  In 1926, Dirac stated that quantum mechanics can be obtained from classical
theory through a change in the only rule. In his view, classical mechanics is
formulated through commutative quantities (c-numbers) while quantum mechanics
requires noncommutative one (q-numbers). The rest of theory can be unchanged.
In this paper we critically review Dirac's proposition.
  We provide a natural formulation of classical mechanics through
noncommutative quantities with a non-zero Planck constant. This is done with
the help of the nilpotent unit, which squares to zero. Thus, the crucial r\^ole
in quantum theory shall be attributed to the usage of complex numbers.
  The paper provides English and Russian versions.
