David Weinberger further ponders on the Third Age of Order:

First Order: You arrange physical objects: You shelve books, you file papers, you put away your silverware.

Second Order: You arrange separate, smaller objects that contain metadata about the first order objects: You create a card catalog. You make entries in a ledger. You index a book. You now have a second organizational scheme (e.g., the books are shelved by subject but the cards are arranged alphabetically), and it's physically easier to navigate

Third Order: You create electronic metadata so you can organize it in ways that simply weren't feasible before.

And, within the Third Age, on the nature of data and metadata:

So, in the Third Age of Order, all data is metadata. Contents are labels. Data is all surface and no insides. It's all handles and no suitcase. It's a folder whose content is just another label. It's all sticker and no bumper.

Why does this matter? It changes the primary job of information architects. It makes stores of information more useful to users. It enables research that otherwise would be difficult, thus making our culture smarter overall. But, most interestingly (at least to me), this does the ol' Einsteinian reverse flip to Aristotle. Aristotle assumed that of the 10 categories by which one could understand a thing, one must be primary: Where that thing fits into the tree of knowledge. So, you could say that Alcibiades is made of flesh or lived in Greece, but if you really want to understand him, you have to say that he is an animal of a particular kind. But, now that everything is metadata, no particular way of understanding something is any more inherently valuable than any other; it all depends on what you're trying to do. The old framework of knowledge — and authority — are getting a pretty good shake.