The confusion about moe
Pondering the meaning of moe 「萌え」 sounds a bit 2005, back when the word qualified as a popular phrase in the Japanese media. Nowadays, it's become pretty uncommon among otaku to say that you're moe for such and such, as the term has been somewhat bastardized by mainstream exposure, or has simply fallen out of fashion (angry rants of English-speaking bloggers notwithstanding).
Still, there are no convenient replacements for at least some uses of the word moe. For example, the most concise answer I can give when somebody asks what kind of manga or anime I like is moe-kei. It's quite precise and widely understood (well, not in the general public of course, but the right answer if a Japanese person that isn't an otaku asks about your tastes in anime is more along the lines of “I've heard about that Studio Ghibli thing and what they do looks pretty cool”).
It's possible that some of you have dismissive comments to make about the previous sentence. Like “moe is not a genre, it's a feeling” or “your moe need not be the same as the next person's moe” (or “so you like moe shows, you sick pedo bastard”, but that's not the problem I'm interested in here). And that is right to some extent, but in this case, it misses the point. You see, the main reason why heated semantic debates about moe have continued mostly unabated throughout the decade is that different people use the term in different contexts to mean different things, and there are relatively authoritative examples of multiple usages.
Unlike such a word as otaku, which many people misuse simply because they're clueless (the folks over at OEG are spot on), moe really has several loosely related meanings even to people who know what they're talking about. You could argue that there is a one true original definition of the word, but even if that definition could be stated unambiguously, which is highly dubious, insisting that it is the only proper way to use moe is risibly pedantic.
In the interest of clearing up some confusion in the moe debate, but mostly for future reference (so that I can use the word later and make it clear what I mean by it), I'd like to review some of those multiple meanings, hopefully the most important ones. It's probably going to be half of the story at best, as I am only familiar, if that, with the male side of things. There is also a female usage of the word which I am in no position to discuss.
1. Moe is an affectionate feeling for a 2D character
This is probably the original meaning of the word. Moe is an affectionate feeling experencied by otaku towards a fictional character in anime, manga, games, etc., or towards the idealized persona of an individual like an idol or a seiyuu. The precise nature of that feeling is a subject of unending contention, and it was probably pretty vague in the first place, but commonly cited traits include “protective instinct”, “longing for youthful innocence”, “being overwhelmed by sheer cuteness” or “nostalgia”.
Some argue that you cannot really understand the moe feeling without experiencing it first hand (and that it is a significant aspect of the contemporary otaku identity). Others discuss at length whether moe is asexual or loaded with lustful desire (and the answer probably is that it can be both, even for the same person towards the same character, just at different times; this inconsistency runs deep in the otaku psyche), or how it relates to real love. And quite a few people also have cheap laughs at those grown-up guys who so obviously can't get laid.
The stereotypical way to express this feeling is the interjection moe~. It is occasionally used in writing, but pretty much no one actually says it aloud these days, despite a popular media cliché dating back to Densha otoko. There is some evidence that people would go moemoe~ at certain seiyuu events in the late 90s, but the stereotype is now thought of as mildly insulting nonetheless. What remains in current use, although it is going out of fashion as well, is the verb moeru, as in Taiga ni sugoku moeru yo “I feel so moe for Taiga” or Michiru ruuto kouryaku shita; moeta na “I completed the Michiru route; it was moe!”.
When the term gained popularity, it was also applied derivatively to not only fictional characters but pretty much anything, like railroad moe. But then it only really means “(perhaps slightly unhealthy) fondness for”, which is not a terribly useful definition, and only adds to the general confusion.
2. Moe is an aesthetic
Characters prone to elicit moe feelings in otaku tend to share common physical and emotional features that are expressed visually and/or narratively in creators' works and recognized as such by consumers. These features, such as child-like, somewhat abstract female cuteness, purity or emotional fragility constitute the moe aesthetic, which is not only a set of specific graphic idiosyncracies, but a general sense of the beautiful. In fact, the narrative attached to a character is probably the more important factor in eliciting moe; the character's representation, if any, serves to provide visual cues to this (possibly implied) narrative.
As an aside, while it is quite clear that emotional fragility or insecurity is a core element of the moe aesthetic, it would be wrong to assume that moe characters are by and large weak, or that moe otaku are on a power trip to dominate vulnerable little girls. On the contrary, moe girls often cope with their insecurities in a remarkably strong-willed manner, and it is this contrast that is endearing, rather than fragility itself (think of how popular tsundere characters are, for example).
