条件句ConditionalS

条件句逻辑与汉语条件句的解释

条件句逻辑与汉语条件句的解释 条件命题 P → Q 前件：antecedent 后件：consequent 条件连词：→（箭头） →真值表 Conditional (where P is the antecedent and Q, the consequent; or P is the protasis and Q, the apodosis): P→Q 111 100 011 010 Modus Ponendo Ponens (MPP) 肯定前件律 A,A→B┝B Modus Tollendo Tollens (MTT) 否定后件律 ~B, A→B┝~A (1)P → Q (2)~Q → ~P （contraposition 质位互换）

充分条件同（1） 必要条件： （3）Q → P 对（3）作质位互换，得（4） （4）~P → ~Q （同（3）的必要条件关系） 举例： （5）So long as we scatter it, thought force is of little use to us, but as soon as we are prepared to take the trouble necessary to harness it, all knowledge is ours. （6）只要使用这种洗涤剂，便可洗得干干净净。 (7) 只要把球传给队友，他们就能得分。 (8) 只要你脸蛋长得还算过得去，哪怕一个字也不认识，也照样能当演 员。 以上充分条件句 （9）Nothing terrible will befall if you eat a piece of pizza — only if you exist on a diet of nothing but pizza. (10) We all agree that small stores are important, but they can remain viable only if they can carry out their trading on Sundays.

指示条件句

指示條件句 指示條件句(indicative conditionals)是條件句的一種，其與虛擬條件句(subjunctive conditionals)在英文裡都具有”If…then…”這樣的句型，而它們之間的差別則在於動詞的語氣（mood）上。指示條件句與虛擬條件句在動詞語氣上的不同，並不意味著兩者非得有不同的語意論(semantics)不可。有些哲學家，如M. Woods和R. Stalnaker，便認為這兩者的差異其實是在語用(pragmatics)而非在語意上，但也有一些哲學家，如D. Lewis和F. Jackson，則認為它們是兩種在語意上截然不同的條件句。我這次演講的焦點集中在指示條件句的語意論以及這兩種條件句的關聯之上。 指示條件句的語意論自古以來即有爭議；有關指示條件句語意上的爭論至少可以追溯至斯多葛(Stoics)時期。根據Sextus Empiricus的說法，斯多葛學派中就有四種關於指示條件句語意論的看法：(1) Philo認為指示條件句中的”If…then…”為真值函數的連接詞；”If P then Q”在前件真而後件假時為假，在其他的情形下則為真。(2) Philo的老師Diodorus則認為指示條件句所表達的是涉及時的全稱性命題；”If P then Q”為真的條件是：在過去、現在和未來中，沒有任何時間裡P為真而Q卻為假。(3) Chrysippus認為”If…then…”為非真值函數的連接詞；”If P then Q”這樣的條件句表達了某種其前件與後件間在容貫性上的關聯：”If P then Q”為真若且惟若肯定其前件而否定其後件會導致不一致。(4) 最後，當時還有一些哲學家(已無法考據是誰)反對前述三種看法，他們認為，”If P then Q”這樣的條件句為真若且惟若Q在實質上「被包含在」(included)前件中。 對於這四種看法，我們可以用當代的邏輯符號來加以重新表述如下：(1) Philo認為”If P then Q”的意思就是”P ?Q”，其中”?”代表實質蘊含(material implication)；(2) Diodorus認為”If P then Q”的意思是”(t)(P is true-at-t ? Q is true-at-t)”，其中”t”是時間變數；(3) Chrysippus認為”If P then Q”的意思是”□(P ?Q)”，其中”□”代表「必然地」這個模態詞；(4)至於其他主張「包含」關係的學者，因其文獻早已喪失且「包含」一詞語意過於含混，已無法精確地用當代術語來加以表示。 中世紀哲學家們延續了斯多葛時期對條件句的討論，但問題似乎從「指示條件句的語意論為(1)至(4)中的哪一個？」轉移到「是否有好幾種在語意上不同的指示條件句？」這個問題之上。比方來說，Boethius便似乎認為至少有兩種不同的指示條件句，一種斷言其前後件間有某種必然性的關聯，另一種則否。但中世紀學者對指示條件句的討論過於晦澀，並且他們的討論與當時哲學家們對consequentia的看法夾雜不清。因而這些討論雖然有趣，成果卻不豐碩。 廿世紀對指示條件句語意論的主流立場基本上是回到了Philo的主張：”If

