Impracticability & Frustration
Contracts & Sales · Lesson 11
Impracticability & Frustration
這一課問的是：當合約成立後出現重大事件，使履行極端困難（impracticability）或使履行已無意義（frustration），承諾人是否被免除義務？
Actor
Act
Object
Standard
Consequence
Issue · what this lesson is really about
When a supervening event makes performance impracticable or destroys its purpose, is the promisor excused?
這一課問的是：當合約成立後出現重大事件，使履行極端困難（impracticability）或使履行已無意義（frustration），承諾人是否被免除義務？
Trigger words & phrases that should flag this issue:
firedestroyedwargovernment ordersupervening event
Core Terminology · 7 must-know
Tap a card to flip and reveal the meaning.
impracticability
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Restatement §261 / UCC §2-615: extreme &unreasonable difficulty from supervening event.
履行不能。
frustration of purpose
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Restatement §265: supervening event destroys principal purpose.
目的落空。
supervening event
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Event arising after formation that changes the situation.
事後事件。
basic assumption
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Fact whose continuing existence was a basic assumption of the contract.
基本假設。
foreseeability bar
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Foreseeable event generally bars excuse.
可預見性之障礙。
Rule Sentence · the workhorse
Performance is discharged for impracticability where a supervening event whose non-occurrence was a basic assumption makes performance extremely and unreasonably difficult or expensive; performance is discharged for frustration where such an event destroys the principal purpose of the contract.
Sentence Anatomy · 5 roles, 5 colors
Every rule sentence breaks into five visual roles.
Actor 行為人the promisor承諾人
Act 行為facing a supervening event面對事後事件
Object 對象performance · or its purpose履行或其目的
Standard 法律標準unforeseen + basic-assumption gone非可預見 + 基本假設失
Consequence 後果performance discharged履行免除
Casebook Snapshot · a real American case
Taylor v. Caldwell
Holding. Where the parties' contract presupposes the continued existence of a specific thing essential to performance, and that thing is destroyed without either party's fault, the contract is discharged.
Why it matters. When the world the parties contracted in disappears in a way neither caused, neither is bound.
雙方所預設之物消失（無人過失），合約即解除。
Common Mistakes · what trips students
✗ 「變貴一點」就是 impracticability。
✓ Must be extreme and unreasonable difficulty.
須極度且不合理之困難。
✗ frustration 與 impracticability 是同一個東西。
✓ Frustration = purpose destroyed; impracticability = performance impossible.
前者目的；後者履行。
Mini IRAC · build the Application
Issue. Is a concert hall's contract to host a singer excused when the hall burns to the ground a week before the show?
Rule. Performance is discharged for impracticability where a supervening event whose non-occurrence was a basic assumption of the contract makes performance extremely and unreasonably difficult.
Application (model). Without either party's fault, the contracted hall burned down a week before the performance. Because impracticability discharges performance when the destruction of the contract's specific subject removes a basic assumption, the fact that the contract presupposed the continued existence of the hall and that the hall has been destroyed means the basic assumption underlying performance has failed.
Pick the right element for each blank:
g1.
g2.
g3.
Conclusion. Therefore, the hall's performance is discharged.
MBE Check · multiple choice
B contracts with S in February for delivery of corn in October. In July, a severe but not unprecedented drought triples S's cost. S claims impracticability. What result?
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: