The Mood Marker ～のだ
In our first lesson on ～のだ, we learned how its fundamental usage is as a “scope marker,” and in doing so, we learned a lot about how sentences with ～のだ are similar and dissimilar to typical declarative (肯定文) and negative (否定文) sentences, based largely on predicate type and the kinds of complements (補語) present in the sentence.
To begin our discussion on how ～のだ may set the mood of the sentence, we will uncharacteristically start with the conclusion. Mood, in grammar, may be described as any inflectional ending that describes the speaker’s attitude toward the situation at hand. As such, “mood” is highly subject to context. In understanding how the mood marker ～のだ functions, much of our discussion will be how much of these following nuances are inherit to itself or borne from the context at large.
To play the devil’s advocate, though, let’s review once more what the terms “scope” and “mood” mean in the context of Japanese sentence structure and how that affects ～のだ’s placement in it.
Firstly, the nominalizing effect ～のだ has and its being part of the predicate are both intrinsic features. Secondly, Japanese sentence structure itself exhibits a strict hierarchy for what goes inside the predicate:
VERB STEM + VOICE + VOLITION + ASPECT + NEGATION + TENSE + MOOD
Meaning, ～のだ’s placement at the end both solidifies its position and functionality within a sentence. This can be demonstrated by the phrase:
食べられようとしていなかったらしいんだね .
Gloss: Eat-passive-volition-progressive-negation-past tense-mood (seems)-mood (reinforcement)-huh.
So it does seem (it) wasn’t trying to get eaten, huh.
Broken down, we have [食べ] as the verb root, [られ] a voice marker indicating the passive voice, [ようとし] indicating volition, [てい] indicating aspect, [なかっ] indicating negation, [た] indicating tense, and [らしい] indicates mood. It is arguably the case that [んだ]’s place in the predicate allows for it to function as a mood indicator.
Its nominalization effect on the conjugation chain is manifested by the copula portion in both its scope and mood marking renditions, but there are unique restrictions to the mood marker ～のだ not found with the scope marker ～のだ. That being said, keep the following points in mind when handling variations of the mood marker ～のだ.
- Because the mood marker ～のだ reflects the attitude of the speaker, minute differences and restrictions can arise from whether it is contracted or in a different speech register; meaning, ～のだ・んだ vs ～のです・んです will be a matter of contingency this time.
- As for whether だ is changed to dialectal variants such as じゃ・や, those will be treated as being synonymous.
- Unlike the scope marker ～のだ, tense as well as affirmation vs. negation may interact differently depending on how the mood marker ～のだ functions. Meaning, whether those conjugations make sense is entirely dependent on whether those concepts are compatible on a nuance-by-nuance basis.
Comparing The Two ～のだ:
Basic Grammar
The main goal of this lesson will be determining the fundamental essence of the mood marker ～のだ, which considering how many specific nuances were mentioned, will be an arduous task.
So far in this lesson, the one commonality that links the mood marker ～のだ with the scope marker ～のだ is that they are etymologically the same, and both possess the same conjugations, but the functionality of the mood marker ～のだ goes beyond making predicates behave more like noun-predicates.
Providing an “explanation” within context is the one-statement description for the overall template to using the mood marker ～のだ. The most typical examples do, in fact, behave like this. First, consider the following.
1. セス君？いないよ。出張に行ったんだ。
Seth-kun? He’s not here. He went on a business trip.
The mood marker ～のだ in Ex. 1 serves to demonstrate to the listener that [出張に行った] is the situation behind [（セス君が）いない].
Already, we see a subtle yet clear difference in function between the mood and scope functions of ～のだ. Instead of defining a Y1, which is at the foundation of the scope marker ～のだ, the mood marker ～のだ seems to relate its comment to the context at large.
Incidentally, we also see a major difference in particle usage within the dependent clauses made by these two different ～のだ regarding は vs が. In the case of the scope marker ～のだ, は must never be used, but this restriction does not exist for the mood marker ～のだ. This does not mean that は does not occur with the former. Rather, は cannot exist within the confines of Y in the sentence pattern XはＹだ as this pertains to the scope marker ～のだ.
