Is a settlement valid when the exact measure is knowable by one party but unknown to the other?

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Settlement is invalid if the subject matter is something they can both ascertain, such as an existing estate, or if one party knows the amount owed while the other party is ignorant of it. Ahmad disliked settling with a widow regarding her dower amount if she did not know what her husband left behind, referencing the statement of Shurayh to the same effect. This is because settlement was permitted in cases of ignorance due to necessity—to absolve liabilities and end conflict. Where knowledge is possible, there is no necessity for a settlement based on ignorance, and thus it is invalid, analogous to invalidating a sale in such a situation. When one party knowingly exploits the other's ignorance about a known asset, the intent is seen as unjustly diminishing the right, not resolving a dispute.