Private language—what we say to ourselves, how we cogitate while alone—is greatly dependent on public language, that which is readily understood by many.
In fact, private language is so dependent on public language, it can be argued that a private language completely divorced from public language cannot exist.
It is obvious that anyone wanting to influence or control large numbers of people will address them in public language.
It is less obvious, that those same people frequently will also seek to change the public language itself.
Sometimes this language changing is a good thing as that is how civilizations adapt and grow. It is probably best, or usually best, when civilizational changes arise organically from the whole society or from important parts of society that are behaving honestly.
Sometimes, however, the changing of public language is done dishonestly by small numbers of people who have seized positions of power, sometimes precisely for that purpose.
They change public language to further their positions, ideas, or programs; to seize control of public topics; to seize or secure power over the public.
It is not as easy to parse this as it may seem. Who is restricting honest organic input into public language? Or when is organic input into public language itself but a ruse to falsely commandeer that language?
After Lenin and Stalin seized control of the public languages of the Soviet Union, we can see a clear-cut example of bad actors creating a basis for indoctrination. Before they seized power, we can see an example of a dishonest “organic” group seeking to commandeer control of public language.
And how do we see that today, through the lens of “history”?
Firstly, whose history? The same problem with public language arises.
Secondly, maybe we can never know. Maybe only societal laws or rules of governance can help us determine what’s right or best. But then the same problem arises.
Whose laws, whose rules?
In this sense both public and private languages have enormous problems basing themselves on anything.