 The question of substance dualism within one of the three species only arises in relation to the third species or created being. This species is itself a unity in multiplicity, since it is a single substance comprising innumerable spirit particles, which Conway also calls species (a term indicative of their being parts that constitute the whole). The third species as a whole is thus a unity of multiplicities (“the whole creation is just but one substance or entity”, exhibiting “a general unity of creatures with one another”; Principles VII.4). Each of these spirit particles consists of infinite spirit particles, every one of which contains infinite numbers of others. These entities may be considered monadic in the sense that each is a unity. But, like created nature as a whole, they are unities in multiplicity, there being “a special and peculiar unity among the parts of one [individual] species in particular” (Principles, VII.4). It is from aggregates of these that creatures are formed. The mutability of all created beings means that there is considerable—nay infinite—variety within created nature.