Can 故の mean "because" without a が preceding it?


I came across this line while reading a manga but was stuck on the 故の portion.

> 知識欲が行き過ぎた故の職業病なのぉ？

I understood this sentence as, "It's an occupational disease because of (your)
excessive thirst for knowledge."

However when I tried looking up for more sentences with 故の functioning as
"because", they all had が's before them. Furthermore, I read that 故の is also
not a term that'd be used in daily conversation, which has me puzzled since
this conversation is between two friends in a cafe.

Could it be that the が was simply just dropped because of the casual nature of
the conversation? Or does 故の mean something else in this context?




This 故【ゆえ】 is a special type of **noun** called 形式名詞 ("formal noun" in the
sense of "technically/apparently a noun"). Other formal nouns include とき, ため,
はず, etc.

Since 故 is a (formal) noun, something that modifies it must be an
**attributive** (i.e., "noun-modifying") expression. So what are "noun-
modifying" in Japanese?

  * Attributive form of an adjective 

> あまりに小さい故にむしろ不便だ。  
>  自由な故の悩み

  * Noun + の / No-adjective + の 

> 不勉強の故に分かりません。  
>  彼は軽い性格の故によくトラブルを起こしている。

  * Attributive form of a verb, a.k.a. a relative clause 

> 真剣に見る故に欠点も見えてくる。  
>  知識欲が行き過ぎた故の職業病

  * Lexicalized attributives (その, この, etc)
  * **Attributive form of a verb + が**

> 真剣に見るが故に欠点も見えてくる。  
>  知識欲が行き過ぎたが故の職業病  
>  小さ過ぎるが故に使いづらい。  
>  彼は軽い性格であるが故によくトラブルを起こしている。

The first four bullets should be easy if you understand 故 is technically a
noun. They are all valid usages of 故に/故の.

The last one may seem tricky if you don't know what's going on. This is a
special construction derived from Old Japanese. This が is actually a linking
particle like の, and the verb before it is actually a nominalized verb. Please
read: [Why is there a が in
深淵に臨むが如し?](https://japanese.stackexchange.com/q/70684/5010)

Since 故 is a stiff and literary expression, it still tends to be used along
with が when it is modified by a verb. But other simpler usages are also
perfectly possible. To put this simply, **the が between the verb and 故 is
optional**. In your case, there is another が near 故, so I even feel the
sentence sounds slightly better without が before 故.

Finally, it's not that odd to use 故の in casual conversations. Using a bit of
idiomatic expressions from archaic Japanese is usually natural. See: [Nuance
and conversational use of
なきにしもあらず](https://japanese.stackexchange.com/q/42718/5010)

