反事实

"Counterfactual" redirects here. For other uses, see Counterfactual (disambiguation).

Counterfactual conditionals (also subjunctive or X-marked) are conditional sentences which discuss what would have been true under different circumstances, e.g. "If Peter believed in ghosts, he would be afraid to be here." Counterfactuals are contrasted with indicatives, which are generally restricted to discussing open possibilities. Counterfactuals are characterized grammatically by their use of fake tense morphology, which some languages use in combination with other kinds of morphology including aspect and mood.

反事实条件句（虚拟条件或X标记的）是用来讨论在不同情况下什么为真的的条件句。例如：如果彼得相信鬼魂的存在，他就会害怕来到这里。反事实句与指示句形成对比，后者一般只限于讨论开放的可能性。反事实动词的语法特征是使用虚拟时态语法，这种虚拟时态语法与时态和语态等其他语法结合使用。

Counterfactuals are one of the most studied phenomena in philosophical logic, formal semantics, and philosophy of language. They were first discussed as a problem for the material conditional analysis of conditionals, which treats them all as trivially true. Starting in the 1960s, philosophers and linguists developed the now-classic possible world approach, in which a counterfactual's truth hinges on its consequent holding at certain possible worlds where its antecedent holds. More recent formal analyses have treated them using tools such as causal models and dynamic semantics. Other research has addressed their metaphysical, psychological, and grammatical underpinnings, while applying some of the resultant insights to fields including history, marketing, and epidemiology.

反事实是哲学逻辑、形式语义学和语言哲学中研究最多的现象之一。它们首先作为条件句的实质条件分析的问题被讨论，条件句把它们都当作是微不足道的真实。从20世纪60年代开始，哲学家和语言学家发展出现在经典的可能世界方法，在这种方法中，反事实的真理取决于它在某些可能世界中的后果，而这些可能世界的前因是成立的。最近的形式化分析使用因果模型和动态语义等工具对它们进行了处理。其他研究已经解决了他们的形而上学、心理学和语法基础，同时将一些结果的见解应用到包括历史，市场营销和流行病学领域。

Overview

Examples

The difference between indicative and counterfactual conditionals can be illustrated by the following minimal pair:

指示条件句和反事实条件句之间的区别可以用下面的简单例子来说明：

1. Indicative Conditional: If it is raining right now, then Sally is inside.

1. 指示条件句： 如果现在正在下雨，那么Sally 就在里面（If it is raining right now, then Sally is inside）。

1. Simple Past Counterfactual: If it was raining right now, then Sally would be inside.

1. 一般过去时的反事实：如果现在正在下雨，那么Sally就会在里面（If it was raining right now, then Sally would be inside）。

These conditionals differ in both form and meaning. The indicative conditional uses the present tense form "is" in both the "if" clause and the "then" clause. As a result, it conveys that the speaker is agnostic about whether it is raining. The counterfactual example uses the fake tense form "was" in the "if" clause and the modal "would" in the "then" clause. As a result, it conveys that the speaker does not believe that it is raining.

这些条件句在形式和意义上都不同。指示条件在“如果(if)”和 “那么(then)”两个从句中都使用现在时态is。因此，它传达了这样一种信息：说话人对是否下雨是不可知的。反事实的例句在“如果”从句中使用虚拟时态“was”，在“ then”句中使用情态“ would”。因此，它传达的信息是，说话人并不相信天在下雨。

English has several other grammatical forms whose meanings are sometimes included under the umbrella of counterfactuality. One is the past perfect counterfactual, which contrasts with indicatives and simple past counterfactuals in its use of pluperfect morphology:

英语还有其他几种语法形式，其含义有时被包括在反事实的范畴内。其中一个是过去完成时的反事实，在使用过去完成时态时，它与指示词和一般完成时的反事实形成对比：

1. Past Perfect Counterfactual: If it had been raining yesterday, then Sally would have been inside.

1. 过去完成时的反事实：如果昨天下了雨，那么Sally就会在里面(If it had been raining yesterday, then Sally would have been inside)。

Another kind of conditional uses the form "were", generally referred to as the irrealis or subjunctive form.

Another kind of conditional uses the form "were", generally referred to as the irrealis or subjunctive form.

