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It's not like this is science fiction with 〜じゃあるまいし

Grammar Explanation: It's not the case with 〜ではあるまいし

Manga panel from 名探偵コナン showing example of It's not like this is science fiction with 〜じゃあるまいし.
名探偵コナン » Volume 3 » Page 147

Evidence piles up for Ran that Conan, the smart young boy staying with her family, may actually be Shin’ichi, her missing childhood friend. She’s convinced that he’s Shin’ichi on the inside, but the sticking point is how he went from being a teenager to a child.

欄(らん):
「ＳＦ(エスエフ)じゃあるまいし…」
“It's not like this is sci-fi.”
「こんな不思議(ふしぎ)な事(こと)ってありえない…」
“Such an incredible thing is inconceivable...”

Key Points

  1. じゃあるまいし = it’s not as if

    • This is a colloquial form of ではあるまいし.

    • Ran is rejecting the idea by saying “it’s not like this is science fiction”.

  2. The expression dismisses a comparison as unrealistic

    • She brings up science fiction as the kind of world where such a thing might happen.

    • Then she uses じゃあるまいし to say real life is not that kind of setting.

See Also