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根据Stalnaker的分析，存在一个最接近的世界，在这个世界里，(1)和(2)中提到的公平的硬币被抛出，硬币要么正面朝上，要么反面朝上。因此，要么（1）是真，（2）是假，要么（1）是假，（2）是真。然而，根据Lewis的分析，(1)和(2)都是假的，因为公平的硬币正面朝上的世界并不比反面朝上的世界更接近或更远离。对Lewis来说，“如果硬币被抛出，它将正面朝上或反面朝上”是真的，但这并不意味着“如果硬币被抛出，它将落在正面”，或“如果硬币被抛出，它就会反面朝上”。
根据Stalnaker的分析，存在一个最接近的世界，在这个世界里，(1)和(2)中提到的公平的硬币被抛出，硬币要么正面朝上，要么反面朝上。因此，要么（1）是真，（2）是假，要么（1）是假，（2）是真。然而，根据Lewis的分析，(1)和(2)都是假的，因为公平的硬币正面朝上的世界并不比反面朝上的世界更接近或更远离。对Lewis来说，“如果硬币被抛出，它将正面朝上或反面朝上”是真的，但这并不意味着“如果硬币被抛出，它将落在正面”，或“如果硬币被抛出，它就会反面朝上”。
=== Other accounts ===
=== 其他考虑 Other accounts ===
====因果模型 Causal models====
The ''causal models framework'' analyzes counterfactuals in terms of systems of [[structural equation model|structural equations]]. In a system of equations, each variable is assigned a value that is an explicit function of other variables in the system. Given such a model, the sentence "''Y'' would be ''y'' had ''X'' been ''x''" (formally, ''X = x'' > ''Y = y'' ) is defined as the assertion: If we replace the equation currently determining ''X'' with a constant ''X = x'', and solve the set of equations for variable ''Y'', the solution obtained will be ''Y = y''. This definition has been shown to be compatible with the axioms of possible world semantics and forms the basis for causal inference in the natural and social sciences, since each structural equation in those domains corresponds to a familiar causal mechanism that can be meaningfully reasoned about by investigators. This approach was developed by [[Judea Pearl]] (2000) as a means of encoding fine-grained intuitions about causal relations which are difficult to capture in other proposed systems.<ref name="Pearl2000">{{Cite book |last=Pearl |first=Judea |title=Causality |publisher=Cambridge University Press |year=2000 }}</ref>
The ''causal models framework'' analyzes counterfactuals in terms of systems of [[structural equation model|structural equations]]. In a system of equations, each variable is assigned a value that is an explicit function of other variables in the system. Given such a model, the sentence "''Y'' would be ''y'' had ''X'' been ''x''" (formally, ''X = x'' > ''Y = y'' ) is defined as the assertion: If we replace the equation currently determining ''X'' with a constant ''X = x'', and solve the set of equations for variable ''Y'', the solution obtained will be ''Y = y''. This definition has been shown to be compatible with the axioms of possible world semantics and forms the basis for causal inference in the natural and social sciences, since each structural equation in those domains corresponds to a familiar causal mechanism that can be meaningfully reasoned about by investigators. This approach was developed by [[Judea Pearl]] (2000) as a means of encoding fine-grained intuitions about causal relations which are difficult to capture in other proposed systems.<ref name="Pearl2000">{{Cite book |last=Pearl |first=Judea |title=Causality |publisher=Cambridge University Press |year=2000 }}</ref>
''因果模型框架''从结构方程（structural equations）系统的角度分析反事实。在一个方程系统中，每个变量都被分配了一个值，这个值是系统中其他变量的显式函数。给定这样一个模型，“如果X是X，Y就会是Y（''Y'' would be ''y'' had ''X'' been ''x''）”这个句子 (形式上为 ''X = x'' > ''Y = y'' )被定义为断言。如果我们用一个常数''X = x''取代当前决定 ''X''的方程，并求解变量''Y''的方程组，得到的解将是''Y = y''。这个定义已被证明与可能世界语义学的公理兼容，并构成自然科学和社会科学中因果推理的基础。因为这些领域的每个结构方程都对应于一个熟悉的因果机制，这个因果机制可以被研究者进行有意义地推理。这种方法是由Judea Pearl(2000)提出的，作为编码关于因果关系的细粒度直觉的手段，这些直觉在其他提议的系统中难以捕捉。<ref name="Pearl2000">{{Cite book |last=Pearl |first=Judea |title=Causality |publisher=Cambridge University Press |year=2000 }}</ref>
====信念修正 Belief revision====
====Belief revision====
In the [[belief revision]] framework, counterfactuals are treated using a formal implementation of the ''Ramsey test''. In these systems, a counterfactual ''A'' > ''B'' holds if and only if the addition of ''A'' to the current body of knowledge has ''B'' as a consequence. This condition relates counterfactual conditionals to [[belief revision]], as the evaluation of ''A'' > ''B'' can be done by first revising the current knowledge with ''A'' and then checking whether ''B'' is true in what results. Revising is easy when ''A'' is consistent with the current beliefs, but can be hard otherwise. Every semantics for belief revision can be used for evaluating conditional statements. Conversely, every method for evaluating conditionals can be seen as a way for performing revision.