另一种条件句的用法是“were”，一般称为“非现实（irrealis）”或“虚拟（subjunctive）”。

1. Irrealis Counterfactual: If it were raining right now, then Sally would be inside.

1. 非现实反事实（Irrealis Counterfactual）：如果现在正在下雨，那么Sally应该在里面(If it were raining right now, then Sally would be inside)。

Past perfect and irrealis counterfactuals can undergo conditional inversion:

过去完成时和非现实的反事实可以进行条件倒置：

1. Were it raining, Sally would be inside.

1. 如果下雨的话，Sally就会在里面（Were it raining, Sally would be inside）。

1. Had it rained, Sally would be inside.

1. 那时如果下雨的话，Sally就会在里面（Had it rained, Sally would be inside）。

Terminology

<！——鉴于术语上的巨大但往往是细微的差异，本节必须经过仔细的编辑。在点击“发布更改”之前，请考虑结果文本是否有助于读者理解这些术语是如何使用的。如果结果文本读起来像是“热狗是三明治的辩论吗?”删除所有字符提示后，请不要点击”发布更改”。特别是，请确保(1)明确区分事实主张和术语定义(2)记住，不同的来源可以以不同的方式使用单一术语(3)对术语的每个术语或用法进行不偏不倚的框架性解释。-->

The term counterfactual conditional is widely used as an umbrella term for the kinds of sentences shown above. However, not all conditionals of this sort express contrary-to-fact meanings. For instance, the classic example known as the "Anderson Case" has the characteristic grammatical form of a counterfactual conditional, but does not convey that its antecedent is false or unlikely.

The term counterfactual conditional is widely used as an umbrella term for the kinds of sentences shown above. However, not all conditionals of this sort express contrary-to-fact meanings. For instance, the classic example known as the "Anderson Case" has the characteristic grammatical form of a counterfactual conditional, but does not convey that its antecedent is false or unlikely.

“反事实条件（counterfactual conditional）”这一术语被广泛用作上述各类句子的总称。然而，并非所有这类条件句都表达与事实相反的意思。例如，被称为“ Anderson 案例”的经典例子具有反事实条件的典型语法形式，但是并不表明它的先行词是假的或不可能的。

1. Anderson Case: If the patient had taken arsenic, he would have blue spots.

Anderson Case: If the patient had taken arsenic, he would have blue spots.

1. Anderson案例：如果病人服用了砒霜，他会长出蓝斑（If the patient had taken arsenic, he would have blue spots）。

Such conditionals are also widely referred to as subjunctive conditionals, though this term is likewise acknowledged as a misnomer even by those who use it. Many languages do not have a morphological subjunctive (e.g. Danish and Dutch) and many that do have it don’t use it for this sort of conditional (e.g. French, Swahili, all Indo-Aryan languages that have a subjunctive). Moreover, languages that do use the subjunctive for such conditionals only do so if they have a specific past subjunctive form. Thus, subjunctive marking is neither necessary nor sufficient for membership in this class of conditionals.

Such conditionals are also widely referred to as subjunctive conditionals, though this term is likewise acknowledged as a misnomer even by those who use it. Many languages do not have a morphological subjunctive (e.g. Danish and Dutch) and many that do have it don’t use it for this sort of conditional (e.g. French, Swahili, all Indo-Aryan languages that have a subjunctive). Moreover, languages that do use the subjunctive for such conditionals only do so if they have a specific past subjunctive form. Thus, subjunctive marking is neither necessary nor sufficient for membership in this class of conditionals.

这种条件句也被广泛地称为虚拟条件句（subjunctive conditionals），尽管这个术语同样被使用者认为是用词不当。许多语言都没有虚拟语气（如丹麦语和荷兰语)，许多有从句的语言也不把它用于这种条件句（如法语、斯瓦希里语、所有有从句的印度-雅利安语）。此外，只有将虚拟语气用于此类条件的语言才具有特定的过去虚拟语气形式。因此，虚拟标记既不是必要的，也不是充分的。

The terms counterfactual and subjunctive have sometimes been repurposed for more specific uses. For instance, the term "counterfactual" is sometimes applied to conditionals that express a contrary-to-fact meaning, regardless of their grammatical structure. Along similar lines, the term "subjunctive" is sometimes used to refer to conditionals that bear fake past or irrealis marking, regardless of the meaning they convey.

Recently the term X-Marked has been proposed as a replacement, evoking the extra marking that these conditionals bear. Those adopting this terminology refer to indicative conditionals as O-Marked conditionals, reflecting their ordinary marking.

