context-free language

Ong quote:

"Writing establishes what has been called 'context-free' langauge or 'autonomous' discourse, discourse which cannot be directly questioned or contested as oral speech can be because written discourse has been detatched from its author" (77).

I find it interguing that the written word, as is Ong's contention, is absent of contestability.  A question to discusses may be why is the written uncontestable? 

I would argue that written text is completely contestable in that discourse can be directed to specific audience.  However, i do believe that written communication often falls short because it doesn't carry inflection.  It is easier to make judgements reliability and accuracy of information if it is communicated vocally or visually through action, but I think Ong descibes perfectly why directions for assembling new products are often found to be frustrating or insufficient.