  We argue using simple models that all successful practical uses of
probabilities originate in quantum fluctuations in the microscopic physical
world around us, often propagated to macroscopic scales. Thus we claim there is
no physically verified fully classical theory of probability. We comment on the
general implications of this view, and specifically question the application of
classical probability theory to cosmology in cases where key questions are
known to have no quantum answer. We argue that the ideas developed here may
offer a way out of the notorious measure problems of eternal inflation.

General Relativity and Quantum Cosmology;Cosmology and Nongalactic Astrophysics;High Energy Physics - Theory;Quantum Physics