Why can に be put after a verb's plain form?

Question

I just noticed this line in the System Preferences app on OS X:

It says

変更するにはカギをクリックします。

Click the lock to make changes

Here, に is put after a verb's plain form. I have never seen this kind of usage before. As far as I know, に is a 格助詞. And 格助詞 don't connect to verbs. They only connect to 体言, which I think does not include verbs.

So i searched online to see if this is a usage that I am not aware of. And I found this. But that does not show any examples of this "verb plain form + に" usage.

It also says that

格助詞は、主に名詞について、その名詞と他の語（他の名詞、あるいは、述語としての動詞・形容詞）との意味関係を示します。

格助詞 is mainly put after a noun and shows the relationship between that noun and another noun, a verb used as a predicate or an adjective.

How can に be put after a verb's plain form? What is this usage?

Answer 1

The article you linked say a 格助詞 mainly attaches to a noun. And according to デジタル大辞泉, に is a 格助詞 which can safely follow a verb:

に

［格助］名詞、名詞に準じる語、動詞の連用形・連体形などに付く。

５ 動作・作用の目的を表す。「見舞い―行く」「迎え―行く」

I think you are already familiar with expressions like 食べに ("in order to eat") or 見に ("in order to see"), and these are the masu-stems of verbs followed by the 格助詞-に.

See also:

• What is the meaning of 「読むには読んだ」?

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By the way, this verb before に is actually in the 連体形 (attributive form), not in the 終止形 (dictionary form). 終止形 is, as the name suggests, for ending a clause/sentence as a predicate. On the other hand, 連体形 (despite its name) worked as a nominalized noun in archaic Japanese. We can still see the 連体形 of a verb used as a noun in proverbs. For example, 逃げるが勝ち = "Running is winning", 聞くは一時の恥 = "Asking is a one-time shame".

Answer 2

(1)変更するにはカギをクリックします。
(2)変更するためにはカギをクリックします。

Simply, the given sentence (1) is made of sentence (2) by omitting "ため". This kind of abbreviation is very common.

"ためには" means "in order to."