08 助动词与情态动词：给主要动词叠加时间、语态和态度

本章学习目标

学完本章，你应该能够：

1. 判断 be, have, do 是助动词还是实义/系动词。
2. 按正确顺序理解和构成助动词链。
3. 掌握核心情态动词的形式规则和主要意义。
4. 区分义务、禁止、不必要以及事实推测。
5. 用 modal + have + 过去分词 判断过去可能性、遗憾或批评。

学前诊断：情态动词说的是动作时间，还是说话人判断

She must have left already 表示“她当时必须离开”，还是“说话人推断她已经离开”？

1. 核心直觉：主要意义不变，语法视角可以叠加

从主要动词 review 开始：

• They review the report. 普通陈述
• They are reviewing the report. 进行
• They have reviewed the report. 完成
• The report was reviewed. 被动
• They may review the report. 可能
• They do not review every report. 否定

助动词不是可有可无的装饰。它们决定句子怎样定位事件、怎样形成否定和疑问，以及说话人对事件持什么态度。

2. 助动词链的固定顺序

英语助动词通常按以下顺序排列：

情态动词 → 完成 have → 进行 be → 被动 be → 主要动词

例子：

The application may have been rejected.

• may：可能
• have + rejected：从现在回看此前
• be + rejected：被动

更复杂但较少见：

The system may have been being tested.

它符合“情态 → 完成 → 进行 → 被动”的顺序，但实际写作通常会改写以提高可读性。

每个助动词决定后一个词的形式：

3. 基本助动词 be, have, do

3.1 be

作进行助动词：

They are checking the figures.

作被动助动词：

The figures were checked twice.

作系动词：

The figures are accurate.

判断依据是它后面的形式和整句功能，不是看到 be 就统一叫助动词。

3.2 have

作完成助动词：

They have checked the figures.

作实义动词：

They have enough evidence.

完成助动词后必须接过去分词；实义 have 表拥有、经历、进行活动等。

3.3 do 与 do-support

当普通实义动词需要构成否定、一般疑问或强调时，英语常加入 do/does/did：

• They do not agree.
• Does she agree?
• I did check the address.

加入 does/did 后，主要动词恢复原形：

• 错误：Does she agrees?
• 正确：Does she agree?

句中已有 be 助动词、完成 have 或情态动词时，不再加入 do：

• Is she working?
• Has she finished?
• Can she attend?

4. 情态助动词的共同形式

核心情态助动词：

can, could, may, might, must, shall, should, will, would

共同特点：

1. 后接动词原形：may leave。
2. 第三人称单数不加 -s：she may leave。
3. 否定直接加 not：may not leave。
4. 疑问直接与主语倒装：May she leave?
5. 通常没有普通不定式、分词或完整时态变化，因此常借半情态结构补足。

同一个情态动词常有两大意义方向：

• 行为控制：能力、许可、义务、意愿。
• 事实判断：说话人认为事情多可能、多确定。

5. can / could / be able to

能力

• She can speak three languages. 当前一般能力。
• She could read at the age of four. 过去一般能力。

过去某次具体成功常用 was/were able to 或 managed to：

Despite the noise, she was able to finish the task.

许可和请求

• Can I use this chair? 日常许可。
• Could you open the window? 更委婉的请求；could 不一定表示过去。

可能性与推断

• Mistakes can happen. 一般可能。
• That can't be correct. 说话人认为不可能正确。

过去本可做到

You could have called me.

常暗示过去具备可能或机会，但实际没有做，也可能带轻微批评。

6. may / might

可能性

• The meeting may be delayed.
• The meeting might be delayed.

might 常显得更不确定或更试探，但二者并非可以用固定百分比区分。

许可

You may leave now. 较正式。

过去可能

She may/might have missed the train.

表示对过去情况的不确定推测。

may not 有两种可能：

• 可能没有：She may not know the answer.
• 不被允许：Visitors may not enter this area.

