you are allowed to assign probabilities to non-repeatable events, i.e. what's the probability there is life on mars I get the impression that believers in the

you are allowed to assign probabilities to non-repeatable events, i.e. what's the probability there is life on mars I get the impression that believers in the Bayesian Revolution often also subscribe to the many worlds quantum interpretation, which would make P(life on Mars) a repeatable event.