  A distinction is made between two kinds of consistent histories: (1) robust
histories consistent by virtue of decoherence, and (2) verifiable histories
consistent through the existence of accessible records. It is events in
verifiable histories which describe amplified quantum fluctuations. If the
consistent-histories formalism is to improve on the Copenhagen interpretation
by providing a self-contained quantum representation of the quasi-classical
world, the appropriate quantum state must track closely all macroscopic
phenomena, and the von Neumann entropy of that quantum state ought to change in
the same direction as the statistical entropy of the macro-world. Since the von
Neumann entropy tends to decrease under successive branchings, the evolution of
an entropy-increasing quasi-classical world is not described by the process of
branchings only: mergings of previously separate histories must also occur. As
a consequence, the number of possible quasi-classical worlds does not have to
grow indefinitely as in the many-world picture.
