  The Hamilton-Jacobi method is generalized, both, in classical and
relativistic mechanics. The implications in quantum mechanics are considered in
the case of Klein-Gordon equation. We find that the wave functions of
Klein-Gordon theory can be considered as describing the motion of an ensemble
of particles that move under the action of the electromagnetic field alone,
without quantum potentials, hidden uninterpreted variables, or zero point
fields. The number of particles is not locally conserved.
