if I had done(過去への if) If I Had Known: The Unreal Past
仮定法 Conditionals & Subjunctive
「あの時こうしていたら」は if + 過去完了、帰結は would have done。If I had known, I would have helped.(知っていたら手伝ったのに)。過去の話をさらに一歩引くから過去完了——距離の原理はここでも一貫しています。
For "if things had gone differently back then," English uses if + past perfect, answered by would have done: If I had known, I would have helped. You're stepping back from a past that already happened — so the grammar steps back too, into the past perfect. The distance principle holds all the way down.
過去から、さらに一歩引く
One More Step Back from the Past
現在の非現実は過去形で引きました(if I had time)。過去の非現実は、過去からさらに引く必要があるので過去完了です(if I had had time)。帰結側も過去仕様になって would have done。「if 節は had done、帰結は would have done」——この対でワンセットです。
For an unreal present, we stepped back once — into the past form (if I had time). For an unreal past, we must step back from the past itself, which lands us in the past perfect (if I had had time). The result clause goes past-flavored too: would have done. If-clause had done, result would have done — learn them as a matched pair.
選ばなかったほうの過去 The road not taken
If I had left earlier, I would have caught the train.
もっと早く出ていたら、あの電車に乗れたのに。
実際は乗り遅れた。 In reality, you missed it.
If you had told me, I could have helped.
言ってくれていたら、手伝えたのに。
帰結は could have(可能の帰結)でも。軽い恨み節の定番。 Could have works too — the classic gentle reproach.
If it hadn't rained, the picnic would have been perfect.
雨さえ降らなければ、完璧なピクニックだったのに。
否定は hadn't done。 The negative: hadn't done.
if I did(今・これから)
今の別ルート。まだ想像の余地がある。 An alternative now — still imaginable.
If I quit my job, I'd travel for a year.
仕事を辞めたら、1年旅をするだろうな。
if I had done(過去)
過去の別ルート。もう変えられない。 An alternative past — sealed forever.
If I had quit back then, everything would have been different.
あの時辞めていたら、すべて違っていただろうな。
よくある間違い Common Mistake
If I have known, I would have helped.
知っていたら手伝ったのに。(のつもりで)
If I had known, I would have helped.
知っていたら手伝ったのに。
if 節の形は過去完了(had done)です。現在完了(have done)は「今につながる線」の道具で、仮定の過去には使えません。have と had の一字違いですが、役割はまるで別物です。
The if-clause takes the past perfect — had done. The present perfect (have done) draws lines that reach the present; it can't carry an unreal past. One letter apart, entirely different machines.
- If I had known, ... 知っていたら… 過去への悔いの開幕定番。後ろに would have が続く合図。 The standard opener of hindsight — a would have is coming.
- I would have loved to ... ぜひ〜したかった(のに叶わなかった) 実現しなかった願望の丁寧な言い方。誘いを逃したときの返事にも。 A graceful way to mourn a missed chance — perfect for declined-too-late invitations.
- couldn't have done it without you あなたなしでは成し得なかった 「あなた抜きの過去」を仮定して感謝を最大化する定番。スピーチの常連。 Imagines a you-less past to maximize the thanks — a speech-night regular.
- What would you have done? あなたならどうしていた? 相手を過去の分岐点に立たせる問い。物語・相談の定番。 Puts the listener at the fork in the road — storytelling's favorite question.
まとめ Summary
- 過去の非現実= if + had done、帰結は would have done。 Unreal past: if + had done, answered by would have done.
- 現在完了(have done)は使わない。had done。 Not the present perfect — the past perfect.
- 帰結は could have / might have にも交換可。 The result swaps freely: could have, might have.
- 聞き取りは「ウッダヴ(would've)」を待ち構える。 For listening, hunt the little would've.