ABSTRACT

Many defend the thesis that when someone knows p, they couldn’t easily have been wrong about p. But the notion of easy possibility in play is relatively under-theorized. One structural idea in the literature, the principle of Counterfactual Closure (CC), connects easy possibility with counterfactuals: if it easily could have happened that p, and if p were the case then q would be the case, then it follows that it easily could have happened that q. We first argue that, while CC is false, there is a true restriction of it to cases involving counterfactual dependence on a coin flip. The failure of CC falsifies a model where the easy possibilities are counterfactually similar to actuality. Next, we show that extant normality models, where the easy possibilities are the sufficiently normal ones, are incompatible with the restricted CC thesis involving coin flips. Next, we develop a new kind of normality theory that can accommodate the restricted version of CC. This new theory introduces a principle of Counterfactual Contamination, which says, roughly, that any world is fairly abnormal if at that world very abnormal events counterfactually depend on a coin flip. Finally, we explain why coin flips and other related events have a special status. A central take-home lesson is that the correct principle in the vicinity of Safety is importantly normality-theoretic rather than (as it is usually conceived) similarity-theoretic.

摘要

许多人捍卫这样一个论点，即当有人知道 p 时，他们不可能轻易地对 p 犯错。但是游戏中容易发生的可能性的概念相对缺乏理论化。文献中的一个结构性思想，即反事实封闭原则 (CC)，将简单的可能性与反事实联系起来：如果 p 很容易发生，并且如果 p 是这种情况，那么 q 就是这种情况，那么很容易q 可能会发生。我们首先争辩说，虽然 CC 是错误的，但它确实仅限于涉及反事实依赖于硬币翻转的情况。CC 的失败证明了一个模型，其中简单的可能性与现实反事实相似。接下来，我们展示了现存的正态性模型，其中简单的可能性是足够正常的，与涉及硬币翻转的受限CC论文不兼容。接下来，我们开发了一种新的常态理论，可以适应 CC 的受限版本。这个新理论引入了反事实污染原理，粗略地说，如果在那个世界上非常反常的事件反事实地依赖于硬币翻转，那么任何世界都是相当反常的。最后，我们解释了为什么抛硬币和其他相关事件具有特殊地位。一个重要的带回家的教训是，安全附近的正确原则重要的是常态理论，而不是（如通常所设想的）相似理论。如果在那个世界上非常不正常的事件反事实地依赖于硬币翻转，那么任何世界都是相当不正常的。最后，我们解释了为什么抛硬币和其他相关事件具有特殊地位。一个重要的带回家的教训是，安全附近的正确原则重要的是常态理论，而不是（如通常所设想的）相似理论。如果在那个世界上非常不正常的事件反事实地依赖于硬币翻转，那么任何世界都是相当不正常的。最后，我们解释了为什么抛硬币和其他相关事件具有特殊地位。一个重要的带回家的教训是，安全附近的正确原则重要的是常态理论，而不是（如通常所设想的）相似理论。