 Perhaps there are further metaphysical desiderata that we might impose on the interpretations. For example, there appear to be connections between probability and modality. Events with positive probability can happen, even if they don’t. Some authors also insist on the converse condition that only events with positive probability can happen, although this is more controversial — see our discussion of ‘regularity’ in Section 3.3.4. (Indeed, in uncountable probability spaces this condition will require the employment of infinitesimals, and will thus take us beyond the standard Kolmogorov theory — ‘standard’ both in the sense of being the orthodoxy, and in its employment of standard, as opposed to ‘non-standard’ real numbers. See Skyrms 1980.) In any case, our list is already long enough to help in our assessment of the leading interpretations on the market.