This is only 10 pages. Written by an air force colonel - PhD -
   on the dangers of metaphors.

   That's where we take the logic from one sphere of knowledge and
   apply it to another sphere of knowledge to generate a conclusion
   in the minds of the audience.

   it's used for good, but it is also misused. and if you don't
   feel like reading it, this graphic I snipped form it sums up on
   the problem.. *especially* of "what if* stuff but of
   metaphors/analogies in general.