All arrays can be adjustable?

[David C. Plummer <DCP@QUABBIN.SCRC.Symbolics.COM>]

Maybe if we could figure out how to express the various types of arrays
using set language we wouldn't accidentally invert phrases.  For
example, I think everybody agrees that simple is a subset of
  (intersect not-adjustable not-fill-pointer not-displaced)
That's the >only< thing that phrase says.  It can't be inverted,
conversed, contra-positived, or anything to say that simple arrays are
not adjustable.  The contra-positive (the only thing provably true) is
that the UNION of adjustable, fill-pointered or displaced arrays is a
subset of non-simple arrays.