英语专项 语法 时态 12 条件句之零条件 讲解+练习+答案 zero conditional

Zero Conditional 零条件句 主谓模块 ? If people eat too much, they get fat. 如果人们吃得太多，就会发胖。 ? If you touch a fire, you get burned. 如果你碰了火，你会被烧伤的。 ? People die if they don't eat. 人不吃东西就会死。 ? Snakes bite if they are scared. 蛇害怕就会咬人 ? If babies are hungry, they cry. 如果婴儿饿了，他们会哭。 用法总结 This conditional is used when the result will always happen. So, if water reaches 100 degrees, it always boils. It's a fact. I'm talking in general, not about one particular situation. 当结果总是会发生时使用零条件句。所以，如果水达到100度，它总是沸腾。这是一个事实。这里指的是一般的正常情况，不是某个特定的情况。 The 'if' in this conditional can usually be replaced by 'when' without changing the meaning. 此条件中的“if”通常可以替换为“when”，其含义不变。 For example: If water reaches 100 degrees, it boils. (It is always true, there can't be a different result sometimes). 例如： 如果水达到100度，就会沸腾。 （这是一个科学事实）。 If I eat peanuts, I am sick. (This is true only for me, maybe, not for everyone, but it's still true that I'm sick every time I eat peanuts). 如果我吃花生，我就生病。 （只有我才是这样，也许不是每个人都是这样，但每次吃花生我都会生病）。The difference between the first and the zero conditionals is that the first conditional is about a specific situation, but the zero is talking in general. 第一条件句和零条件句的区别在于，第一条件句是关于一个特定情况的，而零条件句是指一般情况。

条件句与蕴涵

条件句Conditionals ?What's in an if? ?一个条件句就是一个具有“如果a，那么c”形式的句 子，我们用符号表示a→c来表示。逻辑学家把a称作条件句的前件，把c称作条件句的后件。 ?关于条件句最基本的推理是“假言推理”（modal ponens）：a，a→c/c。 ?不过，条件句确实令人迷惑不解的。 ?我们来看一下为何条件句是令人迷惑不解的。

?如果我们知道逻辑式a→c，那我们似乎可以推理得出? （a&?c）（肯定a同时否定c是不正确的）。 ?比如假设：如果你赶不上汽车，那么就会迟到。我们 可以推理得到，你会赶不上汽车而又不迟到为假。 ?相反，如果知道逻辑式?（a&?c），似乎我们据此推理 得到a→c。 ?比如假设，你去看电影不会不花钱（你去看电影而又 不花钱为假），可以推理得出，如果你去看电影，你就会花钱。

逻辑式?（a&?c）常写成a?c，被称为推论条件句。因此a→c似乎与a?c表达相同的意思。尤其当我们分析他们的真值时，它们必然具有相同的真值表。 a c a?c T T T T F F F T T F F T

?但是这张真值表很奇怪。它表明，如果c（后件）在一 个情形下（第一和第三行）为真，那么条件句a→c也为真。这似乎很难是正确的。比如，北京是中国的首都为真；但是条件句“如果北京不是中国的首都，那么北京就是中国的首都”很明显为假。 ?同样，如果a（前件）为假（第三行和第四行），那么 逻辑式a→c也为真。这也是很难是正确的。条件句 “如果南京是中国的首都，那么上海也是中国的首都” 很明显也为假。 ?那么哪里出错了呢？

