This phrase means 'exactly because of X, Y happens'. It shows X is the only reason for Y.
... こそ ... Verb [已然形]Primary
... こそ ... い-Adjective [已然形]
... こそ ... Noun / な-Adjective [stem] + なれ
This phrase means 'exactly because of X, Y happens'. It shows X is the only reason for Y.
命あってこその物種なれ。
It is precisely because one has life that other things have value. (proverb)
厳しい冬を越してこそ、春の喜びは格別なりけれ。
It was precisely because we endured the harsh winter that the joy of spring was exceptional.
君でなくてこそ、この大役は務まらね。
Precisely because it is *not* you, this great responsibility cannot be fulfilled.
逆境にこそ人の真価は試されれ、順境では見えぬものがある。
It is precisely in adversity that a person's true worth is tested; there are things that cannot be seen in favorable times.
たゆまぬ努力をしてこそ、真の成功は訪れれ。
It is only because of tireless effort that true success arrives.
This pattern shows something will definitely happen. It is like saying 'for sure' or 'no doubt'. The first part makes the second part true.
This grammar is like 'kara koso' but more formal. It is different from 'ba'. 'Ba' just says 'because X, Y'. This grammar says 'X is the *only* reason for Y'.
Don't use this when you are talking to friends. It sounds very old-fashioned. This grammar is mostly for books. You will see it in old stories. You might also see it in formal speeches. It is not for daily chat.
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