In the [[belief revision]] framework, counterfactuals are treated using a formal implementation of the ''Ramsey test''. In these systems, a counterfactual ''A'' > ''B'' holds if and only if the addition of ''A'' to the current body of knowledge has ''B'' as a consequence. This condition relates counterfactual conditionals to [[belief revision]], as the evaluation of ''A'' > ''B'' can be done by first revising the current knowledge with ''A'' and then checking whether ''B'' is true in what results. Revising is easy when ''A'' is consistent with the current beliefs, but can be hard otherwise. Every semantics for belief revision can be used for evaluating conditional statements. Conversely, every method for evaluating conditionals can be seen as a way for performing revision.
在信念修正框架中，反事实是用 ''Ramsey检验''的形式化实现来处理的。在这些系统中，当且仅当在当前的知识体系添加 ''A''后得到的结果是B时，反事实''A'' > ''B''成立。这个条件将反事实条件与信念修正联系起来，因为对''A'' > ''B''的评价可以通过首先用''A''修正当前的知识，然后检查''B''在什么结果中是否为真。当''A''与当前的信念一致时，修正是很容易的，但在其他情况下可能会很难。每一个用于信念修正的语义都可以用于评价条件语句。反过来说，每一种评价条件语句的方法都可以被看作是一种执行修正的方法。
====Ginsberg====
====Ginsberg====
Ginsberg (1986) has proposed a semantics for conditionals which assumes that the current beliefs form a set of [[propositional formula]]e, considering the maximal sets of these formulae that are consistent with ''A'', and adding ''A'' to each. The rationale is that each of these maximal sets represents a possible state of belief in which ''A'' is true that is as similar as possible to the original one. The conditional statement ''A'' > ''B'' therefore holds if and only if ''B'' is true in all such sets.<ref name="rev. no. 03011">{{Citation |title=Review of the paper: M. L. Ginsberg, "Counterfactuals," Artificial Intelligence 30 (1986), pp. 35–79 |url=https://zbmath.org/?q=an:0655.03011&format=complete |work=Zentralblatt für Mathematik |pages=13–14 |year=1989 |publisher=FIZ Karlsruhe – Leibniz Institute for Information Infrastructure GmbH |zbl=0655.03011}}.</ref>
Ginsberg(1986)提出了一种条件句的语义，它假定当前的信念形成了一组命题公式，考虑这些公式中与''A''一致的最大集合，并在每个集合中加入''A''。其理由是，这些最大集合中的每一个都代表了一种可能的信念状态，在这种状态下，''A''为真，且与原始状态尽可能相似。因此，当且仅当''B''在所有这些集合中都为真时，条件陈述句''A'' > ''B''才成立。
Ginsberg (1986) has proposed a semantics for conditionals which assumes that the current beliefs form a set of [[propositional formula]]e, considering the maximal sets of these formulae that are consistent with ''A'', and adding ''A'' to each. The rationale is that each of these maximal sets represents a possible state of belief in which ''A'' is true that is as similar as possible to the original one. The conditional statement ''A'' > ''B'' therefore holds if and only if ''B'' is true in all such sets.<ref name="rev. no. 03011">{{Citation |title=Review of the paper: M. L. Ginsberg, "Counterfactuals," Artificial Intelligence 30 (1986), pp. 35–79 |url=https://zbmath.org/?q=an:0655.03011&format=complete |work=Zentralblatt für Mathematik |pages=13–14 |year=1989 |publisher=FIZ Karlsruhe – Leibniz Institute for Information Infrastructure GmbH |zbl=0655.03011}}.</ref>
== The grammar of counterfactuality ==
== The grammar of counterfactuality ==