From Eco’s The Infinity of Lists, a book whose recommendation I poached several months ago from Facebook:

But, from its discovery onwards, eighty years passed before the platypus was defined as a monotreme mammal; in the course of that time it had to be decided how and where to classify it, and until that moment it remained, rather disturbingly, something the size of a mole, with little eyes, front paws with four claws of the kind paws, with a tail, a duck’s bill, paws that it used to swim and to dig its burrow, the capacity to produce eggs and that of feeding its young with milk from its mammary glands.

This is exactly what a non-scientist would say about the animal upon observing it. And it’s worth noting that through this (incomplete) description by list of properties, a person would still be able to tell a platypus from an ox, whereas saying that it is a monotreme mammal would enable to one to recognize it should he come across one. (218)

I say “platypus” far too often to mean something is unfit for well-established schema. The platypus identification crisis Eco explains in this selection is not unlike what happens when, whether or not we have arrived yet at the name “amoeba,” Elkins’ scientist puzzles over how to decide upon words for such unexpected visual patterns. Yet a technical-symbolic complex presses ahead, producing totalizing references, such as “monotreme mammal,” that concentrate, reduce, and mystify a glut of describable features. The move to summary-phrase is efficient in the sense that it reduces word counts and also shrinks audience. This is another way of saying it promotes specialization.

Eco visits upon summaries and lists (thick with tropes in the example above…mole-like, duck’s bill) a historical tension:

On the one hand, it seems that in the Baroque period people strove to find definitions by essence that were less rigid than those of medieval logic, but on the other hand the taste for the marvellous led to the transformation of every taxonomy into lists, every tree into a labyrinth. In reality, however, lists were already being used during the Renaissance to strike the first blows at the world order sanctioned by the great medieval summae. (245)

Summae, not quite in the same sense as “summary,” but not far off, either, in its interest in total coverage. Lists, though, are a different vehicle altogether. What summaries seek to contain, lists allow to breathe, to roam. Now, I’m not ready to say these conditions generalize to all summaries or all lists, but the contain-roam distinction–and much of Eco’s “illustrated essay” for that matter, is useful for thinking about what these abstract forms do differently, etc., and how they complement each other.