The correct usage of ～と決める, ～に決める, and ～を決める

Question

Browsing the example of 決める, I found at least there are 3 patterns as follows:

• 行くと決めた。I decided to go.

• 行くまいと決めた。I decided not to go.

• 車を買うことに決めた。I decided to buy a car.

• 会議の日を決めた。I decided the meeting date.

Questions

• Are my conclusions below correct?

  • ～に決める can only follow こと.
  • ～と決める can only follow verb in dictionary form.
  • ～を決める can follow any noun.

• Which is the correct interpretation of「私たちは、会議の日を三月四日に決めた。」?

  • We decided the meeting date to be March 4.

  • We decided the meeting date on March 4. (But the meeting date is unspecified)

Answer 1

1. Basically you follow the next template:

(the thing/subject the decision is assigned to, i.e. the direct object) + を (what was decided to be) + に/と + 決めた

Based on this, we can also see this pattern:

(constant) + を (variable) + に/と + 決めた

• を is used to unite a transitive verb such as 決める with its direct object. It answers the question "What is subject to decision?".

• に among other uses marks a direction (we often use "to" as a translation); this direction can also point to intangible things like ideas or decisions, for example:

朝食をホットケーキに決めました。

More natural translation: I decided to eat hotcakes as breakfast.

More literal translation: I decided breakfast to (be) hotcakes.

We can then say に it will answer the question "What is the decision?".

• Now the use of と instead of に in the formula is tricky, it implies the subtlety of something "arriving to its final state". It will also answer "What is the decision?" but with a definitive tone.

We can see this behaviour as well with the verb なる in に + なる and と + なる:

やっと先生になりました！

I finally became a teacher!

やっと先生となりました！

I finally became a teacher! (Implying the speaker sees becoming a teacher as some sort of final stage, maybe it finally got a degree for becoming so after a long time and can finally begin to work).

2. Think about the above and you'll find the answer to your questions:

Are my conclusions below correct?

～に決める can only follow こと.

～と決める can only follow verb in dictionary form.

～を決める can follow any noun.

Answer is none of those conclusions is correct, the summarised pattern is as follows:

noun + を + noun* + に/と + 決めた

*Note: The second noun of the formula may not be a noun per se but a verb or even an adjective put in a "noun-form" with the help of things like こと, 連用形, 連体形 etc...

Which is the correct interpretation of 「私たちは、会議の日を三月四日に決めた。」?

The first one, following the patterns I showed you we can see that the meeting date was the subject being put to decision and that March 4 is the decision outcome.

Answer 2

The different particles used with 決める can express slightly different meanings. Just as in English there may be some overlap in how you can use them, but here are the primary functions of the particles as used with 決める.

(1) ～を決める
を marks the direct object of 決める. It merely tells us that something is being decided (without necessarily explicitly stating what the outcome of the decision was).

小説のタイトルを決めた。
I decided the title of the novel.

In this sentence you aren't saying what the title is, only that you have decided what it is. The title is the object of the deciding-action, hence it is marked with を.

会議の日を決める
to decide the date of the meeting

....................................................................................................................................

(2a) ～に決める
に is used to specify what the outcome of the decision was. Whereas を simply told us that a decision is being taken about something, に is used to supplement that information by explicitly stating what the result of the decision is. In other words, に marks the stated/named end result of the decision.

小説のタイトルを「ぼっちゃん」に決めた。
I decided on "Bocchan" as the title of the novel. 　　

会議の日を23日に決める
to decide on the 23rd as the date of the meeting

(2b) ～に決める
に can also be used to mark the time at which a decision is made. This is a standard use of に which is unrelated to your specific question. But for example:

今日中に決める
to decide today

..............................................................................................................................

(3) ～と決める
と is a quotative particle which tells us the content of whatever verb it is used with. ～と言った tells us the content of what was said. ～と思った tell us the content of what was thought. Likewise, ～と決めた tells us the content of what was decided (and it is expressed as a predicate when used with と).

小説のタイトルを変えると決めた。
I decided to change the title of the novel.

会議の日を変更すると決める
to decide to change the date of the meeting

This time, と is marking the clause which is reporting the content of the decision (expressed as one complete phrase).
....................................................................................................................................

To sum up, you can loosely define the different usages in English as follows:

～を決める to decide (something like a day, a time, etc.)
～に決める to decide on (a named outcome like a specific day, time, etc)
～と決める to decide to (+ predicate with contents of decision)