The Pre-Existing Linguistic Community

In order to exist, there must be a pre-existing linguistic community. Including that if you're a brain in a vat. Victor and Shine has this thing called a private language argument. If you were the only person on planet earth with no communication with anybody else, you couldn't invent a language. There can't be a language that only exists within one person for one person. That can't just poof appear all of a sudden.