In the following examples, to make identification easier, X for the main clause, if present, will be put in 【】and が・は inside dependent clauses will be greyed. The extent of influence ～のだ has will be denoted by [].
2. テイラー君から【返事】来ないね。[きっときょうは忙しい]んだ。(Mood ～のだ)
I haven’t gotten a response from Taylor-kun. I’m sure he’s busy today.
3. [氷河期が来た]のではない。[地球温暖化が進んでいる]のだ。(Scope ～のだ)
It’s not that we have come upon an ice age. The issue is that global warming is progressing.
4. 【鉢の土は】、湿った状態だったので、[水が足りなかったから枯れた]のではありません。(Scope ～のだ)
The soil in the pot was moist, so it didn’t wither because of a lack of water.
Another grammatical difference between the scope marker ～のだ and the mood marker ～のだ is that the latter freely attaches itself to nominal/adjectival-noun predicates, whereas the former stimulates that the redefining be on X (think back to Ex. 21 in our coverage here). That is not to say that the scope marker ～のだ is incompatible with these predicate types, as Ex. 5 is an example of it, but there is no such hurdle as demonstrated by Ex. 6.
5. 何もしないのが休憩なのだ。
Doing nothing is what is defined as a break.
6. いま休憩なんだよ！
I’m on break right now!
7. メール確認は休憩なのでありません。仕事なのです。△
Intended: Checking e-mails is not breaktime; it’s work. ?
Commonalities between both types of ～のだ can, though, be found in their shared use of the nominalizer の. One of which is that の makes the Y sound like an established entity, not reflective of a spontaneous matter.
8. どうしよう・・・うん、やっぱ行くんだ！X (Mood ～のだ)
Intended: What to do… Yeah, I will go!
The ungrammaticality of Ex. 8 is not due to やっぱ行くんだ itself being faulty, but that ～のだ (both types) is inappropriate for stating the speaker’s volition in real-time.
9. もう諒君には会うのではない。X (Scope ～のだ)
Intended: I’m not going to see Ryo-kun anymore.
This property is also what enables ～のだ (both types) to make third-person statements regarding thoughts and feelings, which is generally not done with predicate types in their basic iterations.
10. 諒君はきっと嬉しいんだ。(Mood ～のだ)
Ryo-kun is definitely pleased.
11. 思い出が悲しいのではない。思い出を美化するから、悲しいのだ。(Scope ～のだ)
It’s not that memories are saddening. It’s how (people) romanticize memories that is what is saddening.
Quote by 秋元康.
12. 私が悲しいのではない。悲しみが私に纏わりついて離れないのだ。(Scope ～のだ)
It’s not that I am sad; it’s that sadness clings to me and won’t let go.
2 Factors, 4 Combinations
Earlier, it was mentioned that the mood marker ～のだ inherently pertains itself to something the speaker views as an established situation, and with that in mind, consider the difference between the following.
13a. あ、雪が降ってる！
13b. あ、雪が降ってるんだ！
13a. Ah, it’s snowing!
13b. Ah, so it is snowing!
13a is a reflection of the speaker going outside and simply commenting on their discovery of it snowing. Meanwhile, 13b. recognizes the snowing as something that has been a thing, although they personally are just realizing this. While “snowing” is perceptualized as an “established situation,” it is not the case that there was any previous context that would have definitively indicated “snowing” as being established fact. This is important to keep in mind, because it throws a wrench in the notion that mood ～のだ simply associates a statement with prior context for some explanatory purpose. As such, we can view statements like 13b. as cluing us in to more so the speaker’s state of mind than anything. In this case, 13b. matches with the “exclamatory sense of discovery = 発見” nuance mentioned in the chart at the start of the lesson.
To account for all the nuances mood marker ～のだ has, two factors must be kept in mind. Insofar, these factors will be applied only to declarative sentences (平叙文).
- Whether or not mood ～のだ relates its statement to previous context. This can be viewed as the “why” behind mood ～のだ, and as we shall see, it is why ～のだ, as a whole, is understandably viewed as playing an “explanatory” role, even with statements in which the previous context is not pertinent to the remark made with mood ～のだ.
