  It is shown how all the major conceptual difficulties of standard (textbook)
quantum mechanics, including the two measurement problems and the (supposed)
nonlocality that conflicts with special relativity, are resolved in the
consistent or decoherent histories interpretation of quantum mechanics by using
a modified form of quantum logic to discuss quantum properties (subspaces of
the quantum Hilbert space), and treating quantum time development as a
stochastic process. The histories approach in turn gives rise to some
conceptual difficulties, in particular the correct choice of a framework
(probabilistic sample space) or family of histories, and these are discussed.
The central issue is that the principle of unicity, the idea that there is a
unique single true description of the world, is incompatible with our current
understanding of quantum mechanics.
