能力模态与析取分配原则

Ability Modals and Distribution over Disjunction

在标准的模态逻辑中,诸如“可能”“可以”等存在性模态通常遵循析取分配原则。然而,如肯尼的经典案例所示,用于表述主体能够如何行动的能力模态似乎违反析取分配原则。通常,学者们认为这一点意味着能力模态并不是存在性模态。本文将论证,在能力陈述中,通常隐含地诉诸某种成功率的概念,而对成功率的隐含化处理导致了某种辖域含混。通过在能力陈述中澄清此辖域含混淆,我们将表明肯尼式的案例并未证明能力模态违反析取分配原则。就如“可能”“可以”“也许”等典型的模态表达,能力模态依然可以被视为存在量词。至少就肯尼的案例而言,并无必要就能力概念发展独立的逻辑系统。

In standard modal logics,existential modals,such as possibility or permission,generally distribute over disjunction.Ability modals,employed to state what an agent can do,as illustrated by Kenny’s classical examples,seem to resist Distribution over Disjunction in certain cases.That is usually taken to indicate that ability modals are not really existential modals.I argue that some sort of success rate is usually implicitly referred to in ability statements,and the concealing of such success rates gives rise to a scope ambiguity.Making explicit such ambiguities will demonstrate that cases such as Kenny’s fail to show that ability modals may resist Distribution over Disjunction.Ability modals,like typical modals associated with locutions such as‘could’,‘may’and‘might’,may continue to assume their logico-semantic status as existential quantifiers,and there is no need,as far as these cases are concerned,to develop separate logics for abilities.