反事实（counterfactual） and 从句（subjunctive）这两个术语有时被重新用于更具体的用途。例如，不管其语法结构如何，"反事实"这个术语有时被用于表达与事实相反的意思的条件语。按照类似的思路，不管其表达的意思如何，"从句"这个术语有时被用于指带有虚拟过去或非现实标记的条件语。

最近有人提出用术语 X-Marked这个词来替代，以概括这些条件语所带有的额外标记。采用这个术语的人把指示性条件语称为O-Marked条件语，反映了它们的普通标记。

Recently the term X-Marked has been proposed as a replacement, evoking the extra marking that these conditionals bear. Those adopting this terminology refer to indicative conditionals as O-Marked conditionals, reflecting their ordinary marking.

The antecedent of a conditional is sometimes referred to as its "if"-clause or protasis. The consequent of a conditional is sometimes referred to as a "then"-clause or as an apodosis.

一个条件的 前件（antecedent）有时被称为 "如果"从句或条件子句。条件的结果有时被称为"那么"子句或结论子句。

Logic and semantics

According to the material conditional analysis, a natural language conditional, a statement of the form ‘if P then Q’, is true whenever its antecedent, P, is false. Since counterfactual conditionals are those whose antecedents are false, this analysis would wrongly predict that all counterfactuals are vacuously true. Goodman illustrates this point using the following pair in a context where it is understood that the piece of butter under discussion had not been heated.

根据实质条件的分析，自然语言条件句---- 形式为如果 p 那么 q 的陈述---- 只要其先行词 p 为假就是真。由于反事实条件句是那些前置假设的条件句，这种分析会错误地预测所有反事实条件句都是真空的。古德曼用下面的一对来说明这一点，在这个背景下，我们知道正在讨论的那块黄油并没有被加热。

If that piece of butter had been heated to 150º, it would have melted.

如果那块黄油被加热到150度，它就会融化。

Counterfactuals were first discussed by Nelson Goodman as a problem for the material conditional used in classical logic. Because of these problems, early work such as that of W.V. Quine held that counterfactuals aren't strictly logical, and do not make true or false claims about the world. However, in the 1970s, David Lewis showed that these problems are surmountable given an appropriate logical framework. Work since then in formal semantics, philosophical logic, philosophy of language, and cognitive science has built on Lewis's insight, taking it in a variety of different directions.

If that piece of butter had been heated to 150º, it would not have melted.

如果那块黄油被加热到150度，它就不会融化。

Classic puzzles

More generally, such examples show that counterfactuals are not truth-functional. In other words, knowing whether the antecedent and consequent are actually true is not sufficient to determine whether the counterfactual itself is true.

更一般地说，这些例子表明反事实并不是真理功能的。换句话说，知道先行词和结果是否真实并不足以确定反事实本身是否真实。

The problem of counterfactuals

If Caesar had been in command in Korea, he would have used the atom bomb.

如果凯撒当时在朝鲜指挥，他会使用原子弹。

If Caesar had been in command in Korea, he would have used catapults.

如果凯撒在朝鲜指挥，他会使用投石器。

According to the material conditional analysis, a natural language conditional, a statement of the form ‘if P then Q’, is true whenever its antecedent, P, is false. Since counterfactual conditionals are those whose antecedents are false, this analysis would wrongly predict that all counterfactuals are vacuously true. Goodman illustrates this point using the following pair in a context where it is understood that the piece of butter under discussion had not been heated.

1. If that piece of butter had been heated to 150º, it would have melted.

1. If that piece of butter had been heated to 150º, it would not have melted.

Counterfactuals are non-monotonic in the sense that their truth values can be changed by adding extra material to their antecedents. This fact is illustrated by Sobel sequences such as the following:

反事实是非单调的，因为它们的真值可以通过在其先行词中添加额外的材料而改变。这一事实可以通过 Sobel 序列得到说明，例如:

More generally, such examples show that counterfactuals are not truth-functional. In other words, knowing whether the antecedent and consequent are actually true is not sufficient to determine whether the counterfactual itself is true.

If Hannah had drunk coffee, she would be happy.

如果汉娜喝了咖啡，她会很高兴的。

Context dependence and vagueness

If Hannah had drunk coffee and the coffee had gasoline in it, she would be sad.

如果汉娜喝了咖啡，咖啡里加了汽油，她会伤心的。

If Hannah had drunk coffee and the coffee had gasoline in it and Hannah was a gasoline-drinking robot, she would be happy.

如果汉娜喝了咖啡，咖啡里加了汽油，而汉娜是个喝汽油的机器人，她会很高兴的。

Counterfactuals are context dependent and vague. For example, either of the following statements can be reasonably held true, though not at the same time:

One way of formalizing this fact is to say that the principle of Antecedent Strengthening should not hold for any connective > intended as a formalization of natural language conditionals.

