 CP and CPI are used to argue that it is not possible that the course of nature should change as Hume supposes  [6]  The argument assumes that natural kinds of objects are defined and individuated by all the qualities that belong to the same mass, or same cause. Shepherd rebuts Hume’s contrary claim by refuting his examples. She allows the possibility that stuff that tastes like salt and has sensible qualities otherwise like those of snow might fall from the clouds, but CPI requires that the difference between them has a cause. Each is an efficacious compound different in kind from the other, and only one is properly called “snow” (ERCE: 69). Again, Hume supposes nature might alter the “secret causes” while keeping the sensible qualities the same, but this is impossible according to CPI. In general, no matter how unexpected the qualities collected in an object may be in the future, it cannot alter the way qualities are determined to exist. 