ではあるまいし
“It’s not as if X, so…” presents X as inapplicable and uses that premise to support a judgment, request, or explanation.
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The full form occurs in speech and writing; じゃあるまいし is conversational. It can support a request or rebuke, as in the examples, but can also explain the speaker’s or a third party’s actions or limitations. Unlike ならいざしらず, it presents X as inapplicable rather than setting X aside as a possible exception.
Do not assume the conclusion must be a rebuke or command addressed to the listener.
Note that the X clause presents a situation as inapplicable, rather than asserting it as a real fact.
- ならいざしらずN1「ならいざしらず」 leans literary and means “if it were X, that would be one thing,” using an exception as a contrast, and the following clause can be a negative judgment or an objective fact. 「ではあるまいし」 is colloquial, means “it's not as if X,” and is usually followed by a command, advice, or reproach, so the two should not be interchanged.
- からといってN2「からといって」 accepts the preceding clause but negates the conclusion or course of action drawn from it (“just because... doesn't mean...”), whereas 「ではあるまいし」 negates the preceding clause itself. The former is neutral in register and requires 「だ／である」 after a noun, so the two cannot be interchanged.
- くせにN3With 「くせに」 the preceding clause is a fact (“even though... and yet...”) and the pattern criticizes the mismatch between words and deeds, while with 「ではあるまいし」 the preceding clause is a premise that clearly doesn't hold (“it's not as if...”) followed by advice or a command. The preceding clauses are opposite in affirmative/negative polarity, so the two cannot be interchanged.
- ではないかN4「ではないか」 comes at the end of a sentence and is negative in form but affirmative in meaning, expressing confirmation, surprise, conjecture, or an appeal, with a written-style flavor; 「ではあるまいし」 is used mid-sentence, genuinely negates the premise, and is followed by reproach or advice. The two cannot be interchanged.
- とはN1「とは」 expresses surprise, deep emotion, or indignation at something unexpected and can end a sentence directly, while 「ではあるまいし」 negates a premise that clearly doesn't hold and is followed by a command, advice, or judgment. The former leans literary and the latter colloquial, so the two cannot be interchanged.
ならいざしらず sets X aside as a possible exception, while くせに criticizes despite a fact presented as real; からといって rejects an inference from a stated reason. ではないか asks or asserts “isn’t it?”, and とは can mark a topic or surprise; neither supplies this pattern’s “not X, so…” premise.