形式化这一事实的一种方法是说，先行强化原则不适用于任何连接词，它是自然语言条件句的形式化。

1. If Caesar had been in command in Korea, he would have used the atom bomb.

1. If Caesar had been in command in Korea, he would have used catapults.

Non-monotonicity

Counterfactuals are non-monotonic in the sense that their truth values can be changed by adding extra material to their antecedents. This fact is illustrated by Sobel sequences such as the following:

The most common logical accounts of counterfactuals are couched in the possible world semantics. Broadly speaking, these approaches have in common that they treat a counterfactual A > B as true if B holds across some set of possible worlds where A is true. They vary mainly in how they identify the set of relevant A-worlds.

反事实的最常见的逻辑解释是可能世界语义学。一般来说，这些方法的共同点是，如果 b 持有一些可能的世界集合，其中 a 是真实的，那么它们就把反事实的 a > b 当作真实的。它们主要在如何识别相关的 a 世界集方面有所不同。

1. If Hannah had drunk coffee, she would be happy.

David Lewis's variably strict conditional is considered the classic analysis within philosophy. The closely related premise semantics proposed by Angelika Kratzer is often taken as the standard within linguistics. However, there are numerous possible worlds approaches on the market, including dynamic variants of the strict conditional analysis originally dismissed by Lewis.

大卫 · 刘易斯多变的严格条件被认为是哲学中的经典分析。安吉利卡 · 克拉策提出的前提语义学是语言学中的一个标准。然而，市场上有许多可能的世界方法，包括最初被 Lewis 摒弃的严格条件分析的动态变体。

1. If Hannah had drunk coffee and the coffee had gasoline in it, she would be sad.

1. If Hannah had drunk coffee and the coffee had gasoline in it and Hannah was a gasoline-drinking robot, she would be happy.

One way of formalizing this fact is to say that the principle of Antecedent Strengthening should not hold for any connective > intended as a formalization of natural language conditionals.

The strict conditional analysis treats natural language counterfactuals as being equivalent to the modal logic formula [math]\displaystyle{ \Box(P \rightarrow Q) }[/math]. In this formula, [math]\displaystyle{ \Box }[/math] expresses necessity and [math]\displaystyle{ \rightarrow }[/math] is understood as material implication. This approach was first proposed in 1912 by C.I. Lewis as part of his axiomatic approach to modal logic.

严格条件分析将自然语言反事实视为等同于模态逻辑公式。在这个公式中，Box 表示必要性，right tarrow </math > 被理解为实质条件。这种方法最早是在1912年由 c.i. 提出的。刘易斯的公理化方法的一部分，模态逻辑。

• Antecedent Strengthening: [math]\displaystyle{ P \gt Q \models (P \land R) \gt Q }[/math]

Possible worlds accounts

The most common logical accounts of counterfactuals are couched in the possible world semantics. Broadly speaking, these approaches have in common that they treat a counterfactual A > B as true if B holds across some set of possible worlds where A is true. They vary mainly in how they identify the set of relevant A-worlds.

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，我们使用 Ramsey 测试的一个正式实现来处理反事实问题。在这些系统中，一个反事实的 a > b 成立当且仅当 a 加入到当前的知识体系中的结果是 b。这个条件将反事实条件与信念修正联系起来，因为 a > b 的评估可以通过首先用 a 修正当前的知识，然后检查 b 在什么结果中是否为真来完成。当 a 与当前的信念一致时，复习就容易了，否则就很难了。每个信念修正的语义都可以用于条件语句的求值。反过来，每一种条件求值方法都可以看作是一种执行修正的方法。

David Lewis's variably strict conditional is considered the classic analysis within philosophy. The closely related premise semantics proposed by Angelika Kratzer is often taken as the standard within linguistics. However, there are numerous possible worlds approaches on the market, including dynamic variants of the strict conditional analysis originally dismissed by Lewis.

Strict conditional

Ginsberg (1986) has proposed a semantics for conditionals which assumes that the current beliefs form a set of propositional formulae, 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.

