Taylor v Caldwell Context <Back>
For the purpose of automatically generating arguments, argumentation modules are represented by assumption-based argumentation frameworks, which are triples (R,A,Con) consisting of a set R of inference rules, a set A of assumptions, and a contrary function Con mapping assumptions of A to sentences (of the underlying language), as follows.
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BO=BE=(R,A,Con) with R consists of the following rule:
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• ¬HallExist ← Fire
stating that the hall is destroyed by the fire.
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• ¬RentHall ← ¬HallExist
stating that it is impossible to rent the hall without its existence.
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• and A = {HallExist}, Con(HallExist) = ¬HallExist
intuitively says that the hall is commonly assumed to exist, unless there is explicit evidence to the contrary. The absence of rules concluding Fire represents that neither parties believed in any dangers of fire.
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KO = KE = BO = BE representing that both parties are not expected to know that the fire could happen.
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CK is divided into the temporal common knowledge CKt and the general domain common knowledge CKd
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CKt =(Rt,At,Con) with At = ∅ and Rt = {E ⊏ Fire ←} stating that Fire occurred after the contract-making event E.
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CKd = BO = BE.
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Cost function is undefined, representing that neither parties do anything to prevent the fire or mitigate its consequences.
From these module the following arguments about factors of the case can be made:
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✓Fire happened after contract making as CKt ⊢sk E ⊏ Fire.
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✓Fire is unexpected for both parties as there are no arguments supporting Fire from both BO and BE.
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✓Fire destroys HallExist as CKd ∪ {Fire} ⊢sk ¬HallExist.
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✓RentHall is impossible without HallExist as:
CKd ∪ {¬HallExist} ⊢sk ¬RentHall.
Let IMPOS be a module representing the doctrine of impossibility (as graphically presented in this page and formally presented in this article), it is easy to see that conditions 1 and 2 of the doctrine hold since
IMPOS ⊢sk Impossibility(contract).
Further, conditions 3 and 4 also hold since there are no arguments for RiskAllocatedTo(Caldwell, contract).
Thus MoDiSo will say that IMPOS ⊢sk Rescind(Caldwell, contract), i.e. Caldwell could rescind from performing the contract on the grounds of impossibility.