Note finally that this aesthetic is colored by a strong sense of impending loss (which is sometimes compared to traditional Japanese concepts like wabi-sabi and mono no aware, but it can just as well be related to Victorian aesthetics). Youthfulness and purity are either transient or sealed in eternity by tragedy. An important theme of moe narratives is the desperate attempt to preserve this transient ideal for just a little longer—what Shingo calls “narrative stasis”.
3. Moe is a genre
In principle, you could feel moe about any fictional character, irrespective of the work it appears in, but for the most part, characters prone to elicit moe are designed as such, in works that purposefully conform to moe aesthetics. Manga editors, for example, are keenly aware of what constitutes moe-kei manga and what doesn't. Publishers organize their magazine line-ups along such distinctions.
For example, Tamagomago tells the amusing story of Tachibana Shiu, who presented her manga project to an editor of Manga Time Kirara (probably the most famous moe-kei 4-koma manga magazine, publishing such titles as Hidamari Sketch, Kanamemo and K-On). The editor took a five-second look at her drafts and immediately redirected her to Manga Home (another 4-koma magazine of Houbunsha which has a “family-oriented” perspective), where her manga is now serialized.
4. Moe is a way of constructing stories
In addition to general adherence to moe aesthetics, the moe genre has established a number of conventions for image reading. As I mentioned earlier, graphic elements in a moe image serve as visual cues to character narratives: they are interpreted as such in the framework of generic conventions. A girl with a zettai ryouiki, a stern look on her face, crossed arms and twin tails is most likely a tsundere. These various visual elements may have some sort of fetishistic appeal of their own, as so-called moe youso, and they can be combined into signs that convey actual narrative meaning.
This leads to a somewhat combinatorial approach to creating moe narratives—by putting together moe youso in a way that produces meaning, as described in a somewhat deconstructionist fashion by critics like Azuma Hiroki. Detractors argue that this can only result in shallow characterization and unoriginal storytelling, and there has been many humorous descriptions of how this can all go very, very wrong, but skilled writers have used this technique to commendable ends, much like constrained writing can result in beautiful novels.
5. Moe is a cash-cow
This is probably a case of nonsense by people who don't know what they're talking about, but when the word moe attracted media attention, it began to be used as a business keyword for anything vaguely related to otaku culture, from maid cafes to the Ghibli museum and trading card games. People wrote books about how the “moe market” in “moe moe Japan” was worth 2 trillion yen, and how the Japanese economy would be saved by otaku. Fortunately, it was a fad and died out (I think).
A related but more durable trend is the idea that you can stick the word moe, or a drawing of a moe girl, on pretty much any product, and it will sell like hot cakes among otaku. What started the trend is probably Moetan, ostensibly an English-learning manual with super cute drawings by POP and lots of otaku lingo. Moetan is humorous and not actually meant to teach you English, but it sparked a slew of self-teaching manuals about all sorts of (vaguely nerdy) subjects that were basically normal textbooks with a few cute girls thrown on top (think of the Moe moe guide to Unix network administration).
Nowadays, the focus has shifted to self-help, especially in the romantic department (Moe moe dating guide for 30-year old virgins; that's not exactly what the title means, but it's a pretty accurate rendition of the idea ^^), as well as products that aren't even books. If you get an illustrator like Nishimata Aoi to draw a cute picture of a moe girl on your bag of rice, you can expect sales to increase sevenfold.
6. Moe is a way of life
That's a silly and half-joking way to put it, but you can identitify a system of “moral” values borne out of moe aesthetics, especially as regards conscionable ways to conduct romantic relationships. You can probably draw a parallel with how medieval courtly love (fin'amor) originated in courtly romance as a literary form, in reaction to the somewhat brutal and unsophisticated relationships between men and women that were common at the time.
I'm not sure how widespread this idea of moe as a way of life is, but it has a rather high-profile advocate, Honda Tohru, who sees moe and contemporary otaku culture as a reaction against the venal, materialistic debasement of romantic relationships that occurred in Japan during the bubble and the subsequent lost decade. In short, better live happy and contented among cute videogame girls and body pillows than participate in the travesty that relationships with real women have become.
Which sounds like a nice conclusion (orz