In a contest between belief and non-belief, the burden of proof is on belief.
why would there even be a contest between belief and non-belief? belief isn't science, why would you want to use science to prove or disprove a thing that's not science? i remembered reading something that stated "you should believe in god." the logic is, if god doesn't exist, then you have nothing to lose. but if he/she/it exists and you don't, then you are screw.
so if you don't want to use the word "ki", and say you have to teach the native, how would you explain some of the stuffs that part of the language. i mentioned that "khi" in my language is the same as "ki" or "chi". khi hau = weather (the states of the air outside). if i don't use khi, then the word "hau" meant your rear-end. kinda hard to talk about your rear-end.