若い時にいい友達『を』作ることはとても大事だ。
“It is very important to make friends when one is young.”
“To make” is not a noun, it's an infinitive. It should be “making friends” no? I understand that it turns the verb into a gerund, but why is it in the infinitive here? I don’t get it.
(Sentence is from the basic grammar dictionary).
P.s.: I know it says ことは but the example is listed under ことが in my dictionary.
Firstly, classing Japanese verbs can't be done in the same way as with English verbs. The linguistic terminology is generally different because of the incongruities between the languages. While you can call the English verb "to make" an infinitive, calling 作る or 作ること an infinitive is not quite correct. It is sometimes known as the Dictionary form, or Plain form, but Tsujimoto (1996) refers to these as verbs where the nonpast tense 'ru' is attached to verbal roots. While this may sound somewhat abstract, the broad definition reflects the wide range of usages observed in this verb category. It sometimes functions differently than infinitives function in English.
Secondly, こと in this context is generally referred to as a 'nominalizer', in that it turns the preceding phrase into a noun phrase which can then be modified in the same way nouns are. See this thread for a more detailed explanation of nominalizers in Japanese.
Finally, the は in this sentence seems to be a standard usage, as a topic marker. If this sentence was preceded by some contrastive statement, you could argue that it is a contrastive usage of は. Either way, it seems to be a normal usage. I think you would benefit from reading this thread which discusses the difference between the usages of は and が.
[An Introduction to Japanese Linguistics (Tsujimoto, 1996)]
