こそすれ〜ない

こそすれ〜ない is a literary or classical Japanese construction that contrasts two clauses, emphasizing a strong, often unexpected or contrary negation. The first clause asserts a strong affirmative or expectable tendency (often with nuance like “even if one says/does X” or “one would think X, but…”), while the second clause firmly denies a consequent action or state, typically translating as “but certainly not” or “even though …, … is not the case.” It is more formal and rarer in contemporary spoken Japanese, and you will usually encounter it in literary prose, historical texts, or stylistic writing. The first part uses the plain form (often V連体形 or V終止形) and the second part is a negative statement. The nuance can convey resignation, irony, or a decisive stance. Typical contexts include literary descriptions, formal speeches, or when contrasting expectations with reality. Important to note: this pattern is relatively old-fashioned and may sound unusual in everyday conversation.