 The answer seems to be 0. To see why, note that all those propositions \(A_n\) should be assigned equal credences \(c\), by the fairness of the lottery. Then it is not hard to show that, in order to satisfy Probabilism, a positive \(c\) is too high and a negative \(c\) is too  low.[4]  So, by Probabilism, the only alternative is \(c = 0\). But this result violates Countable Additivity: by the fairness of the lottery, the left side is