How to parse 「月日の経つのは早いものだ」

Question

月日の経つのは早いものだ。

From left to right, the first の marks a genitive case and the second one acts as a nominalizer. This means that the nominalized clause 経つの is being modified by 月日, forming a noun phrase 月日の経つの.

月日の経つのは早いものだ。

lit. The passing of time is quick!

However, we could replace the first の with が, which changes the meaning a bit:

月日が経つのは早いものだ。

lit. Time passing is quick!

Because of this, we may think that we have a relative clause although that would require a noun to modify. To be more precise, that would require the second の to be an indefinite pronoun, meaning something like "the one", which wouldn't make sense. 月日が経つの is simply a nominalized clause.

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In short,

• [[月日]{Noun}]の[[経つの]{Nominalized clause}] = [月日の経つの]{Noun Phrase}. The の in bold acts as a genitive case particle.
• [[月日が経つ]{Clause}]の = [月日が経つの]{Nominalized clause}. The の in bold acts as a nominalizer.

Where's the relative clause?

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By the way, I think 速い is also possible because we're describing its "quickness".

Answer 1

1. 月日の経つのは早いものだ。
2. 月日が経つのは早いものだ。

These sentences are syntactically exactly the same. Changing の to が doesn't change the meaning of the sentence a bit. The particles after 月日 are subject markers, and 月日{が/の}経つ is fundamentally a relative clause that modifies の (which is a noun).

Have you wondered why there is something called "ga-no conversion" in modern Japanese? You may believe が is the subject marker and の is the genitive case particle, but this distinction is rather new. In the past, these were almost the same particle. Both could mark a subject, and both could work as a possessive particle.

• Why can の and が both mark subjects in relative clauses?

  Old Japanese, as far as we can tell, didn't have a dedicated subject marker - if you wanted a subject that wasn't the topic also, you just left it unmarked. It had two genitive particles, though, *nə and *ŋga (modern の and が); which varied according to a kind of animacy hierarchy - *ŋga with personal pronouns and names IIRC (I've forgotten some of the details), *nə with the rest.

• 「が」vs「の」 with possessives
• Why is there a が in 深淵に臨むが如し?
• 【古典】古文の格助詞「が」「の」(主格・連体修飾格・同格)

Although が and の have become very different in modern Japanese, this is why they are still interchangeable inside "relative clauses".

And the concept of "relative clauses" is a bit broader than the English equivalent. What you know as nominalizers and cleft sentences are actually a special type of relative clause! Ga-no conversion works also inside these constructions, as shown below (S = subject marker, A = attributive form of a verb/adjective/copula, N = modified noun):

• 太陽が^S昇る^Aの^Nを見ていた。
  太陽の^S昇る^Aの^Nを見ていた。
  I was watching the sun rising.
• 彼が^S来る^Aの^Nは知らなかった。
  彼の^S来る^Aの^Nは知らなかった。
  彼が^S来る^Aこと^Nは知らなかった。
  彼の^S来る^Aこと^Nは知らなかった。
  I didn't know that he would come.
• 彼が^S知っている^Aこと^Nを教えてください。
  彼の^S知っている^Aこと^Nを教えてください。
  Please tell me what he knows.
• 彼女が^S1読んだ^A1の^N1は表紙が^S2赤い^A2本^N2です。
  彼女の^S1読んだ^A1の^N1は表紙の^S2赤い^A2本^N2です。
  It is a red-covered book that she read. (cleft sentence)
• 月日が^S1経つ^A1の^N1が^S2早い^A2こと^N2が^S3嫌いな^A3理由^N3が^S4分からない^A4人^N4が^S5した^A5質問^N5
  月日の^S1経つ^A1の^N1の^S2早い^A2こと^N2の^S3嫌いな^A3理由^N3の^S4分からない^A4人^N4の^S5した^A5質問^N5
  a question made by someone who doesn't understand the reason why some people dislike the fact that time passes quickly

Notice the S-A-N pattern seen consistently in these examples. Don't mix the の as a subject marker (marked with S) and の as a formal noun (marked with N).

