Conflict among teachings of なら and ば

Question

I recently read a helpful answer on a question asking for clarification on the ways to say "if" in Japanese: と, たら, なら, ば. The link is here: Differences among -たら、なら、-んだったら、-えば, etc

According to the post, ば has the following rule: the later clause must be non-volitional unless a state verb like ある is used or the subjects of both clauses are different. なら is used when saying "Since A, then B" - A is an assumed context and B is a conclusion from A. This is supported by Tae Kim's lesson on conditionals: http://www.guidetojapanese.org/learn/grammar/conditionals

However, when encountering another website's take on なら and ば, I was surprised they grouped the two together, such that the rule on ば above applied to なら as well. http://www.learn-japanese-adventure.com/japanese-conditional-form-ba-nara.html

The only difference they seem to have stated was that ば is for verbs and i-adjectives, whereas なら is for na-adjectives and nouns. However, negative forms of verbs, i-adjectives, na-adjectives and nouns have ば (なければ).

1. In that website, why did they state that なら followed the rules of ば?
2. Why did they teach the V/i-adj and na-adj/N distinction between なら and ば?

Is there a way to resolve these conflicts?

Answer 1

In some sense, you can say なら is a subtype of ば. なら is ならば in its full form, and although this word makes no sense in modern Japanese, it did in olden times. Classical ならば is but a regular inflection of なり + ば, which rightly corresponds to today's であれば (である + ば).

So we can see that なら（ば） and ば don't really have differences in their meaning as conditionals, and what sets them apart is actually the である part.

            + なら            + ば
Verb        書くなら          書けば
I-adj       重いなら          重ければ
NA-adj      簡単なら          簡単であれば
Noun        彼なら            彼であれば

While verbs and i-adjectives can directly attach ば in their end, nouns and na-adjectives can't inflect by themselves, so they have to be aided by copula だ/である (~ "to be"). But the result is であれば, which has the exactly same meaning with なら! Therefore, we don't bother to use ば with those words for most of the time.

Only (the most of) verbs have actual difference between なら and ば. The reason is, verbs are events bound by the time, that is, A すれば B is only usable when A precedes B. なら, however, can lift this restriction by quietly nominalizing the verb (書くなら = 書くのであれば). With this, you're able to frame a phrase like 乗るなら飲むな, obviously "drive" comes after "drink". It also applies to i-adjectives, but since adjectives are states that don't have time limit, the meaning doesn't change very much.

But yet! なら and ば could make a large difference even with i-adjectives, because of diabolical argument-omitting of Japanese. When ば directly follows a verb or i-adjective, nothing happens. But なら can make a small seam that enables a hidden subject (or other) to intervene, during the nominalization of clause. That is:

かわいければいいよ。
As long as (she) is cute, I don't care.

かわいいならいいよ。
[Same as above] or As long as (you think) that (she) is cute, I don't care.

Answer 2

The way I've always known it is that なら means something along the lines of "if given..." and ば can be used to express any conditional statement in the present tense, which you have already found with the Tae Kim Guide. My use of HiNative has also backed this up several times over as native Japanese speakers have sided with and confirmed this meaning and usage for both of them. As for why this site groups them together, I do not have a clear answer, but I believe it to be because ば can be related to なら in some ways, but at the same time, they have their clear distinctions, as stated above.