Earlier quoted context omitted.
Why do they need to be in a language? You could represent everything as images/video sequences.
At least some has to be in a linguistic representation (check the Aydede article I linked above, it's interesting). Why? Because (i) You cannot represent everything using images, e.g. "brother", "justice", "tesseract", but more importantly (ii) it is impossible for image representations to support complex syntactic manipulations necessary for reasoning. As a very simple example, think about the syllogism that starts…
You can represent brother and justice, via imagery, but what you would be doing is using a token example, comparing and creating a type out of the two situations. Now communicating that idea without a linguistic representation would be near impossible(I can't imagine an easy way) but to apprehend it without a linguistic layer is possible. (ii) It could just be my own misunderstanding of what is being said, but does having a visual representation system, mean that symbols cannot be manipulated to interact, or does that by definition make them a language? Is this a functional definition we are working with?
As well, with words like "every" "the" "a" it sounds like these things are objects to you, and not emergent connectors inherent in a linguistic system, they exist by virtue of the language existing. A visual system may not have need for such conventions. Many of these questions or examples assume an almost external objective (at least thats my interpretation) existence of linguistics, but this is coming from a linguistic mind, and assumes the necessary existence of it.( hence my begging question comment at the beggining).
I held much the same view, until I experienced ineffable idea's and concepts in non linguistic form. Anecdotally, one can try salvia or dimethyltryptamine and gain the qualia experience of a thinking or experience without linguistics.
Good points, but I feel Impossible is too strong a conclusion based on whats been said. :)