So, after looking at these examples, haven't you started to think it's not very meaningful to treat one as a subject marker and the other as a genitive case particle? I'm not suggesting you should stop using the term nominalizer, but it's worth knowing all of these are ruled by the same principle.

Answer 2

の has the function of indicating subject (see #2 in the link), so both can be considered as Time passing is quick.

To me, 月日の経つのは... and 月日が... are both fine. In relative clauses modifying a noun, it is largely interchangeable even if one or the other can sound less idiomatic.

Examples：

• 彼の書いた本を読んだ = 彼が書いた本を読んだ
• 君の言うことはもっともだ = 君が言うことはもっともだ

'Counter-example' from here

• Aさんが私に書いた地図 but ✕ Aさんの私に書いた地図

I think the Aさんの... version is still grammatical and acceptable, but definitely less common.

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[Edit]

I think an (reverse) argument which won't be helpful for learners is that the second parsing is correct (or at least more natural) exactly because 月日が and 月日の are both possible.

Either way, the subject of 経つ is 月日 and the first parse won't change that and does not affect the meaning. (Kind of relevant: An English He insisted on my reading his new book, where my is semantically the subject of reading)

The case for 高田さんが使っていたのを覚えていますか is a bit different mainly because 使う is transitive. It is actually ambiguous between

• Do you remember that Takada-san was using it?
• Do you remember the one Takada-san was using?

In English, the bold it can't be omitted but in Japanese それを is omitted in the first reading. For this example 高田さんの... is possible but strongly suggests the second reading.

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Regarding 早い/速い for time, both may be used, but my feeling is 早い being more common. Cf 時間が経つのは「早い」「速い」どっち？. After all, a day passes per day...

A general distinction is to use 早い for early and 速い for fast.

Answer 3

Whether the article is が or の, native speakers see it this way.

［月日が／の経つ］の

Having said that, though, I think I know where your doubt is coming from.

Let’s consider the following example.

君が飲むのは分かる。

This sentence can be understood as meaning either of the following two.

I know {what/which/the one} you (are going to) drink.

I understand {that/why} you drink (something).

Now, look at the following sentence, where が is replaced with の.

君の飲むのは分かる。

This sentence sounds natural, at least in everyday conversation, only in the first sense. The second の is interpreted as an indefinite pronoun referring to a concrete thing, in this case a particular drink.

In the second interpretation of 君が飲むの, on the other hand, the final の means either “the fact” (こと) or “the reason” (理由) depending on the context. I suppose the reason 君の飲むの sounds unnatural in this sense is that the association between 君 and that の (for こと or 理由) is not direct enough to be naturally connected with の.

In your example, the final の in 月日が／の経つの is understood as meaning something like “the way” (様子) or “the pace” (早さ). It is the way or pace of time, making the linking with の sound natural enough. In fact, you could say 月日の様子 or 月日の早さ, although what the first phrase means is not clear without the verb 経つ.

Let’s look at one more example.

君が怒るのは分かる。

Like the example with 飲む above, this sentence could also be understood in two ways, although most people would understand it in the second meaning unless context suggests otherwise.

I know {what/which/the one that} angers you.

I understand why you get angry.

Curiously, 君の怒るの doesn’t sound quite natural even in the first sense. In the example with 飲む, the pronoun の represented a drink, and it was your drink (君の飲み物). In this example, however, it represents something external that causes a certain emotion in you. If we had to paraphrase it, it would become something like 怒らせるもの／やつ. I suppose this is too distant from 君 for the two to be naturally connected with の.

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[Edit]

As I suggested at the beginning of this post, you should still read 月日の経つの in the following structure .

［月日の経つ］の（＝様子／早さ）

Here, 月日 does work as the subject with respect to the verb 経つ much as in 月日が経つの. (There is no other function it can play within the brackets, after all.)

However, I think it would be fair to say that we do kind of feel the implicit association of 月日の様子／早さ transcending the boundary of the brackets. What I am claiming is that if this association cannot be felt, の may not sound as natural as が. This is also the case when the clause is long and の is far away from the modified noun (or nominalizer).