  Quantum mechanics is nonlocal. Classical mechanics is local. Consequently
classical mechanics can not explain all quantum phenomena. Conversely, it is
cumbersome to use quantum mechanics to describe classical phenomena. Not only
are the computations more complex, but - and this is the main point - it is
conceptually more difficult: one has to argue that nonlocality, entanglement
and the principle of superposition can be set aside when crossing the "quantum
$\rightarrow$ classical" border. Clearly, nonlocality, entanglement and the
principle of superposition should become irrelevant in the classical limit. But
why should one argue? Shouldn't it just come out of the equations? Does it come
out of the equations? This contribution is about the last question. And the
answer is: "it depends on which equation".
