Definition
An impossible contract is one that the law will not enforce because performance of the consideration — or a material term — is incapable of being carried out, either as a physical fact or as a matter of law. The impossibility may exist at the time the contract is formed (original or inherent impossibility) or may arise after formation due to a supervening event (subsequent impossibility).
Two distinct categories operate under this label:
1. Originally impossible contracts: Agreements void from formation because the subject matter does not exist, cannot exist, or is legally prohibited at the moment of contracting. A contract to sell land that the seller has no power to convey, or to deliver goods that were already destroyed before the agreement was made, falls here. These agreements are generally treated as void, not merely voidable — no binding obligation ever arose.
2. Subsequently impossible contracts: Contracts that are valid when formed but become incapable of performance due to a later event beyond the parties' control — destruction of a specific subject matter, death of an essential person, or a supervening change in law. These discharge the parties from their obligations rather than rendering the contract void from the outset.
Bouvier draws a precise distinction: strictly speaking, only contracts whose consideration is impossible are truly "impossible" in a legal sense. A promise may be difficult, costly, or even practically unachievable, but unless performance is genuinely impossible — not merely inconvenient or unprofitable — the contract remains binding.
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Common Confusion
IMPOSSIBLE CONTRACT vs. IMPRACTICABLE CONTRACT: Modern contract law has largely moved away from "impossible contract" as a working term, absorbing much of its function into the doctrines of impracticability and frustration of purpose. Commercial impracticability (codified in UCC § 2-615 and reflected in Restatement (Second) of Contracts § 261) does not require literal impossibility — it requires that performance has become commercially unreasonable due to an unforeseen contingency. Researchers should not assume that a historical source discussing impossible contracts maps cleanly onto modern impracticability doctrine. The standards differ, and the outcomes can diverge significantly.
IMPOSSIBLE CONTRACT vs. ILLEGAL CONTRACT: An illegal contract — one prohibited by statute or public policy — is sometimes loosely described as "impossible" because the law forbids performance. This is legal impossibility, not physical impossibility. Bouvier and older authorities treat the two as related but distinct. An illegal contract is void on grounds of public policy; a physically impossible contract is void because no real obligation was ever created. Modern sources treat these as separate doctrines entirely.
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Core Elements
For a contract to be discharged or voided on grounds of impossibility, courts historically and modernly have examined:
1. Genuine impossibility: Performance must be objectively impossible — not merely more difficult, more expensive, or less profitable than anticipated. Subjective inability (a party lacks the skill or means) does not qualify.
2. No assumption of risk: The party seeking discharge must not have expressly or impliedly assumed the risk of the supervening event. Express force majeure clauses, course of dealing, and the nature of the transaction all bear on this element.
3. Unforeseeability (for subsequent impossibility): The event rendering performance impossible must not have been reasonably foreseeable at the time of contracting. If the risk was foreseeable, courts expect it to have been allocated in the contract.
4. Causation: The impossibility must go to the heart of the agreed performance, not a peripheral obligation.
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Why It Matters in Research
The phrase "impossible contract" is predominantly a term of historical legal usage. Researchers working in pre-twentieth-century sources — including Bouvier and contemporaneous treatises — will encounter it as the standard framing for what modern doctrine calls impossibility of performance, impracticability, or frustration of purpose. These are not interchangeable concepts, and mapping historical analysis onto modern doctrine requires care.
Bouvier's entry is notably truncated in surviving editions, cutting off mid-sentence on the distinction between types of impossibility. Researchers relying solely on that entry will miss the full doctrinal architecture. The cross-reference to "IMPOSSIBILITY" in Bouvier is essential and should be consulted alongside the impossible contract entry.
A key research trap: older cases and treatises often use "impossible" to mean legally impossible (prohibited) as readily as physically impossible. Context must govern. A nineteenth-century court calling a contract "impossible of performance" may be describing illegality, destruction of subject matter, death of a necessary party, or sheer practical inability — each of which has different doctrinal consequences.
Jurisdiction matters for the modern successor doctrines. Article 2 of the UCC (applicable to goods) codifies commercial impracticability with a specific standard; common law jurisdictions apply Restatement formulations that may diverge at the margins. Neither maps perfectly onto the traditional impossible contract framework.
Researchers investigating impossibility as a defense to equitable relief — injunctions, specific performance — should note that equity courts historically applied a distinct and sometimes stricter analysis. The Remedies & Equity Encyclopedia entry cited above addresses this directly.
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Historical Dictionary Support
Bouvier's Law Dictionary defines an impossible contract as one "the law will not hold binding upon the parties because of the natural or legal impossibility of the performance by one party of that which is the consideration for the promise of the other," citing Wait's Actions and Defenses. This definition centers the analysis on the consideration — a structurally significant choice. Bouvier signals that the true category of impossible contract is narrow: if the consideration itself is impossible, no enforceable obligation arises. Mere difficulty of performance does not qualify.
Bouvier explicitly gestures at a further distinction — the entry references a distinction that is cut off in surviving text — suggesting he recognized subclasses of impossibility that the abbreviated entry fails to fully articulate. This gap is a known limitation of the source.
No other historical dictionary in the current Law Mind shelf addresses "impossible contract" as a standalone entry, though related terms (impossibility, void contract, illegal contract) receive treatment in contemporaneous sources. The absence of a fuller historical shelf on this term means Bouvier represents the primary historical anchor, and researchers should supplement it with treatise-level sources for any serious historical analysis.
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Jurisdictional Note
In the United States, the modern framework for contracts involving goods is governed by UCC § 2-615 (commercial impracticability), which applies a different standard than traditional common law impossibility. For service contracts and other non-goods agreements, common law doctrines — shaped substantially by the Restatement (Second) of Contracts §§ 261–272 — apply, with variation across jurisdictions in how strictly courts require true impossibility versus impracticability.
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Encyclopedia Cross-Reference
Contracts & Commercial Law Encyclopedia: "Discharge — Impossibility of Performance (Objective Impossibility)"
Remedies & Equity Encyclopedia: "Impossibility and Impracticability as Defenses to Equitable Relief"
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