How is the formal calculation carried out? The answer is somewhat complicated, and there are slightly different ways of doing it, as in (Tooley 2008 and 2012b), with the method used in the latter case being perhaps slightly more perspicuous, but with both methods generating the same result. The key in both cases, moreover, is to make assumptions that increase the probability that an action that is morally wrong as judged only by its known rightmaking and wrongmaking properties is morally right relative to the totality of its morally significant properties, both known and unknown. In the absence of those ‘probability-increasing’ assumptions, it is not at all clear how the calculation could be carried out.