Those abstract things are then said to be "multiply instantiated", in the sense of "picture 1", "picture 2", etc., shown below. It is not sufficient, however, to define "abstract" ideas as those that can be instantiated and to define "abstraction" as the movement in the opposite direction to instantiation. Doing so would make the concepts "cat" and "telephone" abstract ideas since despite their varying appearances, a particular cat or a particular telephone is an instance of the concept "cat" or the concept "telephone". Although the concepts "cat" and "telephone" are "abstractions", they are not "abstract" in the sense of the objects in "graph 1" below. We might look at other graphs, in a progression from "cat" to "mammal" to "animal", and see that "animal" is more abstract than "mammal"; but on the other hand "mammal" is a harder idea to express, certainly in relation to "marsupial" or "monotreme".