英语语法——if第二条件句虚拟语气选择填空练习1verbs-second-conditional1

topic: CONDITIONALS: The second conditional structure 1 REMEMBER: The second conditional is used to talk about unreal situations in the present (things that are impossible, that won't happen, etc.) Choose the correct response for each of the sentences: 1. If my grandfather were younger, He _________ so many things. a) wouldn't forget b) didn't forget 2. If I _________ more money, I would buy a new car. a) would have b) had 3. If she had an umbrella, she _________ wet. a) wouldn't get b) didn't get 4. If we ________ a car, we would get there in 30 minutes. a) would have b) had 5. I ________ more careful if I were you. a) would be b) were 6. If animals could talk, I wonder what they ________? a) said b) would say 7. If she ________ harder, she would make more money. a) will work b) worked 8. If he changed jobs, He ________ much happier. a) will be b) would be 9. If it wasn't raining, we ________ to the beach. a) would go b) will go 10. You wouldn't feel so tired if you ________ more. a) will sleep b) slept

英语语法——if条件句混合训练选择填空练习1verbs-conditionals-mixed1

topic: CONDITIONAL TENSES For each sentence, choose the correct tense of the verb. 1. If I ________ you, I would apologize to her right away. (to be) a) was b) were c) have been 2. If I run into her, I ________ her that you're looking for her. (to tell) a) would tell b) tell c) will tell 3. If you ________ that again, I will call the police. (to do) a) to do b) do c) will do 4. He would never have asked her out on a date if she ________ him first. (to kiss) a) hadn't kissed b) didn't kiss c) will not kiss 5. If you were her, what ________? (to do) a) would you do b) did you do c) do you do 6. If she hadn't gone to England, she ________ Orlando Bloom. (to meet) a) would not meet b) did not meet c) would not have met 7. If it doesn't start snowing, we ________ this evening. (to go skiing) a) won't go skiing b) wouldn't go skiing c) don't go skiing 8. If you had saved some money earlier, you ________ broke right now. (to be) a) would not have been b) will not be c) are not 9. If I ________ at the airport so late, I would not have missed my flight. (to arrive) a) didn't arrive b) hadn't arrived c) would not arrive 10. If you buy one t-shirt, you ________ the second one free (to get). a) will have gotten b) would get c) get

人教版英语book6unit2grammarandusage虚拟条件句教案

Teaching plan for unreal conditionals Book6 Unit2 Grammar and usage 一．教学内容： 选修六第二单元语法知识的运用，虚拟语气---if引导的非真实条件句。 二．学习目标: 1. 知识与技能 让学生准确掌握虚拟语气在if非真实条件句中的用法，以达到熟练做题，并能在写 作中运用的目的。 2. 过程与方法 通过合作学习，学生能够学会知识迁移、逻辑推理、归纳整理的方法，并将其运用于解决实 际问题当中。 3. 情感、态度、价值观 培养学生发现问题、观察问题、分析问题的基本能力。锻炼学生的语言表达能力， 帮助学生体验学习乐趣从而树立自信。 三．学习重点难点： 重点：掌握虚拟语气在非真实条件句中主从句谓语动词的形式 难点：如何弄清楚虚拟语气在与现在、过去、将来事实相反的情况下，其主从句中谓语 动词形式的变化，特别是混合虚拟条件句。 四．教法学法： 教法：本节课贯彻“学生为主体，教师为引导”的教学思想。 学法：自主学习，合作探究法。 教学手段：自制多媒体课件，利用音频, 图片等材料。 五．教学过程： Step 1: Lead-in Listen to a song, If I Were a Boy, to introduce the topic in this class. Definition: Unreal conditionals are used to talk about situations that are not true or not likely to become true. Step 2: How to use correct tenses of unreal conditionals. 一．Unreal present: If I were a boy, I would go swimming in the river. If I were a husband, I would buy whatever my wife chose. If I were a student, I would take part in o ur school’s sports meeting 1.Question: What would you do if you were a boy/girl/...? _______________________________________________________________ 2.Listen to a song and finish the blanks. If I __________ (get) down on my knees and I pleaded with you If I _____________ (cross) a million oceans just to be with you __________ you ever __________(let) me down If I ______________(climb) the highest mountain just to hold you tight If I said that I would love you every single night ____________ you ever __________ (let) me down 3.Summary 1