Ginsberg (1986)提出了条件句的语义假设，假设当前的信念构成一组命题公式，考虑这些公式的最大集与 a 相一致，并在每个公式中加入 a。其基本原理是，这些最大集合中的每一个都代表了一种可能的信念状态，其中 a 为真，且尽可能与原始信念相似。因此，If判断语句集 a > b 成立的充要条件是 b 在所有这样的集合中都为真。

The strict conditional analysis treats natural language counterfactuals as being equivalent to the modal logic formula [math]\displaystyle{ \Box(P \rightarrow Q) }[/math]. In this formula, [math]\displaystyle{ \Box }[/math] expresses necessity and [math]\displaystyle{ \rightarrow }[/math] is understood as material implication. This approach was first proposed in 1912 by C.I. Lewis as part of his axiomatic approach to modal logic. In modern relational semantics, this means that the strict conditional is true at w iff the corresponding material conditional is true throughout the worlds accessible from w. More formally:

• Given a model [math]\displaystyle{ M = \langle W,R,V \rangle }[/math], we have that [math]\displaystyle{ M,w \models \Box(P \rightarrow Q) }[/math] iff [math]\displaystyle{ M, v \models P \rightarrow Q }[/math] for all [math]\displaystyle{ v }[/math] such that [math]\displaystyle{ Rwv }[/math]

Languages use different strategies for expressing counterfactuality. Some have a dedicated counterfactual morphemes, while others recruit morphemes which otherwise express tense, aspect, mood, or a combination thereof. Since the early 2000s, linguists, philosophers of language, and philosophical logicians have intensely studied the nature of this grammatical marking, and it continues to be an active area of study.

语言使用不同的策略来表达反事实。一些语素有专门的反事实语素，而另一些语素则表示时态、方面、语气或者它们的组合。自2000年代初以来，语言学家、语言哲学家和哲学逻辑学家对这种语法标记的本质进行了大量的研究，并且一直是一个活跃的研究领域。

Unlike the material conditional, the strict conditional is not vacuously true when its antecedent is false. To see why, observe that both [math]\displaystyle{ P }[/math] and [math]\displaystyle{ \Box(P \rightarrow Q) }[/math] will be false at [math]\displaystyle{ w }[/math] if there is some accessible world [math]\displaystyle{ v }[/math] where [math]\displaystyle{ P }[/math] is true and [math]\displaystyle{ Q }[/math] is not. The strict conditional is also context-dependent, at least when given a relational semantics (or something similar). In the relational framework, accessibility relations are parameters of evaluation which encode the range of possibilities which are treated as "live" in the context. Since the truth of a strict conditional can depend on the accessibility relation used to evaluate it, this feature of the strict conditional can be used to capture context-dependence.

The strict conditional analysis encounters many known problems, notably monotonicity. In the classical relational framework, when using a standard notion of entailment, the strict conditional is monotonic, i.e. it validates Antecedent Strengthening. To see why, observe that if [math]\displaystyle{ P \rightarrow Q }[/math] holds at every world accessible from [math]\displaystyle{ w }[/math], the monotonicity of the material conditional guarantees that [math]\displaystyle{ P \land R \rightarrow Q }[/math] will be too. Thus, we will have that [math]\displaystyle{ \Box(P \rightarrow Q) \models \Box(P \land R \rightarrow Q) }[/math].

This fact led to widespread abandonment of the strict conditional, in particular in favor of Lewis's variably strict analysis. However, subsequent work has revived the strict conditional analysis by appealing to context sensitivity. This approach was pioneered by Warmbrōd (1981), who argued that Sobel sequences don't demand a non-monotonic logic, but in fact can rather be explained by speakers switching to more permissive accessibility relations as the sequence proceeds. In his system, a counterfactual like "If Hannah had drunk coffee, she would be happy" would normally be evaluated using a model where Hannah's coffee is gasoline-free in all accessible worlds. If this same model were used to evaluate a subsequent utterance of "If Hannah had drunk coffee and the coffee had gasoline in it...", this second conditional would come out as trivially true, since there are no accessible worlds where its antecedent holds. Warmbrōd's idea was that speakers will switch to a model with a more permissive accessibility relation in order to avoid this triviality.

In many languages, counterfactuality is marked by past tense morphology. Since these uses of the past tense do not convey their typical temporal meaning, they are called fake past or fake tense. English is one language which uses fake past to mark counterfactuality, as shown in the following minimal pair. In the indicative example, the bolded words are present tense forms. In the counterfactual example, both words take their past tense form. This use of the past tense cannot have its ordinary temporal meaning, since it can be used with the adverb "tomorrow" without creating a contradiction.

在许多语言中，反事实性以过去时态形态学为标志。由于过去时的这些用法没有传达其典型的时间意义，所以它们被称为假过去时或假过去时。英语是一种使用虚假过去来标记反事实性的语言，如下面的最小对所示。在陈述句中，粗体词是现在时态的形式。在反事实的例子中，两个词都采用过去时态。过去时的这种用法不可能有普通的时间意义，因为它可以和副词“明天”一起使用，而不会产生矛盾。

Subsequent work by Kai von Fintel (2001), Thony Gillies (2007), and Malte Willer (2019) has formalized this idea in the framework of dynamic semantics, and given a number of linguistic arguments in favor. One argument is that conditional antecedents license negative polarity items, which are thought to be licensed only by monotonic operators.

