I've been trying to understand the age old question of が vs は recently. The
resources I've used so far have given helpful answers, but I'm still not
getting 1 key point. I'll summarize my knowledge so far:

Tae Kim (see [this](http://www.guidetojapanese.org/particles.html#part4) and
[this](http://www.guidetojapanese.org/blog/2005/02/05/the-difference-between-
and/)) points out that が is mainly an identifier particle, i.e. it identifies
new information. Makino and Tsutsui note this as well in their book (see
[this](https://www.amazon.co.uk/d/Books/Dictionary-Basic-Japanese-Grammar-
Seiichi-Makino/4789004546), pp118-20). [This excellent
post](https://japanese.stackexchange.com/questions/22/whats-the-difference-
between-wa-%E3%81%AF-and-ga-%E3%81%8C/51#51) on this site talks about it as
well and uses the concept of “universe of discourse” to indicate what can and
cannot use は and が. If it’s new, i.e. not in the universe of discourse, then
it uses が. If not, it uses は. None of these sources, while helpful, can fully
answer my questions however.

I'll give some examples that are confusing me. My potential solution is that
context determines when the bellow use は or が, but I don’t understand how it
would.

(a) The classic example of the beginning of a fairytale that many, including
Makino and Tsutsui, use [pp118-9]:

> 昔々一人のおじいさんが住んでいました。おじいさんはとても貧乏でした

This is perfectly clear. We don't know the old man, so he's introduced via が
and then は can and must be used. Same as in English the and a.

> There once was **an** old man. **The** man was very poor.

What confuses me, however, is generic nouns and some pronouns (see next
examples) where I can't use the "a and the" test.

(b) Makino and Tsutsui give the following example:

> 雨が降っている

I don’t understand here how 雨 constitutes “new” information. Makino and
Tsutsui say that は can be used with “generic nouns” that are not new
information by virtue of their being general knowledge (their examples are “車”
and “人”). Wouldn’t this include something like "rain"?

(c) In [this](https://japanese.stackexchange.com/questions/3214/extracting-
from-and-introducing-to-universe-of-discourse-using-%E3%81%AF-
and-%E3%81%8C-with-%E3%81%93%E3%81%9D%E3%81%82) Stackexchange post, Flaw
(question author) considers and example dialogue: "

> Person A: どちらが東ですか。Person B: こちら（ は / が ）東です。

This is an exercise, and according to the person answering the question, it's
が as こちら constitutes "new information". The answer there doesn't sufficiently
explain, for me to understand, why this is new information. As Flaw points
out, isn't this part of the environment the people are speaking in, and thus
context should give have introduced こちら already? Also, I don't understand in
general how a generic non question-word pronouns like こちら can be sometimes
"new" and sometimes "old" information (as both は and が are used with it at
different points). Questions words make sense, as they’re always unknown
information, but other pronouns (including things like 私) don't make sense to
me.

Again, my potential solution is that context determines when the bellow use は
or が, but I don’t understand how that would happen.

ありがとうございます! よろしくお願いいたします!
CC BY-SA 3.0
2017-02-10T21:07:49.500
43397
2017-02-12T02:31:07.310
2017-04-13T12:43:48.447
-1
18449
question
grammar particles particle-が
What is "new information" for が?
When you find a theory doesn't get along with what's observed in reality,
there's no point in sticking to that theory.

Cases where you should use が or other case particles without topicalized **in
a sentence** can fall into three categories.

  1. [Sentence of neutral description](https://japanese.stackexchange.com/questions/43213/can-someone-explain-me-the-use-of-%E3%81%AF-and-%E3%81%8C-in-this-sentence)
  2. Exhaustive listing
  3. A part of coherent sentences

Exhaustive listing

"It's apple that's red" can be translated into 赤いのは りんごだ, and you can rephrase
it as りんごが赤い. Likewise, うなぎは 私だ (it's me who ordered eel) can be rephrased as
私が うなぎだ. This kind of usage is called exhaustive listing.

Coherent sentences

Instead of saying 生徒が頭が痛いのでは 練習にならない (When pupils have headache, it can't be
enough training), you can express it as 生徒が頭が痛い、これでは練習にならない. Now, the part
生徒が頭が痛い in the second sentence looks a sentence without topic. But it's not
really an independent sentence per se.

In your examples, you can explain おじいさんが住んでいた and 雨が降っている with Sentence of
neutral description, and こちらが東 with Exhaustive listing (you can rephrase it as
東はこちら).
CC BY-SA 3.0
2017-02-12T02:31:07.310
43438
2017-02-12T02:31:07.310
2017-04-13T12:43:44.207
-1
4092
43397
answer