  In a quantum theory of gravity spacetime behaves classically when quantum
probabilities are high for histories of geometry and field that are correlated
in time by the Einstein equation. Probabilities follow from the quantum state.
This quantum perspective on classicality has important implications: (a)
Classical histories are generally available only in limited patches of the
configuration space on which the state lives. (b) In a given patch states
generally predict relative probabilities for an ensemble of possible classical
histories. (c) In between patches classical predictability breaks down and is
replaced by quantum evolution connecting classical histories in different
patches. (d) Classical predictability can break down on scales well below the
Planck scale, and with no breakdown in the classical equations of motion. We
support and illustrate (a)-(d) by calculating the quantum transition across the
de Sitter like throat connecting asymptotically classical, inflating histories
in the no-boundary quantum state. This supplies probabilities for how a
classical history on one side transitions and branches into a range of
classical histories on the opposite side. We also comment on the implications
of (a)-(d) for the dynamics of black holes and eternal inflation.
