 In this case, since the credence function \(c^\dag\) is not a probability function, it is accuracy dominated by Joyce’s theorem and thus it is ruled out as irrational by  Naive Dominance,  just as the option of practising is ruled out as irrational in Driving Test. However, this is a situation in which adopting an option influences the way the world is in such a way that it affects the utility of the option, just as choosing whether or not to practise does in Driving Test. If I were to have credence function \(c^\dag\), I would be more accurate than I would be were I to have any other credence function. Thus, it seems that, just as we said that practising is in fact the only option that shouldn’t be ruled irrational in Driving Test, so now we must say that credence function \(c^\dag\) is the only option that shouldn’t be ruled irrational in Thwarted Accuracy. But of course, it then follows that Probabilism is false, for there are situations such as this one in which it is irrational to do anything other than have a non-probabilistic credence function.