it in a larger way which is "development". I want to show an example: If you learn Chinese, then you would know actually mandarin is the one of "Chinese". If you go to the east and south of China, you would find, the so-called Chinese can't help you at all. Especially the sounds part, they are all different. The reason of this phenomenon is in ancient time, people of north of China moved to the different places, and settled down. The same (at vocal, shape, meaning) language changed through time.
In this case, the same original language contains dialects. These different dialects develop in their own ways among different social groups. Then why can't I agree the opinion as title saying? Language change is arbitrary. Hypothesis of mine: Language change is not absolute rule-governed. In some ways, it is arbitrary too.
Do studies suggest that language change is arbitrary, or are their rules or at the least generalisations that can be made?