- Whether mood ～のだ presents a matter to someone else (interpersonal) or is instead directing attention to the situation itself with no intended listener (situation-oriented). This can be viewed as the “how” behind mood ～のだ. Putting aside whether or not previous context is pertinent, knowing whether the speaker is essentially talking to themselves or is explicitly seeking attention to their remark by a listener greatly determines how the remark is perceived.
Interpersonal VS Situation-Oriented
One striking difference between interpersonal mood ～のだ and non-interpersonal mood (=situation-oriented) mood ～のだ is that the latter does not pair well with polite speech registers, or with any tone adjustment, as the commentary is not meant to be directed at anyone.
14a. セス先生が来ないなあ。きっと用事があるの。??
14b. セス先生が来ないなあ。きっと用事があるんだ。◎
Seth-sensei hasn’t come, huh. He almost certainly has errands to do.
While the context may very well be an epiphany by the speaker on the matter at hand, and while the comment could be made within a back-and-forth discussion, lightbulb moments are more so for the speaker themselves mulling over the matter, and in doing so, the nuances （再）確認・ 発見 enumerated earlier are to be expected.
If situation-oriented instances of mood ～のだ are self-directed commentaries, we would expect for it to pair perfectly with ～と思う and the like, encapsulating the speaker’s mood within the speaker’s own thought. Conversely, that dynamic would result in an ungrammatical statement (or an unintended interpretation) if applied to interpersonal instances of mood ～のだ.
15. セス先生が来ないなあ。きっと用事があるんだと思う。(Situation-Oriented)
Seth-sensei hasn’t come huh. I think he almost certainly has errands to do.
16. 僕、明日は来ないよ。仕事があるんだと思う。(Interpersonal) Ｘ
I’m not coming tomorrow. I think it’s since I have work. X
17a. このスイッチを押すんだと思った。(Situation-Oriented)
I thought, yeah, I’d flip this switch.
17b. このスイッチを押すんだと思った。(Interpersonal) #
Intended: I thought, yeah, I’d flip this switch.
Result: I thought, “flip this switch!”
It goes without saying, though, that paying attention to context is of utmost importance. In isolation, non-interpersonal and interpersonal instances will often appear identical. Tonality alone may, though, be enough to delineate between non-interpersonal and interpersonal nuances most of the time. Even so, how the previous sentences or the situation in which the speaker finds themselves in matter at all would be left to speculation—speculation which Japanese discourse arguably necessitates. In other words, the “why” and “how” aspects of mood ～のだ are both being considered with what little or no context is being provided.
With all this being said, consider the following without context, and most importantly, without English translations, but with the likely nuances intended left in Japanese as hints.
18a. このスイッチを押すんだ。（確認・発見・強調・換言？）
18b. このスイッチを押すんだ！（決意・命令）
18c. このスイッチを押すんです。（決意）
18d. このスイッチを押すんです！（決意・命令）
Simplicity is only as simple as the context allows it to be, but that is where native-like intuition for deciphering even not-so contextualized contexts begins. In all four context-less scenarios, nuances are ruled out, which is a major takeaway.
Although 18a seems to have an array of interpretations, one can still surmise that the speaker is collecting their take on a matter with mood ～のだ, and the exact purpose (the “why”) would be made clear with preceding context or other outstanding factors, such as whether or not the speaker is alone, whether or not the speaker is talking (directly) to someone, or whether or not anything else had even been said. All these factors would be given facts pertaining to the discourse at hand and readably analyzed by the speaker and potential listeners.
Now let’s add minimal context. In doing so, we will see that not only does the nuancing of mood ～のだ become clear, if not outright obvious, but that that also necessitates that other nuances of mood ～のだ could highly unnatural, if not ungrammatical at worst as a result.
18e. そうか、このスイッチを押すんだ。
i. Oh, thus (X) flipping this switch. (再認識)
ii. Oh, you flip this switch. (発見)
iii. Oh, which is why you flip this switch. (確認)
iv. Oh, so flip this switch. (命令) X
v. Oh, you flip this switch (, so you know). (教示 ??・告白 ?? ・強調 ???)
