In this paper, I argue that David Lewis’s possible world semantics for counterfactual discourse and for fictional discourse are apparently inconsistent and in need of revision. The problem emerges for Lewis’s account once one considers how to evaluate ambifictional counterfactuals. Since this is likely not a concept familiar to most, and since it does not appear that the problem has been previously recognized in the critical literature, I will begin by rehearsing Lewis’s possible worlds’ semantics for counterfactuals and fiction. Then I will explicate the distinction between intrafictional, extrafictional, interfictional, and ambifictional propositions. Next, I will state what an ambifictional counterfactual proposition is, and explain why this kind of discourse confounds Lewis’s system. I will conclude, finally, with a brief discussion of how the Lewisian would be best advised to resolve the paradox.

中文翻译：

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矛盾的反事实

在本文中，我认为大卫·刘易斯的反事实话语和虚构话语的可能世界语义显然是不一致的，需要修改。一旦人们考虑如何评估矛盾的反事实，刘易斯的叙述就会出现问题。由于这可能不是大多数人所熟悉的概念，并且由于批评文献中似乎没有先前认识到该问题，因此我将首先排练刘易斯的反事实和虚构的可能世界语义。然后我将解释虚构命题、虚构命题、虚构命题和矛盾命题之间的区别。接下来，我将阐述什么是矛盾的反事实命题，并解释为什么这种话语会混淆刘易斯的体系。最后，我将简要讨论如何最好地建议刘易斯主义者解决这个悖论。