Indicative: If Natalia leaves tomorrow, she will arrive on time.

如果娜塔莉亚明天离开，她会准时到达。

1. If Hannah had drunk any coffee, she would be happy.

Counterfactual: If Natalia left tomorrow, she would arrive on time.

反事实: 如果娜塔莉亚明天离开，她会准时到达。

Another argument in favor of the strict conditional comes from Irene Heim's observation that Sobel Sequences are generally infelicitous (i.e. sound strange) in reverse.

Modern Hebrew is another language where counterfactuality is marked with a fake past morpheme:

现代希伯来语是另一种用假的过去语素标记反事实性的语言:

1. If Hannah had drunk coffee with gasoline in it, she would not be happy. But if she had drunk coffee, she would be happy.

im

Dani

haya

ba-bayit

maχa ɾ

hayinu

mevakRim

oto

im

Dani

haya

ba-bayit

maχa ɾ

hayinu

mevakRim

oto Sarah Moss (2012) and Karen Lewis (2018) have responded to these arguments, showing that a version of the variably strict analysis can account for these patterns, and arguing that such an account is preferable since it can also account for apparent exceptions. As of 2020, this debate continues in the literature, with accounts such as Willer (2019) arguing that a strict conditional account can cover these exceptions as well.

if

Dani

be.pst.3sm

in-home

tomorrow

be.pst.1pl

visit.ptc.pl

he.acc 如果达尼在家里，明天，在家里，在家里，在家里，在家里 Variably strict conditional

'If Dani had been home tomorrow, we would’ve visited him.'

如果丹妮明天在家，我们就会去看他了

In the variably strict approach, the semantics of a conditional A > B is given by some function on the relative closeness of worlds where A is true and B is true, on the one hand, and worlds where A is true but B is not, on the other.

Palestinian Arabic is another:

巴勒斯坦阿拉伯语是另一个例子:

On Lewis's account, A > C is (a) vacuously true if and only if there are no worlds where A is true (for example, if A is logically or metaphysically impossible); (b) non-vacuously true if and only if, among the worlds where A is true, some worlds where C is true are closer to the actual world than any world where C is not true; or (c) false otherwise. Although in Lewis's Counterfactuals it was unclear what he meant by 'closeness', in later writings, Lewis made it clear that he did not intend the metric of 'closeness' to be simply our ordinary notion of overall similarity.

Example:

In formal semantics and philosophical logic, fake past is regarded as a puzzle, since it is not obvious why so many unrelated languages would repurpose a tense morpheme to mark counterfactuality. Proposed solutions to this puzzle divide into two camps: past as modal and past as past. These approaches differ in whether or not they take the past tense's core meaning to be about time.

在形式语义学和哲学逻辑中，虚假的过去被认为是一个谜，因为不明显的是为什么这么多不相关的语言重新使用一个时态语素来标记反事实性。针对这一难题提出的解决办法分为两个阵营: 过去为模式和过去为过去。这些方法的不同之处在于它们是否将过去时的核心意思理解为与时间有关。

If he had eaten more at breakfast, he would not have been hungry at 11 am.

On Lewis's account, the truth of this statement consists in the fact that, among possible worlds where he ate more for breakfast, there is at least one world where he is not hungry at 11 am and which is closer to our world than any world where he ate more for breakfast but is still hungry at 11 am.

In the past as modal approach, the denotation of the past tense is not fundamentally about time. Rather, it is an underspecified skeleton which can apply either to modal or temporal content. For instance, the particular past as modal proposal of Iatridou (2000), the past tense's core meaning is what's shown schematically below:

过去式作为情态动词的方法，过去时的外延从根本上说不是关于时间的。相反，它是一个未指定的框架，既可以应用于模态内容，也可以应用于时态内容。例如，Iatridou (2000)的特殊过去式作为情态提议，过去式的核心含义是下面的图示:

