  It is shown that quantum mechanics is, like thermodynamics, a
phenomenological theory i.e., not a causal theory, ( not because it is a
statistical theory - statistical theories with caused probability distributions
can be regarded as causal) but because pure states, i.e., probability
distributions of measurement values, cannot inhere in elementary particles and
therefore cannot change when their world tubes intersect and hence they cannot
be regarded as interacting causally. By a causal theory is meant a theory that
specifies the changes in time of the states of causally interacting entities in
its domain. The areas in quantum mechanics in which causal interactions are
relevant include, though not explicitly, measurement and therefore the Born
rule, and, explicitly, the unitary Schrodinger time development of states. The
Born rule probabilities are shown to to refer not to conjoint superpositions of
eigenstates but to classical mixtures of mutually exclusive eigenvalues and the
Schrodinger time development of states is shown to refer to the time
development of the states of non-causally interacting elementary particles and
hence cannot be regarded as as a causal time development equation, appearances
to the contrary notwithstanding. The recognition that quantum mechanics is not
a causal theory but a phenomenological theory like thermodynamics does not
affect the way it is employed to calculate an predict and hence preserves its
empirical success but it does allow a typically simple phenomenological theory
explanation of entanglement and other apparently non-local phenomena.
