〜ならいざしらず

Formality Level: Formal / Literary — editorial writing, formal debates, literary fiction, written criticism

Classical/Literary Origin: いざしらず is a classical Japanese expression combining いざ (an archaic exclamatory/transitional word, equivalent to "well now, as for") and しらず (the negative of 知る, "not knowing / I do not know"). Together, いざしらず means roughly "I don't know about that / leaving that aside / setting aside the question of." When preceded by ならば (conditional of なり/だ), the full phrase means: "Leaving aside whether ~ might be the case, [the main situation is different]." In modern Japanese, it has become a fixed concessive expression of formal register.

Structure

Form	Example
Noun + ならいざしらず	子どもならいざしらず
Plain verb/adj + ならいざしらず	知らないならいざしらず
[Understandable case] + ならいざしらず、[unacceptable case] + は...	初心者ならいざしらず、プロがこんなミスをするとは

The first clause (before ならいざしらず) presents a conceded case — something where the following outcome or behaviour might be understandable or forgivable. The second clause presents the actual situation, which is surprising, unacceptable, or incongruous given the speaker's higher expectations.

Meaning

"I can understand if it were ~, but (not this)," "one thing if ~ but ~," "granted that ~ might be different, but"

The pattern acknowledges that X (the conceded case) would be an understandable excuse or explanation — but the speaker is making clear that the actual situation is not X and therefore the behaviour or outcome is not acceptable, surprising, or noteworthy.

The critical implication is always: the actual subject or situation does not match the conceded case, and therefore a higher standard applies. If the conceded case is "a beginner," the actual subject is a professional. If the conceded case is "not knowing," the actual subject clearly knows. This gap between what would be forgivable and what is actually happening creates the force of the expression.

It carries a critical or condemnatory tone in many contexts and appears in formal writing where the speaker wants to distinguish excusable cases from those that are not.

Example Sentences

Japanese	English
子どもならいざしらず、大人がそんな言い訳をするとは情けない。	One could understand it from a child, but it is pathetic for an adult to make such an excuse.
初心者ならいざしらず、10年のキャリアを持つ彼がこのミスをするとは考えられない。	Understandable perhaps from a beginner, but it is inconceivable that someone with ten years of experience would make this mistake.
昔ならいざしらず、今の時代にこんな差別的な発言が許されるはずがない。	That might have been acceptable in the past, but in this day and age such discriminatory remarks should never be tolerated.
少額ならいざしらず、これほどの横領は組織的な犯罪と見なされる。	A small sum might be overlooked, but embezzlement of this scale is considered organised crime.
病気ならいざしらず、健康な人が毎日休むのは問題だ。	Illness would be understandable, but it is a problem for a healthy person to take time off every day.
緊急事態ならいざしらず、通常業務でこれだけの遅延は許容できない。	In an emergency it might be acceptable, but this level of delay in normal operations cannot be tolerated.

Common Mistakes

Using in casual speech: ならいざしらず is formal and written in register. In conversation, say 〜ならともかく (〜ならともかくとして) for a similar concessive meaning.
Confusing the logic direction: The clause before ならいざしらず is the forgivable/understandable case, not the actual situation. The actual situation is described in the second clause. Reversing these produces nonsense.
Confusing with ならでは: These patterns have completely different functions. ならでは expresses positive exclusivity; ならいざしらず concedes an understandable exception while rejecting the main case.

Compare With

Pattern	Register	Meaning	Key Difference
〜ならいざしらず	Formal/Literary	I can understand if ~ but (not this)	Formal; the forgivable case is explicitly named
〜ならともかく	Semi-formal	~ might be acceptable, but	More colloquial equivalent; very close in meaning
〜はともかく	All registers	Setting aside ~, at least	Broader; sets aside a concern without necessarily criticising
〜はさておき	Semi-formal	Leaving aside ~	Neutral; moves the topic rather than creating contrast
〜にもかかわらず	Formal	Despite ~	Contradiction of expectation without the concession structure