  This is not a problem if chance too is relative to a type of trial, for we may simply make the dependence on choice of reference class explicit in both sides of RCT. If chances were relative frequencies, it would be easy enough to see why chance is relative to a type of trial. But chances aren’t frequencies, and single-case chance is almost universally taken to be not only well-defined for a specific event, but unique for that event. We naturally speak of the chance that this coin will lands heads on its next toss, with the chance taken to be a property of the possible outcome directly, and not mediated by some particular description of that outcome as an instance of this or that kind of trial. Moreover, for chance to play its role in the  Principal Principle  (§1  and Supplement  A.1),  there must be a unique chance for a given event that is to guide our rational credence, as we have only one credence in a particular proposition stating the occurrence of that event. (Indeed, the inability of frequentists to single out a unique reference class, the frequency in which is the chance, was taken to be a decisive objection to frequentism.) On the standard understanding of chance, then, there is a mismatch between the left and right sides of the RCT. And this gives rise to a counterexample to RCT, if we take an event with a unique non-trivial single-case chance, but such that at least one way of classifying the trial which produced it is such that the sequence of outcomes of all trials of that kind is not random. The trivial case might be this: a coin is tossed and lands heads. That event happened by chance, yet it is of the type ‘coin toss which lands heads’, and the sequence consisting of all outcomes of that type is not random.