Mutual Mistake
Contracts & Sales · Lesson 13
Mutual Mistake
這一課問的是：當雙方對「基本假設」共享一個錯誤時，受重大不利之一方何時可主張撤銷合約？
Actor
Act
Object
Standard
Consequence
Core Terminology · 7 must-know
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mutual mistake
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Restatement §152: both shared a mistake about a basic assumption with material effect.
共同錯誤。
basic assumption
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Fact both parties tacitly built the deal on.
基本假設。
material effect
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The mistake significantly disturbs the agreed exchange.
重大影響。
risk allocation
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If risk allocated to one party, that party bears it.
風險分配。
Rule Sentence · the workhorse
Under mutual mistake, a party may avoid the contract where both parties shared a mistake about a basic assumption that has a material effect on the agreed exchange, provided that the adversely affected party did not bear the risk of the mistake.
Mini IRAC · build the Application
Issue. May the seller avoid a sale of "barren" livestock when both parties later discover the animal was pregnant and worth ten times the contract price?
Rule. A party may avoid a contract for mutual mistake where both parties shared a mistake about a basic assumption that materially affects the exchange.
Application (model). Both parties believed the cow was barren when contracting; in fact she was pregnant, making her worth ten times more. Because mutual mistake permits avoidance when a shared mistake about a basic assumption materially upsets the agreed exchange, the fact that the parties' common assumption about the cow's nature was wrong — and that the truth radically alters the value flowing each way — means the basic-assumption and materiality elements are satisfied.
Pick the right element for each blank:
g1.
g2.
Conclusion. Therefore, the seller may avoid the contract for mutual mistake.
Practice Drill · tap to build the rule
Drop the chips here in correct order:
Tap chips to add → tap chips in the target to remove: