   There are, then, for the combinatorialist no intrinsically modal  phenomena; there are just all of the various worlds that exist on  unrestricted combinatorial grounds alone. Ultimately, all genuine  possibilities, simple or not, are just states of affairs that exist  in these combinatorial worlds in the sense of AE3. However, it is not immediately as clear how to understand many intuitive  necessities/impossibilities involving complex  structural universals, for example, the impossibilities noted in the  previous section, viz., that something simultaneously have a mass of  both 1kg and 2kg or simultaneously be both a baboon and a hoolock.  Likewise, it is not entirely clear how combinatorialism accounts for  intuitive facts about essential properties, such as that our water  molecule W is essentially water or that Algol is essentially a dog. Combinatorialists argue that such modal facts can nevertheless  be explained in terms that require no appeal to primitive modal  features of the world (Armstrong 2004b, 15). 