the probability of a physical system in a particular state, then the above theorem enunciates that
where
signifies a universal function of the argument
. Now, however
may be defined we can certainly infer from the Calculus of Probabilities that the probability of a system, composed of two entirely independent systems, is equal to the product of the separate probabilities of the individual systems. For example, if we take for the first system any terrestrial body whatever and for the second system any hollow space on Sirius, which is traversed by radiations, then the probability