What's the difference between ように and ことに? What if you add the te-form?


I am quite confused regarding the differences between the usages of ように and
ことに when they precede する/なる. Here are some examples:

  * 忘れ物をしない **ように** しましょう
  * 忘れ物をしない **ことに** しましょう

In the previous example, I would think that in the 1st sentence the speaker
would want the listeners to make sure there wouldn't be anything forgotten,
while in the 2nd they would want the listeners to pay attention or to make an
effort to not forget anything. Which makes sense to me because ようにする seems to
have the meaning of "ある状態にする", while ことにする seems to have a meaning of
"決意・努力をする" (please do tell me if I'm wrong). However, I can't tell the
difference between the two if する is in continuative form, like in the
following example:

  * 私は毎晩寝る前に日記を書く **ことに** しています
  * 私は毎晩寝る前に日記を書く **ように** しています

When the following verb is なる, on the other hand, I can't tell the difference
at all. For example, what's the difference between the following pairs of
sentences?

>   * ここの電気は人が通るとつくようになっています
>   * ここの電気は人が通るとつくことになっています
>

>   * 田中さんは家庭の事情で中国旅行には参加しないことになりました
>   * 田中さんは家庭の事情で中国旅行には参加しないようになりました
>

What are the differences between ように and ことに?




In general, ～ようにする is simply about making/keeping something in(to) some
state/situation described by the preceding verb. ～ことにする is about making a
decision/rule/resolution.

  * 見えるようにする to make it visible
  * 見えるようになる to turn/become visible
  * 見えることにする to decide to make it visible
  * 見えることになる a decision is made to make it visible

* * *

Now let's look at each example:

>   * 忘れ物をしないようにしましょう。
>   * 忘れ物をしないことにしましょう。
>

The former is the natural choice. The latter means something like "Let's (make
it a rule) not to forget anything (from now on)", which is an odd statement.
It sounds like it was fine to forget something until now!

>   * 寝る前に日記を書くようにしています。
>   * 寝る前に日記を書くことにしています。
>

These are mostly interchangeable. The よう version is a neutral description of
the speaker's habit. The こと version sounds a little stricter, like this is a
private _rule_. See also: [ことにする versus
ようにする](https://japanese.stackexchange.com/q/42581/5010)

>   * ここの電気は人が通るとつくようになっています。
>   * ここの電気は人が通るとつくことになっています。
>

The former is a neutral description of this mechanism. The latter implies "the
light is supposed to be turned on" or "the rule is that this light will be
turned on." When I hear something like this, I would wonder if the light is
not working.

>   * 田中さんは家庭の事情で中国旅行には参加しないようになりました。
>   * 田中さんは家庭の事情で中国旅行には参加しないことになりました。
>

In this case, the こと version is the natural choice because it's about
someone's decision. The former is not wrong, but may sound like someone is
dodging responsibility. You have to use ようになる when you describe a natural
phenomenon (e.g., 冬が近づき、夜に冷たい風が吹くようになりました).




In general, ～ようにする is simply about making/keeping something in(to) some
state/situation described by the preceding verb. ～ことにする is about making a
decision/rule/resolution.

  * 見えるようにする to make it visible
  * 見えるようになる to turn/become visible
  * 見えることにする to decide to make it visible
  * 見えることになる a decision is made to make it visible

* * *

Now let's look at each example:

>   * 忘れ物をしないようにしましょう。
>   * 忘れ物をしないことにしましょう。
>

The former is the natural choice. The latter means something like "Let's (make
it a rule) not to forget anything (from now on)", which is an odd statement.
It sounds like it was fine to forget something until now!

>   * 寝る前に日記を書くようにしています。
>   * 寝る前に日記を書くことにしています。
>

These are mostly interchangeable. The よう version is a neutral description of
the speaker's habit. The こと version sounds a little stricter, like this is a
private _rule_. See also: [ことにする versus
ようにする](https://japanese.stackexchange.com/q/42581/5010)

>   * ここの電気は人が通るとつくようになっています。
>   * ここの電気は人が通るとつくことになっています。
>

The former is a neutral description of this mechanism. The latter implies "the
light is supposed to be turned on" or "the rule is that this light will be
turned on." When I hear something like this, I would wonder if the light is
not working.

>   * 田中さんは家庭の事情で中国旅行には参加しないようになりました。
>   * 田中さんは家庭の事情で中国旅行には参加しないことになりました。
>

In this case, the こと version is the natural choice because it's about
someone's decision. The former is not wrong, but may sound like someone is
dodging responsibility. You have to use ようになる when you describe a natural
phenomenon (e.g., 冬が近づき、夜に冷たい風が吹くようになりました).