IF的使用--零条件_第一条件_第二条件_第三条件

零条件_第一条件_第二条件_第三条件 if使用小窍门 在"if"引导的从句中，我们通常谈论不确定的事件和情况。 我们使用"if"来强调事情发生的条件。 另一种通常的用法是表明"if it is true that"。 特殊的时态能用于"if"之后来表示事情是想象中的。 最后，一个"if-clause"经常是这样的情形--一些事情必须在此之前发生，以后的事才能发生。 Zero Conditional: certainty We use the so-called zero conditional when the result of the condition is always true, like a scientific fact. 第一种情况我们称为“零条件”，在这种情况下由条件引起的结果通常都是事实，比如科学现象。 IF condition result present simple present simple If you heat ice it melts. First Conditional: real possibility We are talking about the future. We are thinking about a particular condition or situation in the future, and the result of this condition. There is a real possibility that this condition will happen. For example, it is morning. You are at home. You plan to play tennis this afternoon. But there are some clouds in the sky. Imagine that it rains. What will you do? 第二种情形，我们称之为“第一条件”，表示在将来某个条件或前提下，会产生某个结果。这个发生在将来的前提条件确实可能发生。 IF condition result present simple WILL + base verb If it rains I will stay at home. Second Conditional: unreal possibility or dream The second conditional is like the first conditional. We are still thinking about the future. We are thinking about a particular condition in the future, and the result of this condition. But there is not a real possibility that this condition will happen. For example, you do not have a lottery ticket. Is it possible to win? No! No lottery ticket, no win! But maybe you will buy a lottery ticket in the future. So you can think about winning in the future, like a dream. It's not very real, but it's still possible. 第三种情形，我们称之为“第二条件”，表示在将来某个条件或前提下，会产生某个结果。 这个发生在将来的前提条件不太可能发生，但仍有发生的可能性。 IF condition result

条件句第一讲：条件句的概述以及现在时态的条件句

条件句的概述： (1) 什么叫条件句？ 英文称作conditional sentences，指的是一个事实的发生需要依赖于另一个事实，也就是需要一个条件才能发生，所以叫条件句。 如果条件(condition) 存在，则结果(consequence) 发生 condition consequence (2) 条件句的分类： 条件句分为两种：真实条件句和虚拟条件句 真实条件句(real conditional)：条件和结果在日常生活中都是真实发生的 虚拟条件句(Unreal Conditional)：条件是假设的，想象的，通常都是不能实现的，换句话说，只能意淫，不能成真。这里看好了，是条件是假设的，假设完条件，结果建立在一个虚拟条件下，为真。 (3) 引导词，由if和when引导，if考点较多 区别点1： If：指单次发生，或者较少发生的条件。比如我一年去小明家一次，那就用if When：只习惯性发生的条件。比如我经常去小明家，那就用when 区别点2： If既可以用在真实条件句，也可以用在虚拟条件句 When只能用在真实条件句 (4) 从时态上来讲，分为四种： 现在present 过去past 将来future 混合mixed 一个一个来看，讲法是先现在时态，分为真实，和虚拟，然后过去…… 现在条件句(Present Conditionals) 1. 现在时态的真实条件句(Present Real Conditional) (1) 格式(form) [ If / When ... Simple Present ..., ... Simple Present ... ] [ If / When + 一般现在时态, 一般现在时态] [ ... Simple Present ... if / when ... Simple Present ... ] [ 一般现在时态+ if / when + 一般现在时态] (2) 用法：

英语语法——if第一条件句选择填空练习verbs-first-conditional1

topic: CONDITIONALS: The first conditional structure 1 Choose the correct response for each of the sentences: 1. If you _________ greasy food, you will become fat. a) eat b) will eat 2. If your sister goes to Paris, she _________ a good time. a) has b) will have 3. If he _________ that, he will be sorry. a) will do b) does 4. If I leave now, I ________ in New York by 8:00 PM. a) will arrive b) arrive 5. You ________ on your test if you don't study. a) won't do well b) don't do well 6. They won't know the truth if you ________ them. a) won't tell b) don't tell 7. If I bake a cake, ________ have some? a) will you b) do you 8. If he ________ you, will you answer the phone? a) will call b) calls 9. If you don't go to the party I ________ very upset. a) am b) will be 10. If you get a haircut you ________ much better. a) will look b) look

