Recently I’ve found myself distracted (in a good way) from my translation work on from everywhere. by various papers and pages expounding on some of the more subtle bits of Japanese grammar. The fact that I actually enjoy reading admittedly dry texts in Japanese on such minutiae is yet more evidence that I really should go back to school one day and get, at the very least, a Master’s in Japanese. But for now, not having the requisite funding for another romp through academic wonderland, I’m placating my desire for a deeper understanding of Japanese with what is freely available on the interwebs.
Most of my informal study time of late has gone to the mystery that is ～のだ. Sadly, the students of Japanese with whom I’ve spoken have been rubber-stamped with the idea that this form merely expresses a reason for something. But even a cursory survey of real Japanese dialogue turns up places where this oversimplified definition falls short. Take the following from Vitamin M on October 9, 2007:
Clearly the ～のだ (～んです) in these sentences provides neither reason nor explanation. There is no cause-and-effect relationship that needs to be illustrated or proven. And so the explanation of ～のだ as giving a reason, which by now is a cliché (and a poor one at that) in Japanese language education, fails us completely in our attempts to rationalize this particular usage. The closest anyone can seem to get is to simply enumerate the multiple distinct uses of ～のだ, such as in this paper (PDF) from a 2009 symposium on Japanese language education held at Nagoya University. I have yet to see a simple, concise definition of ～のだ that covers all cases listed in the abovelinked paper, and seeing the continuing debate in the Japanese community (not to mention 7,000-yen tomes such as this one dedicated to the analysis of this elusive construction) leads me to believe that not even the Japanese completely understand their own language.
To be entirely honest, the issue of whether or not there exists One True Definition for ～のだ has no impact on my translation work. When ～のだ is used to give a reason, it simply translates as “since” or “because”. When used in other ways, it drops out entirely. ～のだ often has no impact on the English rendition for no other reason than the fact that English just doesn’t have a suitable equivalent. ～のだ is a delicate spice that appears only in minute quantities, and many times it has no place among the bold flavors of English.
So what then do you say to the student of Japanese when she runs into these delicate uses of ～のだ? That because it doesn’t translate into English, it means nothing and is therefore best ignored? This is nonsense. If it means nothing, it wouldn’t be in the sentence in the first place. There is no such thing as a grammatical element that lacks meaning, because the entire purpose of such elements is to convey meaning. Obviously something is being conveyed by ～のだ, but what? I may not possess a Ph.D. in Japanese, but my observations have led me to the following proposal:
～のだ is used to fill in (or acknowledge the filling in of) naturally occurring “information deficits”. Most commonly, the speaker uses ～のだ to give the listener information that is useful for understanding the rest of what the speaker is saying. In a sense, the speaker is anticipating what questions have appeared (or may soon appear) in the listener’s mind and answering them with ～のだ. This accounts for the common definition of ～のだ as giving a reason, since one of the most common questions the listener could ask is “Why?” But it also accounts for other uses, such as in response to the questions “What makes you say that?” and “So in other words, you mean…?” and “Why is what you’re saying relevant?”
Note that these “questions” may or may not be verbalized. Either the listener can choose to verbalize his question (with ～のか) and point out an existing information deficit, or the speaker can anticipate the questions and fill the deficit when needed. In the above example from Maaya, the two uses of ～のだ mark two pieces of information (the fact that she’s performing in Les Misérables, and the related fact that the character Éponine has long hair), neither of which are the main point of the paragraph but both of which will be useful for understanding the remainder. This lines up with another explanation of ～のだ I’ve seen (as to where, I’ve forgotten) which states that ～のだ shifts emphasis away from what precedes it and toward what follows (or in some cases, what came in an earlier sentence). Had she just launched into a statement of how that long hair isn’t her real hair without first filling in the information deficits, her listeners would have been confused. ～のだ fills in the contextual foundation in the listeners minds’ so they have a firm place to stand.
The use of ～のだ isn’t limited to the speaker providing information. It can also be used by the listener to confirm information : a sort of “curing process” for the information freshly poured into the information deficit. Take this conversation from another paper (PDF again) which goes over ～のだ:
Situation: A, who had left earlier to go buy something, comes back home, where B was the entire time.
B: 「あれ、どうしたんですか」 identifying an information deficit: I thought you went to buy something, so why are you back so soon?
A: 「お金を忘れたんです」 filling the deficit
B: 「あ、それで、もどってきたのですか」 acknowledging the new information and confirming that the dots in her mind are connected in the right way
These three sentences deal with the identification, filling, and curing of a single information deficit. In some cases the deficit is not filled with a direct answer such as in the above conversation, but rather the listener’s understanding of the speaker’s story leads the listener to a conclusion the speaker has not explicitly stated. In this case, the listener has filled her own information deficit, but she may choose to cure the information by asking for confirmation with ～のか, the interrogative form of ～のだ, as seen in the third sentence above.
This solves most uses of ～のだ, but we still have others to consider. First is the use of ～のだ in a command form. To illustrate this, I’ll borrow from this transcript of an episode of The Melancholy of Haruhi Suzumiya:
キョンの妹: ふわぁ、きょんくん何処行くの？ (information deficit)
キョン: 駅前。 (filled) 物を食べながらしゃべるんじゃありません。 (command)
(This particular line has stayed with me ever since I first saw this episode, partly because it sounded odd for Kyon to address his little sister with a polite verb form, and partly because this use of ～のだ as a command was a grammatical curiosity to me at the time.) If we want to explain this prohibition with an information deficit, we first have to identify the deficit itself. But where is it? Kyon’s sister (who is eating something during this scene) isn’t wondering if it’s OK to talk while eating. So we can’t explain this as Kyon giving the answer to an anticipated question in his sister’s mind.
But we can explain this if we recognize that when ～のだ is used as a command, the speaker is, in effect, creating the information deficit himself before filling it. The particulars of the deficit are left unspoken, but in the most generic sense, the speaker is giving an answer to the question, “What do you do in this situation?” In the above example, we can provide a more specific question: “What do you do while you’re eating something?” Kyon’s answer to fill this deficit is, “You don’t talk.”
The problem of the use of ～のだ to show strong intent is solved in a similar manner. Take the simple sentence 「勝つんだ！」. As above, when the information deficit to be filled by the use of ～のだ does not come from the listener, the speaker can, in some cases, supply his own deficit. In this particular use of ～のだ, because the speaker’s strong expression of will is intended to dispel any doubt, we can conclude that the information deficit is the question 「本当に勝つのか」. Whether or not this question exists in the listener’s mind is irrelevant; the speaker provides the question and then immediately answers it in a sort of preemptive strike against any possible information deficits.
This concludes my discussion of the function of ～のだ. I don’t know if this is the best explanation out there, nor do I know for sure that it applies to all cases. Either way, this is only half of the issue. The other half is to discover a way to teach Japanese language students how to use ～のだ naturally in their own speech. This goes beyond simply describing the function of ～のだ and into questions of how, from the perspective of a native Japanese speaker, sentences change when ～のだ is used versus when only ～だ is used. Why is it that some Japanese seem to use ～のだ in every other sentence while others hardly use it at all? How do you decide (in real time, as you speak) whether or not to end the sentence you’re in the middle of saying with ～のだ? I’m hopeful that this idea of information deficits leads to an answer to these questions, but I need some more time to think.