 This principle holds regardless of which interpretation of “sortal” you take. Not only is “is not a cat” not a substantive sortal (Wiggins), you cannot count the non-cats since they include dogs, table, molecules, et cetera. However, for two of the other logical operators, disjunction and conjunction, the situation seems more complex. The expressions “dog or cat”, “apple or orange” and “fork or spoon” all seem to be well-behaved with respect to counting and identifying; we can easily imagine a city ordinance forbidding homeowners to have more than four dogs or cats. On the other hand, “dog or natural number” and “cat or clock” seem to provide methods of counting but seem unnatural as sortals.