Here is a fascinating interview with a fascinating woman, Alexandra Aikhenvald, talking about a fascinating subject; one which is overdue for attention on this here blog: rare languages.
Imagine how different politics would be if debates were conducted in Tariana, an Amazonian language in which it is a grammatical error to report something without saying how you found it out - as Alexandra Aikhenvald tells us its speakers tell her. ... Once I asked, "Can I use this word this way?" and the response was, "Of course, you're foreign, you can say a wrong thing. But I can't say that."
... English I can tell my son: "Today I talked to Adrian", and he won't ask: "How do you know you talked to Adrian?" But in some languages, including Tariana, you always have to put a little suffix onto your verb saying how you know something - we call it "evidentiality". I would have to say: "I talked to Adrian, non-visual," if we had talked on the phone. And if my son told someone else, he would say: "She talked to Adrian, visual, reported." In that language, if you don't say how you know things, they think you are a liar.
This is a very nice and useful tool. Imagine if, in the argument about weapons of mass destruction, people had had to say how they knew about whatever they said. That would have saved us quite a lot of breath.
