In article <kh3Ec.69461$sj4.24890@news-server.bigpond.net.au>, 
jim_breen@idontreadhotmail.com wrote:
:馬鹿の壁? (バカの壁) Can you give me a good definition? I have Googled
:and mainly found pages talking about 小泉   8-)}

This is coined by 養老孟司, an ex-professor of Tokyo Univ, Anatomy III, School of Medicine.
Now he should be a professor at Kitasato, IIRC.  The word describes the phenomena
that perfect reasonings can fail if idiots cannot understand them.  The wall
is the metaphor of the idiocy that blocks the understanding.  In other words, 
the old expression 馬鹿につける薬はない says basically the same thing.