Interpretations i-iii are all instances of non-interpersonal ～のだ, and while it may be vexing to be still left with multiple interpretations, external factors would otherwise assist. For instance, with i., knowing who the agent (=doer) is would tremendously help in knowing why the speaker is acknowledging flipping the switch has some importance in the overall scheme of things. As for ii., potential scenarios for how self-discovery on what happens when a certain switch is flipped comes into play are easy to imagine. Perhaps you are in a dungeon course, and you have been wondering how to get to the next room. You suddenly come across a panel and surmise that pressing the one with an ON/OFF switch will unlock some nearby passageway. iii. is more or less the same as i., but the epiphany is being attributed to outsider information. Someone else is present, but the actual statement is not being directed back at the listener to impose one’s own recognition of the matter to the entity that made it possible. Such a bizarre turning of the tables on what ought to be merely recognition of some greater importance on the part of oneself is precisely why v. is unnatural (but not entirely inconceivable). For instance, say そうか were not being used to acknowledge a previous statement but were more so indicative of a spur of the moment need to indicate that the statement marked by ～のだ is what the listener ought to hear – not to be confused with a lightbulb moment. In that scenario, what the speaker comes up with themselves could be pushed onto the listener as to what is the case or should happen, but the execution would still be unnatural, as all usages of ～のだ imply a certain level of conviction reflecting the speaker’s affirmation. Likewise, making an outright command (iv) in this manner remains ungrammatical, as commands made with mood ～のだ, while always interpersonal, do not occur out of the blue.
To visualize these two factors—interpersonal (対人的) and situation-oriented (対事的)—of mood ～のだ, the following chart illustrates them with directionality at the forefront. Rather than viewing them as opposing meanings, they are juxtaposed in a way that highlights how they relate to each other.
In a way, interpersonal ～のだ is like superimposing a thought bubble regarding a matter onto the listener, with the presumption that the listener does not know along with the assertion that the situation ought to be known or potentially dealt with (by the speaker and/or listener).
Incidentally, this presentation on the part of interpersonal ～のだ is not the same as merely presenting a fact the speakers knows that the listener happens to not know. In such a situation as that, we find that not using ～のだ is, indeed, the natural route. Consider the following.
19. 晩御飯も寿司だった。
Dinner was also sushi.
20. 自販機も便利だった。
The vending machines were also convenient.
21. 「セス先生、今度の旅行先はどこですか」「もちろん、東京ですよ」
“Seth-sensei, where are you going on your next trip?” “Tokyo, of course.”
When it comes to simple (adjectival-)noun predicates, presenting a simple answer (=statement), we see that while mood ～のだ is not present, the idea of presenting a situation to the listener is still at work, which in that sense, these sentences greatly resemble interpersonal mood ～のだ.
Similarly, a parallel connection can be made between situation-oriented mood ～のだ and (adjectival-)noun predicates, especially when rendered in their suppositional forms so as not to direct the statement back to the listener.
22. 「日本で地震が一番多いのはどこだろう」「うーん、恐らく福島県だろうな」
“Wonder where in Japan has the most earthquakes.” “Hmm, probably Fukushima Prefecture.”
23. 滋賀県の北西はどこだったかな。そうだ、琵琶湖だ！
The northwest of Shiga Prefecture, where was that? Oh yeah, Lake Biwa!
Even though there happens to be two speakers in Ex. 21, the response by the second speaker is directed toward the situation rather than the other speaker (=listener).
Now, in similar situations as is the case for the scope marker ～のだ, mood ～のだ also finds itself grammatically necessary, particularly with verbal predicates. While on the surface, the representation of verbs (=actions) may seem simple, on closer inspection, actions almost necessitate attention as to why and how the action is so, which is just the frame of mind for mood ～のだ to intervene. Next, consider the following.
24. 「昨日はどこに行ったんですか」「原宿に行ったんですよ」
“Where did you go yesterday?” “I went to Harajuku.”
