In what contexts can "始{はじ}める" be an intransitive verb?

Question

"始める" is transitive while "始まる" is its intransitive form. In a textbook, I discovered:

(1) 知らないうちに、雨が降り始めていた。
(2) 明治時代の初め、日本は急速に近代化しつつあった。
(3) パーティをやっている最中に、急に雨が降り出した。

In each of those sentences, shouldn't an intransitive verb be used? Transitive verbs require direct objects. And, direct objects do not make sense with regard to "falling rain" and "the beginning of an era".

Are these sentence grammatically correct (but perhaps might sound unnatural)?

(4) 知らないうちに、雨が降り始まっていた。
(5) 明治時代の初まり、日本は急速に近代化しつつあった。
(6) パーティをやっている最中に、急に雨が降り出た。

In the same chapter, I read this sentence which makes total sense to me with regard to using the intransitive "始まる":

(7) 決勝戦が今、始まろうとしている。

How can I understand the use of transitive verbs in an intransitive context?

Answer 1

When used on their own, 始める and 出す are always transitive. However, when used as an auxiliary verb, 始める and 出す will always be used instead of their intransitive counterparts. The main verb, the verb that this helping verb attaches to, is the real determiner of transitivity. Transitivity has nothing to do with the auxiliary verb. For example, because 降る is intransitive, 降り始める will also be intransitive. On the other hand, 書く is transitive, so 書き始める is also transitive. The transitivity between the main verb and the auxiliary does not need to correspond.

始まる and 出る cannot be used as auxiliary verbs. It is just ungrammatical. 始める and 出す are used every time, as stated above.

As for 始め, that is its own word and is arguably separate from the verb 始める, and it can definitely be used where the verb would typically be intransitive. However, 始まり is also a valid word for "beginning", and the difference between the two is somewhat subtle and tough to explain (but I found an explanation here).