to do と doing の使い分け(核心の理屈)To Do or Doing? The One Idea That Sorts Them
不定詞・動名詞 / Infinitives & Gerunds
to do は「これからその行為へ向かう矢印」、doing は「すでに形のある活動そのもの」。この1つの理屈が、動詞ごとの丸暗記(want は to、enjoy は -ing…)のほぼ全部を説明します。このカテゴリの残りのエントリは、すべてこの原理の応用編です。
To do is an arrow pointing toward an act that hasn't happened yet; doing is the activity itself, already a thing. This single idea explains most of the verb-by-verb memorization (want takes to, enjoy takes -ing…). Every other entry in this category is an application of this one principle.
矢印の to、実体の -ing
The Arrow and the Thing
I want to swim.(泳ぎたい)——まだ泳いでいません。want の視線は未来へ向かい、to がその矢印です(方向の前置詞 to と同じ絵)。I enjoy swimming.(泳ぐのが楽しい)——楽しめるのは、実際に体験している活動だけ。-ing は行為を「名詞のような実体」に固めた形です。矢印か、実体か。動詞の意味がどちらを求めるかで、相棒が決まります。
I want to swim — no swimming has happened yet. Want looks toward the future, and to is its arrow (the same picture as the direction preposition to). I enjoy swimming: you can only enjoy an activity you're actually in. The -ing form solidifies the act into a noun-like thing. Arrow or thing: the verb's own meaning chooses its partner.
矢印と実体Arrows and things
I hope to see you again soon.
また近いうちに会えますように。
hope(願う)は未来向き=矢印の to。Hope looks ahead — the arrow.
I finished writing theなぜ the なのか【その場で一つに決まる】話し手と聞き手のいる状況で、どれを指すか一つに決まるから the。日本語なら「（例の）」「うちの」を補って読むと感覚が近い。 report.
レポートを書き終えた。
finish(終える)対象は進行中だった活動=実体の -ing。You finish an activity already underway — the thing.
She decided to move to Osaka.
彼女は大阪に引っ越すことに決めた。
decide(決める)も、これからの行為への矢印。Deciding aims at what's next — arrow again.
to do(矢印)
未来・意図・目標を見る動詞と組む: want / hope / plan / decide / promise。Pairs with forward-looking verbs: want, hope, plan, decide, promise.
You can only enjoy an activity that actually happens — there's no enjoying an arrow. So enjoy's partner is always -ing. Run it through the logic and the flashcard fact becomes obvious.
want to / need to / hope to〜したい/する必要がある/だといいな未来を見る動詞の3本柱。全部矢印の to。Three pillars of forward-looking — all arrows.
enjoy -ing / finish -ing〜を楽しむ/し終える実体を扱う動詞の代表。楽しむにも終えるにも、実物が要る。The thing-handlers: both need an actual activity in hand.
something to do何かやること名詞+ to do =「これからやるべきこと」。矢印が名詞に掛かる形。Noun + to do — the arrow aimed from a noun: things yet to be done.
worth doingやる価値があるworth は前置詞的に実体(-ing)を取る。It's worth trying.(試す価値はある)Worth weighs a thing, so it takes -ing: It's worth trying.
まとめ / Summary
to do =これからへの矢印、doing =すでにある実体。To do: the arrow ahead. Doing: the thing in hand.
未来を見る動詞(want / plan / decide)は to。Forward-looking verbs take to.
実体を扱う動詞(enjoy / finish / avoid)は -ing。Thing-handling verbs take -ing.
迷ったら「矢印か実体か」を自問。8割は理屈で当たる。Ask arrow-or-thing first — the logic wins 8 in 10.