25. 「テイラー君ったら、一体どこにいるんだろう」「うーん、きっと地元に行ったんだ」
Where on earth could Taylor be?” “Hmm, he must’ve gone back to his hometown.”
In Exs. 24-25, ～のだ is grammatically necessary. While ～のだ’s syntactic properties can be mostly attributed to the nominalization effect of の itself, the verbal dynamics at play, in tandem with the speaker’s mood toward the situation, make it quite different from basic noun-predicates seen in Exs. 19, 21-23. Moreover, mood ～のだ is fully capable of attaching itself to such (adjectival-)noun predicates, so that layer of meaning has to be accounted for.
By examining sentences like Exs. 21-23 in which mood ～のだ is not triggered, we see how when the speaker does emphasize the situation (事態) as being noteworthy, for whatever reason, be it to themselves (situation-oriented) or to the listener(s) (interpersonal), ～のだ obligatorily appears.
In pursuit of how this extra layer of meaning comes about, there is one grammatical feature that has yet to be mentioned, and that is allowing the particle は in clauses made with mood ～のだ, irrespective of part of speech. This property makes ～のだ syntactically different than typical embedded clauses in nominalized expressions3. Next, let’s look at another set of examples in which mood ～のだ’s presence does indicate more meaning than if it were omitted.
26a. 「Where are you from?」「アメリカから来ました」
26b. 「Where are you from?」「アメリカから来たんですよ」
Literally: “Where are you from?” “I came from America.”
“Where are you from?” “I’m from America.”
While either response is natural, 26b. is undoubtedly a more emotionally driven response than 26a, and the motive behind that kind of response is highlighting the fact presented to listener for whatever reason. Perhaps the second speaker is someone who just got off the plane, decked out in American flags, and is bringing attention to the situation [アメリカから来た] for personal PR.
27a. そうだ、月曜は閉まってるんだ。
27b. そうだ、月曜は休みだ。
27c. そうだ、月曜は休みなんだ。
That’s right, they’re closed on Mondays.
27a and 27c are synonymous and are semantically and syntactically equal. In both versions, the speaker’s thoughts toward the situation at hand help indicate that the circumstances involved are why the establishment is closed on Mondays. Meanwhile, 27b is merely a reminder of the establishment being closed on Mondays, with no hint as to how come.
Relating to Previous Context: Y/N?
Another factor behind mood ～のだ is whether or not the situation at hand which has not been recognized (hereby referred to as Q)—with the people not recognizing Q as such dependent on the previous factor—is presented as the meaning/situation behind a previous context (=what has been said or established to be so, hereby referred to as “P”). When combined with interpersonal and non-interpersonal contexts, the four outcomes that result are interpreted as follows:
The following four examples are representative of their respective combination.
28. テイラー君が来ないなあ。きっと何かがあったんだ。(Situation-Oriented, Q=P)
Taylor-kun hasn’t come, huh. Something must’ve happened.
29. 僕は明日は出勤しないよ。用事があるんだ。(Interpersonal, Q=P)
I’m not going to work tomorrow. I got errands to do.
30. そうか、ひっくり返して作るんだ。(Situation-Oriented, Q≠P)
Oh, you make it by turning it upside down.
31. 前へ進むんだ！(Interpersonal, Q≠P)
Keep moving forward!
The biggest question one might have from these examples is not whether previous context exists but if that might very well be the default assumption to understanding mood ～のだ in general. Generally speaking, P is not expressed within the same sentence as mood ～のだ. Going back to how the basic sentence structure is still XはYだ, in this light, [X=P] and [Y＋のだ = Q], and with X not present within the sentence, P and Q must be related.
To explain situations when P seems to not be present at all, P can be akin to the background situation. When the background is missing, the situation (Q) remains, and that recognition of Q, in a way, admitting that Q is there is like saying Q≈P.
When P is absent like in Exs. 30-31, indeed, there are still looming circumstances prompting the speaker to make these recognitions. In which case, if Q=P, then P need not be a verbal statement at all but can be more broadly defined as situational stimuli that constitute as information for establishing Q.
