Double subject construction?


I've recently been having trouble with constructions that seem to mark two
subjects in the same clause. I've only encountered them in ～の方が...
constructions, but I can't seem to make sense of them grammatically. Here are
some examples:

>   1. 当然、都心より郊外のほう **が** 家賃 **が** 安い。 (from a vocabulary book)
>   2. （人）よりも自分の方 **が** 知識 **が** あると思う (from アルク)
>

My questions are: why are two subjects allowed here, and are there other
constructions in which this happens? So far my thoughts on this are:

(a) 方 seems to be a subject, but not have a verb. So maybe this is simply be
some kind of relative-clause-like construction with the noun elided away, e.g.
家賃が安い[ところだ] and 知識がある[人だ]. But this seems a little odd - I don't know of
anywhere else where this is possible.

(b) The second sentence might bracket as （人）よりも自分の方が([blah]と思う), rather than
(（人）よりも自分の方が[blah])と思う. This makes perfect sense, but I suspect that the と思う
could be removed to leave a valid sentence, so this explanation seems a little
spurious. In any case this doesn't explain the first sentence.

So I'm a little confused. Any light anyone can shed on this would be great.
Thanks!




As @Flaw flawlessly explains, Japanese sentences can have clausal predicates.
This is what causes what is commonly known as double-subject constructions,
although I believe "clausal predicates" really illustrates the structure
better.

I assume you have heard constructions like

> 彼は髪が長い He has long hair

Some teachers/textbooks might explain this away by saying that 彼 is a topic,
not a subject, but that creates problems when you run into sentences like

> 彼が髪が長いんだ！ He is the one with long hair!

Here the first が is an exhaustive-listing が. When multiple がs occur in a main
clause, the first is usually exhaustive-listing. Note that 髪が長いのは彼だ might be
more common, but I don't consider the above ungrammatical. Also,
dependent/relative clauses cannot have topics, so you might see

> 彼が髪が長い理由は ... だ The reason for his long hair is ...

although I think in this case 彼の髪が長い理由は...だ might also be as/more common.

In your example sentence, のほう needs to have a が (This would also fall under
the exhaustive-listing category) to have the comparative meaning

> 郊外のほうが家賃が安い Rent is **cheaper** in the suburbs

Changing the が to a は would lose the comparative meaning

> 郊外のほうは家賃が安い Rent is cheap in the suburbs

As a side note, I'm not exactly sure what the function of のほう would be in this
case, I think you can see it either as a filler, or as something that directs
your attention to 郊外. 郊外は家賃が安い would mean almost the same.

To address Billy's question in his comment

> 郊外が家賃が安い It is in the suburbs that rent is cheap

is grammatical, but quite narrow in meaning. And again, 家賃が安いのは郊外だ is probably
more common to convey this meaning.




As @Flaw flawlessly explains, Japanese sentences can have clausal predicates.
This is what causes what is commonly known as double-subject constructions,
although I believe "clausal predicates" really illustrates the structure
better.

I assume you have heard constructions like

> 彼は髪が長い He has long hair

Some teachers/textbooks might explain this away by saying that 彼 is a topic,
not a subject, but that creates problems when you run into sentences like

> 彼が髪が長いんだ！ He is the one with long hair!

Here the first が is an exhaustive-listing が. When multiple がs occur in a main
clause, the first is usually exhaustive-listing. Note that 髪が長いのは彼だ might be
more common, but I don't consider the above ungrammatical. Also,
dependent/relative clauses cannot have topics, so you might see

> 彼が髪が長い理由は ... だ The reason for his long hair is ...

although I think in this case 彼の髪が長い理由は...だ might also be as/more common.

In your example sentence, のほう needs to have a が (This would also fall under
the exhaustive-listing category) to have the comparative meaning

> 郊外のほうが家賃が安い Rent is **cheaper** in the suburbs

Changing the が to a は would lose the comparative meaning

> 郊外のほうは家賃が安い Rent is cheap in the suburbs

As a side note, I'm not exactly sure what the function of のほう would be in this
case, I think you can see it either as a filler, or as something that directs
your attention to 郊外. 郊外は家賃が安い would mean almost the same.

To address Billy's question in his comment

> 郊外が家賃が安い It is in the suburbs that rent is cheap

is grammatical, but quite narrow in meaning. And again, 家賃が安いのは郊外だ is probably
more common to convey this meaning.