Stalnaker's account differs from Lewis's most notably in his acceptance of the limit and uniqueness assumptions. The uniqueness assumption is the thesis that, for any antecedent A, among the possible worlds where A is true, there is a single (unique) one that is closest to the actual world. The limit assumption is the thesis that, for a given antecedent A, if there is a chain of possible worlds where A is true, each closer to the actual world than its predecessor, then the chain has a limit: a possible world where A is true that is closer to the actual worlds than all worlds in the chain. (The uniqueness assumption entails the limit assumption, but the limit assumption does not entail the uniqueness assumption.) On Stalnaker's account, A > C is non-vacuously true if and only if, at the closest world where A is true, C is true. So, the above example is true just in case at the single, closest world where he ate more breakfast, he does not feel hungry at 11 am. Although it is controversial, Lewis rejected the limit assumption (and therefore the uniqueness assumption) because it rules out the possibility that there might be worlds that get closer and closer to the actual world without limit. For example, there might be an infinite series of worlds, each with a coffee cup a smaller fraction of an inch to the left of its actual position, but none of which is uniquely the closest. (See Lewis 1973: 20.)

The topic x is not the contextually-provided x

主题 x 不是上下文提供的 x

One consequence of Stalnaker's acceptance of the uniqueness assumption is that, if the law of excluded middle is true, then all instances of the formula (A > C) ∨ (A > ¬C) are true. The law of excluded middle is the thesis that for all propositions p, p ∨ ¬p is true. If the uniqueness assumption is true, then for every antecedent A, there is a uniquely closest world where A is true. If the law of excluded middle is true, any consequent C is either true or false at that world where A is true. So for every counterfactual A > C, either A > C or A > ¬C is true. This is called conditional excluded middle (CEM). Example:

Depending on how this denotation composes, x can be a time interval or a possible world. When x is a time, the past tense will convey that the sentence is talking about non-current times, i.e. the past. When x is a world, it will convey that the sentence is talking about a potentially non-actual possibility. The latter is what allows for a counterfactual meaning.

根据这个指称的组成，x 可以是时间间隔，也可以是可能世界。当 x 是时间时，过去时态表示句子指的是非现在时间，也就是说，过去时态指的是非现在时间。过去。当 x 是一个世界时，它将传达出这个句子所指的是一种潜在的不真实的可能性。后者是允许反事实意义的东西。

(1) If the fair coin had been flipped, it would have landed heads.

The past as past approach treats the past tense as having an inherently temporal denotation. On this approach, so-called fake tense isn't actually fake. It differs from "real" tense only in how it takes scope, i.e. which component of the sentence's meaning is shifted to an earlier time. When a sentence has "real" past marking, it discusses something that happened at an earlier time; when a sentence has so-called fake past marking, it discusses possibilities that were accessible at an earlier time but may no longer be.

过去时作为过去时的方法认为过去时具有内在的时间外延。在这种方法中，所谓的假时态实际上并不是假的。它与“真实”时态的区别仅在于它如何占据范围，即。句子的哪个部分的意思转移到了更早的时间。当一个句子有“真实的”过去标记时，它讨论的是发生在更早的时间的事情; 当一个句子有所谓的“假过去标记”时，它讨论的可能性在更早的时间是可以接受的，但可能不再是。

(2) If the fair coin had been flipped, it would have landed tails (i.e. not heads).

On Stalnaker's analysis, there is a closest world where the fair coin mentioned in (1) and (2) is flipped and at that world either it lands heads or it lands tails. So either (1) is true and (2) is false or (1) is false and (2) true. On Lewis's analysis, however, both (1) and (2) are false, for the worlds where the fair coin lands heads are no more or less close than the worlds where they land tails. For Lewis, "If the coin had been flipped, it would have landed heads or tails" is true, but this does not entail that "If the coin had been flipped, it would have landed heads, or: If the coin had been flipped it would have landed tails."

Other accounts

Fake aspect often accompanies fake tense in languages that mark aspect. In some languages (e.g. Modern Greek, Zulu, and the Romance languages) this fake aspect is imperfective. In other languages (e.g. Palestinian Arabic) it is perfective. However, in other languages including Russian and Polish, counterfactuals can have either perfective or imperfective aspect. In other experiments, participants were asked to read short stories that contained counterfactual conditionals, e.g., ‘If there had been roses in the flower shop then there would have been lilies’. Later in the story, they read sentences corresponding to the presupposed facts, e.g., ‘there were no roses and there were no lilies’. The counterfactual conditional primed them to read the sentence corresponding to the presupposed facts very rapidly; no such priming effect occurred for indicative conditionals. They spent different amounts of time 'updating' a story that contains a counterfactual conditional compared to one that contains factual information and focused on different parts of counterfactual conditionals.

