> I agree: there are no rules in a language.

Really? Isn't that a bit broad? It may be half true for some languages but definitely not for all.

For example in Germany we have the "Der Duden" which is not only a dictionary that defines the correct spelling of words but also contains a huge set of grammatical rules. It's still the de-facto standard for correct language in German.

And even in english you'd probably agree that there are some rules, e.g. when it comes to the correct spelling of words.