  Since Quine (1960), it is generally accepted that mass nouns refer cumulatively. Consider a mass noun M. Suppose that we can truly say of something x that This is M (with this referring to x) and of something distinct, y, that This is M (with this now referring to y). Then in the same circumstance, we can also refer to x and y together, and say of x and y that This is M. This property of mass nouns is called cumulative reference.  Plural count nouns also have the same property. Let Ns be a plural count noun. If these are Ns and those are Ns, then we can refer to these and those together, and say of all of them that they are Ns.