～ば vs ～ていれば in counterfactual conditionals


In [l'électeur's answer
here](https://japanese.stackexchange.com/questions/25179/past-unreal-
conditional), he claims (with such confidence that he **bolds** the belief)
that the correct way to say the English sentence

> "If I had turned right back then, I wonder what would have happened."

is

> あのとき右に曲がっ **ていれば** 、どうなっ **ていた** だろう。

It seems like the reason for his statement is that instead of the plain ~ば, it
should instead be ~ていれば (and that なった should be なっていた).

Furthermore, according to 新完全マスター, for 反実仮想 either ～ば or ～ていれば is acceptable.
Yet, they only give examples of the latter, indicating that the latter form is
preferred.

> 言葉の使い方にもう少し注意し **ていれば** 、誤解されないで済んだものを。

Note that in this case, the second clause is plain past tense.

My questions are then:

  1. Why is it preferred to use ~ていれば for counterfactual conditionals instead of the plain ~ば? 
  2. Should we use the ~ている for both the **_if_** clause and the **_then_** clause or does the **_then_** clause not matter? 
  3. Is there a difference in meaning between the two grammatical forms or is it just a clarity of writing thing?

Note: I realize that this isn't limited to ~ば and seems to apply to ~たら and
～なら as well, but for the sake of an easier title I chose to talk specifically
about ~ば vs ~ていれば.




A simplified answer is that ていれば is most commonly used for past perfect
counterfactual.

The following is the most standard translation pattern (terminology as per
[Wikipedia](https://en.wikipedia.org/wiki/Counterfactual_conditional)).

  * (Irrealis) If you **paid** enough attention (now), you would notice (now). （今）よく注意 **すれば** 気づくのに
  * (Past perfect) If you **had paid** enough attention (then), you would **have noticed** (then). （あのとき）よく注意し **ていれば** 気づい **ていた** のに
  * (Past perfect - irrealis) If **had done** shopping yesterday, I wouldn't have to go out today. 昨日買い物し **ていれば** 今日出かけなくてもよかったのに.

So roughly, irrealis corresponds to れば and past perfect ていれば.

* * *

That said, perhaps due to the general sloppiness of Japanese in tense
expression, I think both can be used to some extent. E.g., the first sentence
of the question can be あの時右に曲がればどうなっただろう.

Also some verbs always require ている in some contexts and some cannot be
followed by ている. E.g. _if I had money_ and _if I had had money_ both become
金を持っていれば/金があれば (never 金を持てば/あっていれば).