The one situation that may seem too incongruent with this analysis would be commands made with mood ～のだ. Yet, the mood behind said commands does indicate a greater meaning (context) than if one were to use the imperative form (命令形).
31a. このボタンを押せ。
31b. このボタンを押すんだぞ。
Press this button!
While both translate as “press this button!” in English, 31b gives the impression that the speaker has analyzed the situation and has determined that this command is what the listener ought to do. Perhaps, even, talk had been had that the speaker is privy to, which further prompted this command. In which case, the distinction between Pv and Pnv would be purely circumstantial to the point of being trivial. If so, we would imagine that there would be contexts in which delineating [Q=P] and [Q≠P] is difficult on face value, and lo behold, such contexts are quite common.
32a. 本、たくさん読んでるんだ（なあ）。
32b. 本、たくさん持ってるんだ（なあ）。
32c. 本棚が７つもあるんだ（なあ）。
32a. (He) sure reads a lot of books.
32b. (He) sure has a lot of books.
32c. Huh, (he) has seven bookshelves.
As context, imagine the speaker of Ex. 32 visiting Seth-sensei’s library. The room has seven bookshelves with many books, and these are 3 possible comments the speaker could make, all of which are situation-oriented and examples of talking to oneself.
Books are meant to be read. Walking in and seeing bookshelves with lots of books, knowing that one is visiting Seth-sensei’s library and how he must read for his profession, conversations that may have been had prior, etc. all constitute as Pv, with Pnv as an extra bonus upon seeing the library for oneself—thus also explaining why the speaker readily understands Q. Meanwhile, 32c feels more like just a response toward the visual information (Pnv). Now, as for recognizing “Seth-sensei having a lot of books” as Q like in 32b, whether Pv is involved is up in the air. The speaker presumably knows they are about to go to a library, but perhaps nothing about the library has ever been ascertained until entering its doors. With either scenario being equally plausible, and with 32c being just as valid as a response as 32a or 32c, where the speaker gets P may very well affect what the speaker ultimately states is Q; however, if P=Q, and if situations (Qs) can be multi-faceted, then this really is just nitpicking at P(n)3, with n standing for tackling what Q is from all possible angles.
関連付け ≈ 説明 ≈ 原因?
The use of 関連付け (association) to describe how mood ～のだ pertains to P, putting aside what P is, as opposed to 説明 (explanation), or 原因 (cause)/理由 reason, is for good reason. At the start of the lesson, the statement was made that:
Providing an “explanation” within context is the one-statement description for the overall template to using the mood marker ～のだ.
When in search for a one-statement description that account for the most instances, this statement can account for most nuances ascertained from it, but it still gets us quite far from explaining situations in which it indicates 決意 (determination) or a 命令 (command). However, it is tempting to go a step further down the oh-too narrow path by claiming that ～のだ—with no apparent distinction between its scope and mood functions—is a cause/reason marker.
33a. 私は傘を見てぎょっとした。一面にびっしょり黴が生えていたのだ。〇
33b. 私は傘を見てぎょっとした。一面にびっしょり黴が生えていたからだ。〇
33a. I was startled when I looked at the umbrella: it was completely covered in mold.
33b. I was startled when I looked at the umbrella; this was because it was completely covered in mold.
From 『哀しい予感』by 吉本ばなな.
34a. 私は言葉を止めた。彼女が突然顔を上げ険しい目をしたからだ。〇
34b. 私は言葉を止めた。彼女が突然顔を上げ険しい目をしたのだ。X/＃
34a. I stopping speaking. This was because she had suddenly looked up, her eyes grim.
34b. I stopped speaking. She had suddenly looked up, her eyes grim.
From 『むかし僕が死んだ家』by 東野圭吾.
35a. だから私は別のことを考えていた。人を殺せたらどんなにいいだろうと思っていたのだ。〇
35b. だから私は別のことを考えていた。人を殺せたらどんなにいいだろうと思っていたからだ。Ｘ
35a. That’s why I was thinking something else. I was wondering how nice it would be if I could kill someone.
