  We show that the quantum wavefunction, interpreted as the probability density
of finding a single non-localized quantum particle, which evolves according to
classical laws of motion, is an intermediate description of a material quantum
particle between the quantum and classical realms. Accordingly, classical and
quantum mechanics should not be treated separately, a unified description in
terms of the Wigner distribution function being possible. Although defined on
classical phase space coordinates, the Wigner distribution function
accommodates the nonlocalization property of quantum systems, and leads to both
the Schrodinger equation for the quantum wavefunction and to the definition of
position and momentum operators.
