  The central idea advocated in this paper is that {forming the black hole
horizon is attended with transition from the classical regime of evolution to
the quantum one}. We justify the following criterion for discriminating between
the classical and the quantum: {spontaneous creations and annihilations of
particle-antiparticle pairs are impossible in the classical world but possible
in the quantum world}. We show that it is sufficient to {change the overall
sign of the spacetime signature in the classical picture of field propagation
for it to be treated as its associated quantum picture}. To describe a
self-gravitating object at the last stage of its classical evolution, we
propose to use the Foldy--Wouthuysen representation of the Dirac equation in
curved spacetimes, and the Gozzi classical path integral. In both approaches,
maintaining the dynamics in the classical regime is controlled by
supersymmetry.
