Arguably, the proposition that Mark Twain is Samuel Clemens and the proposition that water is H2O are both a posteriori. Nevertheless, they both seem to be necessary. Ever since Davies and Humberstone (Philos Stud 38(1):1–31, 1980), it has been known that two-dimensional semantics can account for this fact. But two-dimensionalism isn’t the only theory on the market that purports to do so. In this paper, I will look at two alternatives, one by Scott Soames and one by Kathrin Gluer-Pagin and Peter Pagin, and argue that both of them fail. Regarding the former, I argue that the conceptually possible but metaphysically impossible worlds one is required to postulate are hard to conceive of on closer inspection. As for the latter, the proposal doesn’t work for certain modal sentences, and I show that it cannot be easily amended.

中文翻译：

---

一维的后验必然性

可以说，马克吐温是塞缪尔克莱门斯的命题和水是 H2O 的命题都是后验的。尽管如此，它们似乎都是必要的。自从 Davies 和 Humberstone (Philos Stud 38(1):1-31, 1980) 以来，人们就知道二维语义可以解释这个事实。但二维主义并不是市场上唯一声称这样做的理论。在本文中，我将研究两种替代方案，一种是 Scott Soames 的，另一种是 Kathrin Gluer-Pagin 和 Peter Pagin 的，并认为它们都失败了。关于前者，我认为，人们需要假设的概念上可能但形而上学上不可能的世界在仔细检查后很难想象。至于后者，该提议不适用于某些情态句，我表明它不容易修改。