Whatever indeterministic airs these interpretations may give themselves, they all involve the metaphysical idea that not only can we deduce and test predictions, but that, in addition, nature is more or less 'determined' (or 'undetermined'); so that the success (or failure) of predictions is to be explained not by the laws from which they are deduced, but over and above this by the fact that At present I think that the question of the relation between the various interpretations of probability theory can be tackled in a much simpler way by giving a formal system of axioms or postulates and proving that it is satisfied by the various interpretations.