35b. That’s why I was thinking something else. Because, I was wondering how nice it would be if I could kill someone. ??
From 『とり残されて』by 宮部みゆき.
36a. 階段から落ちた。怪我をしたのだ。#(???)
36b. 階段から落ちたから、怪我をしたのだ。◎
(Intended) 36a. I fell down the stairs. I was hurt.
36b. I hurt myself because I fell down the stairs. (Mood ～のだ)
36b. It’s that I hurt myself because I fell down the stairs. (Scope ～のだ)
Playing the devil’s advocate, we see that it is not terribly hard to find contexts in which ～のだ and ～から are seemingly interchangeable (Ex. 33). Interchangeability, though, never means that two phrasings are (exactly) the same. See also Ex. 37.
37.「いいよ、何の曲？」まさかユーミンじゃないだろうなと思いながら私は訊いた。昔よく聞かされたのだ。
From 『むかし僕が死んだ家』by 東野圭吾.
Even though the syntax of Ex. 33 and Ex. 34 are parallel, the grammaticality judgment is completely different. The reason for this lies in the fact that ～のだ cannot explicitly define causation. At most, the connection (=association) it does make is a vague relationship (漠然とした関係性) at best. In Japanese discourse, ～のだ may be substantiated from Pnv like in Ex. 32c, but in other instances like Ex. 38, it is only substantiated because of significant Pv.
38.「何か特殊な事情があって、君の幼い日の記憶が欠落している、そういうふうに君は考えているわけか？」自分の考えを整理しながら尋ねた。彼女は頷いた。それを見て私は言葉を繋いだ。「そうして、その記憶を取り戻すヒントが、この場所にあるかもしれないと期待しているんだな」テーブルの上の地図を指差す。
From 『むかし僕が死んだ家』by 東野圭吾.
Confusingly, perhaps, none of this excludes the reality that in many circumstances, the prior sentence (Pv) is more often than not efficient for mood ～のだ to be warranted, but the relationship presented by the speaker, for whatever reason, may never attain the status of [P=Q] = [Statement 1, therefore Statement 2].
39. 思わず、「なんだ、これは」と声を発していた。ドアの四隅が太いボトルと金具で固定されているのだ。
From『むかし僕が死んだ家』by 東野圭吾.
Now, you may have noticed that Ex. 34b and Ex. 36a were marked with #. For the intended meanings provided by Ex. 34a and Ex. 36b respectively, they would be ungrammatical. However, sense can be made of the statements. In both cases, Statement 1 cannot be substantiated as the cause for Statement 2. In Ex. 34a, the speaker stops talking because they notice how she is reacting. In Ex. 34b, “she” behaved that way, and the context for that is that the speaker stopped talking. In Ex. 36a, the speaker being injured is still being associated with falling down the stairs, but the association is not “falling down the stairs causing the injury”; instead, just like in English, it is unclear how or when the speaker got hurt as well as how falling down the stairs is involved with that assertion. People can still be unscathed from falling down stairs. A previous injury could have been a factor in falling down the stairs.
Let’s relate mood ～のだ back to “XはYだ” once more, but in the context of nominal predicates – given how nominal predicates state how the predicate equates to X. 寺村 (1984) points out that, principally, with mood ～のだ, PはYだ is no different than XはYだ. To demonstrate this, the following examples were raised:
40. あの音は何だ？
Response A: あれは鳩が鳴いている声です。
Response B: あれは鳩が鳴いているのです。
41. [Context]: Detective sees bloodstains on a suspect’s shirt)
これ（＝この血）は何だ？
Response A: これは自分の鼻血ですよ。
Response B: 鼻血がついたんですよ。
Response C: 血です。???
Response D: 血がついたんですよ。??
In Ex. 40, both responses identify what the noise (X) is, and in Ex. 40, we see how 何 (Y) can, in context, refer to the cause for X, and the same can be said about the various entities the word “what” can refer to in English. As for Ex. 41, this “what” (Y) that the detective wants to be identified by means of X is presented in a very simple format, and the same can be said of Responses A and B. However, while Responses C and D may seem simple, C does not truly answer the question as it pertains to the investigation, and D seemingly self-incriminates the suspect.
