# 人間の平均寿命が100歳になったとしたら



## thetazuo

人間の平均寿命が100歳になったとしたら、人々は老後にどのようなことをしたいと考えるだろうか。

Hi. Would you explain why なった instead of なる is used here when humanity’s average life span reaching 100 is in the future?

Thank you.


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## kanadaaa

Because it's subjunctive.


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## thetazuo

Thank you, kanadaaa. I have never heard that there is subjunctive mood in Japanese. Could you please explain it in detail? Does Japanese subjunctive mood work in the same way as English subjunctive mood does?


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## kanadaaa

日本語 文法 条件：解説
This might help.


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## kanadaaa

And this might too:
英会話中級者の壁・仮定法の用法を徹底解説！ 日本語と比べて分かった、会話で仮定法を使いこなすための必須感覚とは？ | English Lab（イングリッシュラボ）┃レアジョブ英会話が発信する英語サイト


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## thetazuo

Thank you again.
The contents in the first link seem almost the same as my textbook, which doesn’t cover Japanese subjunctive mood.
The second link appears to be concerned with English subjunctive mood, not Japanese subjunctive, though it is written in Japanese. (Sorry, my Japanese is not good so I can’t quite read it)
Could you explain it in your own words?
I think in the op example, the first clause describes an imaginary/unreal future condition, so we must use the た form, just as we use past tense in English to refer to an imaginary/unreal future condition.
Right?


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## kanadaaa

Then, how about this?
～としたら/～とすれば/～とすると 如果(假如)…的話 @ 自分のために笑っていい。 :: 痞客邦 ::
I don't think tense is any relevant here. It just seems there are different patterns of conjugation for the verb preceding としたら.
(Technically speaking, Japanese doesn't have an explicit subjunctive mood, although it has many means of expressing subjunctive meanings. This would just complicate the matter, so forget about it.)


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## thetazuo

kanadaaa said:


> This would just complicate the matter, so forget about it.)


I’m not ready to memorize it.


kanadaaa said:


> It just seems there are different patterns of conjugation for the verb preceding としたら.


I get it. But if I were to forget about Japanese subjunctive, then how would I know when to use た form before としたら and when to use dictionary form before としたら?


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## kanadaaa

thetazuo said:


> how would I know when to use た form before としたら and when to use dictionary form before としたら?


Actually, both patterns are possible. The only difference is that the speaker thinks of the event described in the conditional as something that has already happened, or something that could happen in the future. So:

人間の平均寿命が100歳になるとしたら 
人間の平均寿命が100歳になったとしたら 

These are both good. And now I'm writing this, I think I can answer your question in #1.


thetazuo said:


> Would you explain why なった instead of なる is used here when humanity’s average life span reaching 100 is in the future?


This is probably because Japanese is a language that uses the absolute tense, unlike the relative tense in English.
What matters is how the speaker sees the event s/he is describing.
So the bottom line is, you can think of them as interchangeable, as long as としたら is used.


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## Flaminius

kanadaaa said:


> Japanese is a language that uses the absolute tense, unlike the relative tense in English.


これ、逆ではないですか?　英語が絶対時制を持ち、日本語は相対時制を持つとされることが一般的だと思います。


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## kanadaaa

Flaminius said:


> これ、逆ではないですか?　英語が絶対時制を持ち、日本語は相対時制を持つとされることが一般的だと思います。


逆ですね。すみません。


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## SoLaTiDoberman

人間の平均寿命が100歳になったとしたら、
I think なった is the "present perfect tense" (完了形) in English.

人間の平均寿命が100歳になったとしたら、
=人間の平均寿命が100歳になってしまっているとしたら、
＝人間の平均寿命が100歳になった、（そしてその状態が継続している）と仮定したら、
=人間の平均寿命が100歳が実際に達成された、実際にそうなってしまった、と仮定したら、
=人間の平均寿命が100歳というのがもはや当然の時代にすんでいると仮定したら、

人間の平均寿命が100歳になったとしたら、・・・*１*     (If the human life span *has (already or actually) reached* 100 years,)
人間の平均寿命が100歳になるとしたら・・・・・*２*  (If the human life span *reaches* 100 years,)

Both *1 *and *2* are more or less the same. They are conditional. They provide us with "assumptions."
"Assumptions" are not the real thing, but merely the "guesses" or the "conditions."
However, the assumption of *1* seems more real or realistic than that of *2*. We think of that condition more* vivid *and *really *because of the "perfect tense."　We suppose the long-lifespan society has really come.
Whereas,* ２ *is a mediocre, common or just conditional.
We may think that *1 *has higher possibility than* 2* somehow. (More precisely speaking, the possibility remains the same, but we think of the situation of that condition more vividly.)
Therefore, using the past tense in Japanese in* 1* and using the subjunctive past in English are rather_* even the opposite *_from a certain viewpoint.

仮定法過去 (the second conditional or the subjunctive past ) in English shows impossible things or unreal things. It indicates the speaker's desire or something. The possibility to attain the statement is very low or zero, actually.
However, the both *1 *and* 2 *in Japanese doesn't indicate that the possibility is high or low. They are basically *conditional*, "if."


In other words, both* 1 *and* 2* mean the same thing, but *1* is rhetorically better or more effective.
Anyway, not a few native Japanese speakers would prefer* 1* in this kind of context.
They choose* 1 *naturally without thinking.
I hope this helps.

『英語の仮定法』とは異なり、実際の達成度が低い仮定を述べるわけではない。つまり実現性が低い状況に言及しているわけではない。
過去形で書いても、現在形で書いても、条件節は条件節であり、その確率が高いとか低いとかの違いはない。単に仮定を書いている。
ただし、「過去形」で書い*た*方が、修辞的に、その仮定内容をよりリアルに感じる。よりありありと感じる。なぜなら実際に起き*た*あとの状況を想起させるからだ。
従って、この手の仮定を書く場合に「過去形」は日本語ではしばしば好んで用いられる。
（ただし、この差は微々たるもので、通常日本人はその差を意識しているわけではない。　以上、私見。）


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## thetazuo

Thanks a lot for the supplementary explanation!


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