 As an example, consider a model where there are two possible vases: 4 white marbles and 4 black marbles were put in both possible vases. But then another marble, called , was placed in the vase, but in one possible vase, was white, and in the other it was black. Thus in the end, there are two possible vases: one with 5 black marbles and 4 white marbles, and the other with 4 black marbles and 5 white marbles. Suppose \(P\) assigns \(1/2\) probability to the two possible vases. Then \(P(B(\mathsf{last})) = 1/2\) is true for this variable assignment, and if any other variable assignment were chosen, the formula \((\exists x) P(B(x)) = 1/2\) would still be true.