こと vs. の in this sentence

Question

This is kind of a follow-up question to this one: Problem with のが in this sentence

To give a quick overview, in this sentence そこで、マッカーサーが自分で作って見たのが地図Aである の　had a function I must admit I still can't really explain^^ To me it kind of works like a nominalizer, but if you follow the answers in the thread you will find that it is (also) something else.

However, I thought that this might be worth a new thread: Could one replace の with こと here? Both can be used as nominalizers, and maybe I can better differentiate between の as a mere nominalizer and の in the function of the respective construction above, if someone explains to me why こと can/can't be used here instead of の ^^

Answer 1

の is called a nominalizer when it turns a verb into a noun that means "(the act of) ～ing".

• 食べるのが好きです。
  I like eating.
• 明日寿司を食べるのを楽しみにしています。
  I am looking forward to eating sushi tomorrow.
• 晩ご飯を食べるのと風呂に入るの、どっちがいい？
  Which do you like, eating dinner or taking a bath?

This type of の is sometimes interchangeable with こと. For details see this question: What is the difference between the nominalizers こと and の?

However in cleft sentences の does not do that.

• 明日寿司を食べるのは太郎です。
  It's Taro who will eat sushi tomorrow.
• 明日太郎が食べるのは寿司です。
  It's sushi that Taro will eat tomorrow.
• 太郎が寿司を食べるのは明日です。
  It's tomorrow that Taro will eat sushi.
• 明日太郎が寿司を食べるのは銀座です。
  It's in Ginza (town) that Taro will eat sushi tomorrow.
• 明日太郎が寿司を食べるのは誕生日だからです。
  It's because it's his birthday that he will eat sushi tomorrow.

In the first sentence の is a placeholder for a person (Taro); in the second sentence, a thing (sushi); in the third sentence, a certain time point (tomorrow); and in the last sentence, a reason!

If you treated this の as a nominalizer, the first sentence would be translated as something like "[×] Eating sushi tomorrow is Taro," which does not make sense.

Finally, this type of の is not interchangeable with こと. You have to always use の to form a cleft sentence.

Answer 2

They are all natural as Japanese sentences and sound almost the same;

• そこで、マッカーサーが自分で作って見たのが地図Aである。
• そこで、マッカーサーが自分で作って見たものが地図Aである。
• そこで、マッカーサーが自分で作って見た地図が地図Aである。

But,

• そこで、マッカーサーが自分で作って見たことが地図Aである。 This is not natural as a Japanese sentence.