"I think I am right in saying that the problem of intermediates is inescapably, inherently a part of all taxonomic systems other than that which springs from evolutionary biology. Speaking personally, it is a problem that gives me almost physical discomfort when I am attempting the modest filing tasks that arise in my professional life: shelving my own books, and reprints of scientific papers that colleagues (with the kindest of intentions) send me; filing administrative papers; old letters, and so on. Whatever categories one adopts for a filing system, there are always awkward items that don't fit, and the uncomfortable indecision leads me, I am sorry to say, to leave odd papers out on the table, sometimes for years at a time until it is safe to throw them away. Often on has unsatisfactory recourse to a miscellaneous category, a category which, once initiated, has a menacing tendency to grow. I sometimes wonder whether librarians, and keepers of all museums except biological museums, are particularly prone to ulcers."
- Dawins, Richard. The Blind Watchmaker. New York: Norton, 1987. p260
Recently I was re-reading The Blind Watchmaker by Richard Dawkins. It's a really great book on evolutionary biology, written for the layman. Dawkins and Stephen J. Gould are biologists whose works I really enjoy, mainly because they both have a great knack for teaching otherwise complicated subjects, especially by analogies. But there's a whole chapter in this book on taxonomy, which is basically the art of categorizing and classification. That's where I got the quotation from. I read it and thought, "This would be good for the 'stuff' blog!"
I think his point is a notable one for people trying to tame their volume of stuff. When trying to get organized, it seems that some kind of filing system or other means of categorization is inevitably going to be needed. Though as Dawkins points out, one of the side effects to any filing system is that you usually wind up with stuff that falls into more than one category, which means you have the dilemma on where to put it. Also, you find that there's a "miscellaneous" category for the stuff that doesn't fit into the other categories. And he's right: that pile ends up growing.
That's not to say that we should give up organizing all together. Just don't freak out when things aren't nicely fit into categories with 100% discrete grouping neatness. For people with OCDs, I know that that's easier said than done, and 90% just doesn't cut it, because it's not 100%. Well, it's still better than having only about 1% of your stuff organized, right? I'm sure I'll return to this concept in the future, because the topic goes deeper.
Well that's the only reason why I thought of the quotation. Now I'm going to babble about taxonomy in biology when I should be getting some sleep.
In older times, people had all sorts of ways of categorizing the different animals they saw. They may have grouped bats with birds, fungi with plants, or sharks with dolphins. It's understandable why people did that thousands of years ago when all they really had to go on were first-glance, external appearances. We know now from biology though that bats are actually mammals and thus much more similar to other mammals than they are to birds. We also know that fungi aren't really plants, and dolphins aren't fish.
The different taxonomy levels or taxa in biology, which form a nested hierarchy, are Domain, Kingdom, Phylum, Class, Order, Family, Genus, and Species. Humans for example are of the domain "Eukaryota" (we're eukaryotes, meaning our cells have a nucleus and organelles), specifically of kingdom "Animalia" (we're animals), Phylum "Chordata" (we're vertebrates, not invertebrates), Class "Mammalia" (we're mammals, more specifically), of which we're primates (the Order), specifically great apes (Family "Hominidae"), of the Genus "Homo", species "homo sapiens".
When I first learned the term "vertebrate" in grammar school science class, I wondered why we classified animals by whether or not they had a backbone. Why was the backbone or lack of it used to define the broadest of animal sub-categories, and not characteristics like color, size, or number of legs? Why do we use the system described above instead? Well as Dawkins said, this system "which springs from evolutionary biology" doesn't suffer the problem of having organisms that could fall into more than one otherwise unrelated category. That's because it's all based on common descent, with how things are related to each other. Traits are inherited, which means that some organisms are more closely-related than others. This system fits everything living now, and everything that has ever lived, into unambiguous categories.
The nice thing about Wikipedia's articles on different animals is that they include a column on the right showing the different taxa that the species belongs to. So you can click on each link to go up and down the different categories in the hierarchy. For example, go to the Homo Sapiens page, and try clicking on the right for "Primates", "Mammalia", etc.
Oh, and here's a helpful mnemonic for remembering "Phylum, Class, Order, Family, Genus, Species":