This article sits at a point of intersection between the philosophy of physics and the metaphysics of modality. There are clear similarities between Everettian quantum mechanics and various modal metaphysical theories, but there have hitherto been few attempts at exploring how the two topics relate. In this article, I build on a series of recent papers by Wilson ([2011], [2012], [2013]), who argues that Everettian quantum mechanics’ connections with traditional modal metaphysics are vital in defending it against objections. I show that Wilson’s preferred version of Everettian quantum mechanics has two problems. First, it is unable to account for the contingency of various intuitively contingent modal claims. Second, it fails to yield intuitive truth values on modal claims about the number of branches in a given Everettian multiverse. Since modal claims about branch number are instrumental in decision-theoretic solutions to Everettian quantum mechanics’ problem(s) with probability, this second problem has wider dialectical implications. I suggest amendments to the underlying metaphysics that overcome these problems. The result is a more robust version of Everettian quantum mechanics.

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埃弗里特量子力学和模态的形而上学

这篇文章位于物理学哲学和模态形而上学之间的交叉点。埃弗里特量子力学和各种模态形而上学理论之间有明显的相似之处，但迄今为止，很少有人尝试探索这两个主题之间的关系。在本文中，我以 Wilson（[2011]、[2012]、[2013]）最近的一系列论文为基础，他们认为埃弗雷特量子力学与传统模态形而上学的联系对于捍卫它免受反对意见至关重要。我表明威尔逊偏爱的埃弗里特量子力学版本有两个问题。首先，它无法解释各种直觉上或有模态声明的偶然性。其次，它无法产生关于给定 Everett 多元宇宙中分支数量的模态声明的直观真值。由于关于分支数的模态声明有助于埃弗里特量子力学概率问题的决策理论解决方案，因此第二个问题具有更广泛的辩证意义。我建议对克服这些问题的基本形而上学进行修正。结果是更强大的埃弗里特量子力学版本。