  The measurement problem is to explain why a system which is in a linear
combination of states appears, upon measurement, to be in just one of those
states. The solution given here is to first show that if one assumes linear,
unitary, no collapse, no particle quantum mechanics, the different versions of
reality are completely isolated from each other. This then implies only the
eigenstates appropriate to the measurement setup will be perceived. In a
Stern-Gerlach experiment, for example, only spin up or spin down will be
perceived, but never a combination of the two.
