  Einstein initially objected to the probabilistic aspect of quantum mechanics
- the idea that God is playing at dice. Later he changed his ground, and
focussed instead on the point that the Copenhagen Interpretation leads to what
Einstein saw as the abandonment of physical realism. We argue here that
Einstein's initial intuition was perfectly sound, and that it is precisely the
fact that quantum mechanics is a fundamentally probabilistic theory which is at
the root of all the controversies regarding its interpretation. Probability is
an intrinsically logical concept. This means that the quantum state has an
essentially logical significance. It is extremely difficult to reconcile that
fact with Einstein's belief, that it is the task of physics to give us a vision
of the world apprehended sub specie aeternitatis. Quantum mechanics thus
presents us with a simple choice: either to follow Einstein in looking for a
theory which is not probabilistic at the fundamental level, or else to accept
that physics does not in fact put us in the position of God looking down on
things from above. There is a widespread fear that the latter alternative must
inevitably lead to a greatly impoverished, positivistic view of physical
theory. It appears to us, however, that the truth is just the opposite. The
Einsteinian vision is much less attractive than it seems at first sight. In
particular, it is closely connected with philosophical reductionism.