条件句第三讲：将来时态的条件句

将来条件句(Future Conditionals) 一涉及到将来时态，总是很麻烦，因为有俩变化形式will和be going to 1. 将来时态的真实条件句(Future Real Conditional) (1) 格式(Form) [ If / When ... Simple Present ..., ... Simple Future ... ] [ If / When + 一般现在时态, 一般将来时态] [ ... Simple Future ... if / when ... Simple Present ... ] [ 一般将来时态+ if / when + 一般现在时态] Examples: ?If I go to my friend's house for dinner tonight, I will take a bottle of wine or some flowers. I AM STILL NOT SURE IF I WILL GO TO HIS HOUSE OR NOT. (将来如果我有机会去朋友家吃饭，我讲会带一瓶酒和一些鲜花过去。这件事是可能发生的) 条件：如果将来我去朋友家吃饭 结果：我讲会带一瓶酒和一些鲜花过去 真实性：未来真实。未来有可能去朋友家吃饭。 时态：一般将来，说明将来我很可能这么做。 其他例子不一一分析，自行按照上述方法分析，写出条件，结果，真实性和时态?When I have a day off from work, I am going to go to the beach. I HAVE TO WAIT UNTIL I HAVE A DAY OFF. ?If the weather is nice, she is going to walk to work. I T DEPENDS ON THE WEATHER. ?Jerry will help me with my homework when he has time. I HAVE TO WAIT UNTIL HE HAS TIME. ?I am going to read if there is nothing on TV. I T DEPENDS ON THE TV SCHEDULE. ?A: What are you going to do if it rains? B: I am going to stay at home. (2) 用法： The Future Real Conditional describes what you think you will do in a specific situation in the future. It is different from other Real Conditional forms because, unlike the present or the past, you do not know what will happen in the future. Although this form is called "real", you are usually imagining or guessing about the future. It is called "real" because it is still possible that the action might occur in the future. Carefully study the following examples and compare them to the Future Unreal Conditional examples further down the page.

条件句第二讲：过去时态的条件句

过去条件句(Past Conditionals) 1. 过去时态的真实条件句(Past Real Conditional) (1) 格式(Form) [ If / When ... Simple Past ..., ... Simple Past ... ] [ If / When + 一般过去时态, 一般过去时态] [ ... Simple Past ... if / when ... Simple Past ... ] [ 一般过去时态+ if / when + 一般过去时态] (2) 用法： The Past Real Conditional describes what you used to do in particular real-life situations. It suggests that your habits have changed and you do not usually do these things today. 过去时态的真实条件句用来谈论现实生活中过去你做的事情。它表明你过去的习惯已经变了，现在不这样了，所以你用过去时态，而之所以叫真实的，是以为过去你确实是这么做的。 Examples: ?If I went to a friend's house for dinner, I usually took a bottle of wine or some flowers. I don't do that anymore. (过去如果我去朋友家吃饭，通常我会带一瓶酒和一些鲜花过去。) 条件：如果我去朋友家吃饭 结果：我会带一瓶酒和一些鲜花过去 真实性：真实。平时确实是这么做的。 时态：一般过去，说明过去我一直这么做，现在不这么做了。 其他例子不一一分析，自行按照上述方法分析，写出条件，结果，真实性和时态?When I had a day off from work, I often went to the beach. Now, I never get time off. ?If the weather was nice, she often walked to work. Now, she usually drives. ?Jerry always helped me with my homework when he had time. But he doesn't do that anymore. ?A: What did you usually do when it rained? B: I usually stayed at home. (3) used to的使用 Used to可以用在过去时态的真实条件句中，表达过去的习惯，所以上述例句统统可以改成如下，而且意思不变。 Examples: ?If I went to a friend's house for dinner, I used to take a bottle of wine or some flowers. I don't do that anymore. ?When I had a day off from work, I used to go to the beach. Now, I never get time off. ?If the weather was nice, she used to walk to work. Now, she usually drives. ?Jerry used to help me with my homework when he had time. But he doesn't do that anymore.