  We analyze the notion that physical theories are quantitative and testable by
observations in experiments. This leads us to propose a new, Bayesian,
interpretation of probabilities in physics that unifies their current use in
classical physical theories, experimental physics and quantum mechanics.
Probabilities are the result of quantifying the domain of possibilities that
results when we interpret observations within the framework of a physical
theory. They could also be said to be measures of information used to make
predictions based upon a physical theory.
