Moral obligation and permissibility are usually thought to be interdefinable. Following the pattern of the duality definitions of necessity and possibility, we have that something's being permissible could be defined as its not being obligatory to not do it. And that something's being obligatory could be defined as its not being permissible to not do it. In this paper, I argue that neither direction of this alleged interdefinability works. Roughly, the problem is that a claim that some act is obligatory or permissible entails that there is a moral law, whereas a negative claim that some act is not obligatory or not permissible does not. Nevertheless, one direction of the interdefinability can potentially be salvaged. I argue that, if we do not require the conceptual possibility of moral dilemmas, then there is a way to plausibly define obligation in terms of permissibility. I conclude that permissibility is the only feasible deontic primitive.

中文翻译：

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许可是唯一可行的道义原始语

人们通常认为道德义务和可容许性是可界定的。遵循必然性和可能性的二重性定义的模式，我们认为可以将某些东西定义为不需要强制执行某项操作。这事的是强制性可被定义为它的不被容许不这样做。在本文中，我认为这种所谓的可互定义性的任何方向都行不通。大致而言，问题在于，声称某些行为是强制性的或可允许的，这就意味着存在道德法则，而否定性的声称某些行为不是强制性的或不被允许的则不是这样。然而，可互解性的一个方向可能会得到挽救。我认为，如果我们不需要道德困境的概念可能性，那么就有一种方法可以根据可允许性合理地定义义务。我得出结论，许可性是唯一可行的道义论原语。