Difference between using -ba or -ra form and と for conditionals?

Question

Is there some nuance between using each one?

For example:

Could I use と in place of -ba form in

電気を消せば暗くなる。

or in place of -ra form in

電気を消したら暗くなる。

like this:

電気を消すと暗くなる。

?

Answer 1

This is not meant as a rigorous translation template, but just a simplified illustration of the conceptual differences in your example:

1. P すれば Q　→　If P, Q will happen
2. P したら Q　→　When P, Q will happen
3. P すると Q　→　P, and Q happens

電気を消す → 暗くなる

1. 電気を消せば〜 (If I turn off the light, it will get dark)
2. 電気を消したら〜 (When I turn off the light, it will get dark)
3. 電気を消すと〜 (I turn off the light, and it gets dark)

お店に行く → ポスターをもらえる

1. お店に行けば〜 (If I go to the store, I will receive a poster)
2. お店に行ったら〜 (When I go to the store, I will receive a poster)
3. お店に行くと〜 (I go to the store, and I receive a poster)

食事をする → 元気になる

1. 食事をすれば〜 (If I eat, I will recover)
2. 食事をしたら〜 (When I eat, I will recover)
3. 食事をすると〜 (I eat, and I recover)

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In other words, (1) feels more strictly conditional, and (2) feels more temporal. In (3), your conviction in the inevitability between P and Q feels weaker, almost like you’re not really sure why or how P is causing Q. (This often resembles inductive reasoning, where you only know that “P results in Q” because of prior experiences.)

I guess the short answer is, sometimes they can be switched without a major shift in meaning, and sometimes not. Depends on what you're trying to convey.

Answer 2

To answer your question, No you can not use と in the first 2 sentences. To explain further, in Japanese, there are total 4 forms to explain the condition and its corresponding outcome. They are generally classified as follows:

• と
  Used to state natural consequences. In above example, getting dark is a natural consequence.

• なら
  Used to explain the contextual conditions. In short, it gives an answer to the question "What you will do if this context occurs?"

• ～ば
  Same as なら, but in formal way.

• ～たら
  Used to explain past conditions, as past tense ends with たら/ったら。