  According to the holographic principle, the information content assigned to a
gravitational region is processed by its lower dimensional boundary. As an
example setup compatible with this principle, the AdS/CFT correspondence relies
on the existence of D-branes in superstring theory. Black hole complementarity
is inevitably linked to holography and states that information associated with
the collapsed pure state is reflected in the near horizon region. Yet, if this
is so, it is indispensable to understand the mechanism that makes black holes
viewed from the outside evolve unitarily. We here argue that the information
preserving quantum atmosphere of the black hole emerges from hidden variables
on its horizon which would necessitate going beyond a probabilistic description
within standard quantum theory. In AdS/CFT, this would mean that the completion
of the semiclassical subalgebra to the complete boundary algebra has to be
traced back to the emergent near horizon Hilbert space structure. The present
investigations suggest that spacetime horizons, in general, may play a crucial
role in restoring a long speculated ontology in quantum mechanics.
