 First, let’s note why it is important to make this assumption. Would it not be sufficient to say merely that one of the sources of disutility for a credence is its inaccuracy, and then to point out that any credence function that isn’t a probability function is accuracy dominated? If it could always be guaranteed that, for any non-probabilistic credence function, none of its accuracy dominators has any epistemic vice to a greater degree than does the credence function it dominates, then this would be sufficient. But, if it were possible that every accuracy dominator is guaranteed to be better along the dimension of inaccuracy but worse along some other dimension of epistemic disutility, then being accuracy dominated would not rule out a credence function as irrational. Thus, if the accuracy dominance argument for Probabilism is to work, we must claim, with  Credal Veritism,  that inaccuracy is the only source of epistemic disutility for credences.