Using conditional 'ば'

Question

In this thread on japan-guide.com, we find two seemingly contradictory statements concerning the conditional particle ば.

One poster states:

If A & B are the same subject, B must be non-volitional. Otherwise, B can be volitional, e.g.:

[日本]{にほん}へ[行]{い}けば、[富士山]{ふじさん}がみられます

Another poster states that ば were used in expressions which reflect the speaker's will, judgment, permission, view, order or request, e.g.:

[安]{やす}ければ、[買]{か}います
[早]{はや}く[起]{お}きられれば、 [電話]{でんわ}をかけます/します

How do we reconcile these two statements?

Both do seem correct on their own.

Answer 1

Gramatically there is no restriction on volatility. Practically, however, the first presenter’s rule is partially correct.

If you say:

× 早く起きれば、電話します。

Japanese listener thinks:

It is you that decides whether to wake up early or not. Thus, you must know whether you will make a call or not.

On the other hand:

⚪︎ 早く起きられれば、電話します。

is acceptable, because you don't know yet whether you can wake up early or not.