 | at least) arbitrarily precisely.  In the latter, this is meaningless.  The boundary between
    | the two is arbitrary to a very large extent.  ...  -- but this does not change the fact
    | that in each method of description the boundary must be placed somewhere, if the method
    | is not to proceed vacuously, i.e., if a comparison with experiment is to be possible.
    |
    | John von Neumann,
    |'Mathematical Foundations of Quantum Mechanics',
    | Translated from the German edition by Robert T.