在标记体的语言中，假体往往伴随着假时态。在某些语言中(例如:。现代希腊语、祖鲁语和罗曼语)这个虚构的部分是不完整的。用其他语言(例如:。巴勒斯坦阿拉伯语)这是完美的。然而，在包括俄语和波兰语在内的其他语言中，反事实可以是完成体或非完整体。在其他实验中，参与者被要求阅读包含反事实条件的短篇小说，例如，如果花店里有玫瑰，那么就会有百合花。在故事的后半部分，他们阅读与预设事实相对应的句子，例如，没有玫瑰，也没有百合。反事实条件让他们非常快速地阅读与预设事实相对应的句子; 指示性条件句则没有这样的启动效应。他们花了不同数量的时间更新一个包含反事实条件的故事，而不是一个包含事实信息的故事，并且关注不同部分的反事实条件句。

Causal models

Experiments have compared the inferences people make from counterfactual conditionals and indicative conditionals. Given a counterfactual conditional, e.g., 'If there had been a circle on the blackboard then there would have been a triangle', and the subsequent information 'in fact there was no triangle', participants make the modus tollens inference 'there was no circle' more often than they do from an indicative conditional. Given the counterfactual conditional and the subsequent information 'in fact there was a circle', participants make the modus ponens inference as often as they do from an indicative conditional. See counterfactual thinking.

实验比较了人们从反事实条件句和指示性条件句中得出的推论。给定一个反事实条件，例如，如果黑板上有一个圆，那么就会有一个三角形，并且随后的信息事实上没有三角形，参与者做这种推断的频率比他们从一个直陈条件推断的频率更高。考虑到反事实条件和随后的信息‘事实上存在一个循环’，参与者做这种推理的频率和他们从直陈条件推理的频率一样高。参见反事实思维。

Byrne argues that people construct mental representations that encompass two possibilities when they understand, and reason from, a counterfactual conditional, e.g., 'if Oswald had not shot Kennedy, then someone else would have'. They envisage the conjecture 'Oswald did not shoot Kennedy and someone else did' and they also think about the presupposed facts 'Oswald did shoot Kennedy and someone else did not'. According to the mental model theory of reasoning, they construct mental models of the alternative possibilities.

认为人们构建的心理表征包括两种可能性，一种是他们理解的反事实条件，另一种是推理，例如，如果 Oswald 没有射杀 Kennedy，那么其他人也会射杀 Kennedy。他们猜想肯尼迪不是奥斯瓦尔德杀的，而是别人杀的，他们还想到了预先假定的事实奥斯瓦尔德确实杀了肯尼迪，而别人没有。根据心理模型推理理论，他们构建了可选择可能性的心理模型。

The causal models framework analyzes counterfactuals in terms of systems of 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.

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.

Ginsberg

Ginsberg (1986) has proposed a semantics for conditionals which assumes that the current beliefs form a set of propositional formulae, 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.

The grammar of counterfactuality

Languages use different strategies for expressing counterfactuality. Some have a dedicated counterfactual morphemes, while others recruit morphemes which otherwise express tense, aspect, mood, or a combination thereof. Since the early 2000s, linguists, philosophers of language, and philosophical logicians have intensely studied the nature of this grammatical marking, and it continues to be an active area of study.

Fake tense

Description

In many languages, counterfactuality is marked by past tense morphology. Since these uses of the past tense do not convey their typical temporal meaning, they are called fake past or fake tense. English is one language which uses fake past to mark counterfactuality, as shown in the following minimal pair. In the indicative example, the bolded words are present tense forms. In the counterfactual example, both words take their past tense form. This use of the past tense cannot have its ordinary temporal meaning, since it can be used with the adverb "tomorrow" without creating a contradiction.

1. Indicative: If Natalia leaves tomorrow, she will arrive on time.

1. Counterfactual: If Natalia left tomorrow, she would arrive on time.

Modern Hebrew is another language where counterfactuality is marked with a fake past morpheme:

Category:Conditionals in linguistics

范畴: 语言学中的条件句

Category:Grammar 分类: 语法 Category:Belief revision 类别: 信念修正

	im	Dani	haya	ba-bayit	maχa ɾ	hayinu	mevakRim	oto Category:Semantics 分类: 语义学
	if	Dani	be.pst.3sm	in-home	tomorrow	be.pst.1pl	visit.ptc.pl	he.acc Category:Thought experiments 类别: 思维实验

'If Dani had been home tomorrow, we would’ve visited him.'

Category:Linguistic modality

类别: 情态

This page was moved from wikipedia:en:Counterfactual conditional. Its edit history can be viewed at 反事实/edithistory