Insofar, we can surmise that [X=P] and [P≈Q], but that [P = reason, Q = result] is ungrammatical. Otherwise, the association denoted by mood ～のだ would have to that of cause-and-effect, which is not substantiated by Exs. 33-39, but Ex. 36 also taught us that P and Q cannot just be juxtaposed to be understood.
Given all this, how exactly is XはYだ any different than PはYのだ? One might argue that, for all intended purposes, grammatical limitations on the former necessitate the latter, and that the resultant sentence very much looks and acts like the former. This would explain why Responses A and B are so parallel in Exs. 40-41, but as far as how ～のだ ought to be defined, perhaps the answer is as simple as P (context) being defined as Q, in a parallel structure with its own flexibility.
In other words, as much as one might want X to stand for anything, nouns cannot stand for anything. Context at large, though, can stand for anything. When we wish to define that context, the inability of X to fulfill that role triggers the transformation of this basic sentence structure to PはQのだ.
Something we shall see in great detail in our third lesson on ～のだ, this triggering can even be combined together via dependent clauses as such:
42. [[ここまではわりにきっちりと書いてある = PA]。[ところが早くも飽きてきたのか = Q1 of PA]、[それとも書くことがなくなったのか = Q2 of PA]、ここで三日ほどブランクがある = PB]。[いきなり五月五月十二日になっているのだ = Q1 of PB]。
From 『むかし僕が死んだ家』by 東野圭吾.
Also note that, Y, in the context of XはYだ is also limited to nouns, so if an association is really being made between two thoughts, it ought not have that restriction placed on it. This may make you think, “well, what about nominalization? Is that not what ～のだ does to a Y?” That is precisely what happens, but it is crucial to note that nominalization is a transformative process. To see this in action, look no further than ～のだ predicates involving origin. Here, we see that XはYだ in its basic form of X and Y both being nouns is often impossible.
43. これは彼氏にもらったんだ。
This, I got it from my boyfriend.
44. これは彼氏の好きなものの中から選んだんだ。
This, I picked it out from the things my boyfriend likes.
While it may be obvious to state that XはYだ cannot be extended as is to accommodate more complex scenarios, through PはQのだ this is made possible, and through that means, the context is made clear through the use of ～のだ.
Incidentally, there are sentences in which X is a nominal phrase created through nominalization via の, but this is not so much problematic in determining how mood ～のだ functions. In this case X[～の] still gets transformed into a P that is then associated with a Q via ～のだ. Such sentences also indicate how scope ～のだ and mood ～のだ are ultimately, also, one and the same.
45. 制度に驚くのは、ものの考え方に驚いているのだ。
Their surprise in (that) system is that they are surprised at their way of thinking. (Scope ～のだ)
They’re surprised at their way of thinking, as far as their surprise in (that) system goes. (Mood ～のだ)
非関連付け → [Q≠P]?
Earlier, we probed whether instances of mood ～のだ which seemingly do not pertain to previous context truly are without some sort of context. In reality, the context is visual stimuli in the moment, and in this sense, we yet again see similarities with certain noun-predicates. Consider the following.
46a. あっ、雨だ。
46b. あっ、雨が降ってるんだ。
- Even so, XはYだ can still be seen as the basic sentence pattern for both the scope marker and the mood marker ～のだ. ↩︎
- Think back to how the particle は cannot enter the scope of ～のだ when used as a scope marker. In this light, the way in which the mood set by ～のだ extends over the whole statement, as opposed to being locally limited to some scope, is not limited to noun-predicate-like grammar. Moreover, embedded clauses which modify nouns do not allow topicalized items to be inside them, defaulting to only marking the nominative case with が・の. ↩︎
- Presenting grammar from a mathematical standpoint is incredibly helpful when understanding ～のだ as a whole. Complements are given letter substitutes, and differences in sentence structures (=equations) have to be accounted for so that the equations themselves do not break or contradict each other. Here, the issue really is what is Q, and by understanding Q, mood ～のだ’s meaning is ascertained. ↩︎