It's been about 30 years since I read Aristotle. At the time, I remember him as a nit-picker and concept-slicer whose way was determined by the problems his predecessors had run into. I admired him for undoing some of the weirdisms of Plato and returning thought to a path that accorded better with the basics of our experience, but, overall, he was a hurdle to be gotten over on the way to other projects.
I've been re-reading Aristotle recently because I want to know how we came to see knowledge as shaped like a tree, and Aristotle is the guy who first articulated that. So, I've been reading his Metaphysics and then will work backward to his Categories. The Metaphysics, usually considered one of his drier works, reads to me the way Bach sounds: Every note unpredictably perfect, finding the beauty in order and in its occasional transgression. And with Aristotle we have the thrill of watching someone get to define the most basic of concepts: What does "unity" mean? What does "quality" mean? He's not inventing these terms; he's "merely" defining them and systematizing them so thought can come out of its everyday-ness and achieve its initial clarity.
In the Metaphysics, Aristotle wants to know what it means for something to be. Oh yeah, just a simple little question. In the Categories, he's come up with the 10 basic ways of asking about a thing: What's it made of, what's it for, etc. So, if those are the 10 parameters, which of them really makes something into an existing thing? That is, now we know what makes a table into a table, but what do we say about what lets it be a thing at all?
Aristotle's answer is that those aren't separate questions. If you're going to exist, you have to exist as something--a table, a human, a piping hot souvlaki. That turns philosophy back from a bad course that it had embarked on, and to which it would return as the influence of Aristotle wore off after the Middle Ages: Thinking of the meaning of things (the table as a table) as separable from their existence (the table as a thing). That path leads to the trivialization of meaning. But not for Aristotle. For him, if you want to know what makes Socrates real, you have to see how Socrates is a human ... which means understanding him within a category (animals) with differentiated sub-categories (the animals that are rational). Thus, taxonomy and existence are fused: To be is to be in a taxonomy of meaning.
Indeed, you can see in Metaphysics Aristotle's struggle to unearth the difficult nature of nested categories, which we all take for granted. "Animals" contains humans and giraffes, but we're not led to think that there is an eternal Giant Animal apart from the humans, giraffes, etc. Plato did make that mistake; he thought "animal-ness" existed as an eternal essence apart from all individual animals. Aristotle criticizes Plato because there's no good way to explain how animal-ness and particular animals unite. With nested containers, they are never really separate. By my skewed reading, that's the notion Aristotle is heading toward.
Aristotle is trying to hold existence and meaning together: to be means to be a this-thing or that-thing. We moderns want to object. We assume that first the world exists and then we divide it into categories. Further, we think that the particularities of the taxonomy depend on accidents of culture and history. So, here's a question that arises from reading Metaphysics: Is it possible that we and Aristotle simply understand differently what it means to live in a world?
After all, the music of Aristotle's thought comes from his assumption that the principles of knowledge are the same as the principles of the universe. The categories are not "mere" categories of thought for him. They are also the way the cosmos is arranged. If the order of knowledge and the order of the world are not the same, reasoned Aristotle, then knowledge isn't possible. Knowledge is only possible if the universe is ordered in knowable ways.
Now, we live in a world that's somewhat more diverse than Aristotle's, and we no longer assume that there is a single order of the universe. We certainly discover that when we start to build taxonomies of our own corporate knowledge or when we think we'll just hook up all the taxonomies and have ourselves a Semantic Web. Taxonomies nowadays are built to reflect how users search, not some abstract ideal of how the universe is. In fact, we're building metadata-rich collections so every user can create her own taxonomy on the fly. And yet ...
... Aristotle's sense of the world strikes me as more accurate than the one that typically undergirds our modern outlook. We think there's a real world that our taxonomies lie on top of. Aristotle—if he could understand the modern distinction we're drawing—would tell us that a world apart from the categories of understanding would be by definition unknowable. Knowledge is the way the world shows itself to us in all its beauty and order.
David Weinberger edits "The Journal of the Hyperlinked Organization", e-mail email@example.com.