要由语境区分。

7. must / have to / need to

7.1 强义务

You must submit the form today.

must 常表达说话人认为必要、规则要求或强烈指令。

have to 常表达外部条件或客观需要，也能完整变化时态：

• I have to leave.
• I had to leave early yesterday.
• I will have to leave soon.

7.2 禁止与不必要

• You must not enter. = 禁止进入。
• You do not have to enter. = 不必进入，可以选择。
• You need not enter. = 不必进入，较正式。

`mustn't` 是“禁止”，不是“不必”。

7.3 肯定推测

She must be at work. 根据证据推断她一定在工作地点。

过去推测：

She must have left already. 推断她已经离开。

否定推测通常用 can't/couldn't，不使用 mustn't：

She can't have left; her coat is still here.

8. should / ought to / had better

建议和责任

• You should check the figures again.
• You ought to check the figures again.

ought to 后有 to，与核心情态动词的形式不同。

预期

The train should arrive by six. 表示按正常情况预计如此。

过去未做到或不该做

• You should have checked the address. 应该检查，但没有。
• You should not have shared the file. 不该分享，但分享了。

强烈建议或警告

You had better leave now.

had better 后接原形，形式中的 had 不表示普通过去。否定为 had better not。

9. will / would / shall

will

• 将来预测：The plan will take two weeks.
• 意愿/承诺：I will help you.
• 典型倾向：Accidents will happen.

would

• 过去视角下的将来：She said she would call.
• 反事实结果：I would help if I had time.
• 礼貌请求：Would you close the door?
• 过去习惯：Every summer, we would visit our grandparents.

看到 would 必须结合参照点和句型判断，不能统一翻成“将会”。

shall

现代英语中范围较窄：

• 提议：Shall we begin?
• 正式规则/法律文本中的义务或规定。

普通将来表达通常使用 will。

10. need 与 dare 的两种身份

情态用法

• Need we wait?
• You needn't worry.
• Dare he disagree? 较正式或文学化。

实义动词用法

• Do we need to wait?
• You don't need to worry.
• He doesn't dare to disagree.

判断线索是：是否使用 do、后面是否带 to、是否有人称和时态变化。

11. used to 与两个相似结构

• used to + 动词原形：过去常常如此，现在通常不再如此。
  • I used to work at night.
• be used to + 名词/doing：习惯于。
  • I am used to working at night.
• be used to + 动词原形：被用来做。
  • This tool is used to measure distance.

三者中的 to 身份不同，后面形式也不同。

12. 其他常见半情态结构

这些结构能补足核心情态动词缺少的时态和非谓语形式。

13. 情态完成式：现在判断过去

结构：modal + have + 过去分词

14. 阅读助动词链

The figures could not have been checked carefully.

1. could：情态，可能表示推断或能力相关意义。
2. not：否定作用于情态判断。
3. have + been：完成，指向此前。
4. be + checked：被动，数据是被检查的对象。
5. carefully：方式。

在“否定推断”语境中，整句可理解为：这些数据不可能已经被认真检查过。

15. 写作时的五项检查

1. 需要表达的是能力、许可、义务、建议还是事实推测？
2. 时间是现在/将来，还是对过去作判断？
3. 情态动词后是否使用原形？
4. 助动词顺序和后续形式是否正确？
5. 否定究竟表示禁止、不必要还是不可能？

16. 高频错误

1. She can speaks English. → She can speak English.
2. He doesn't can attend. → He cannot attend.
3. You mustn't come if you are busy. 若意思是“不必”，改为 You don't have to come ...
4. She mustn't be at home. 若是否定推测，改为 She can't be at home.
5. I am used to work late. → I am used to working late.
6. You should checked it. → You should check it.；谈过去遗憾则 should have checked。

17. 快速复习清单

• 助动词链顺序是情态、完成、进行、被动、主要动词。
• be/have/do 的身份由句中功能决定。
• 情态动词后接原形，不加第三人称 -s。
• mustn't 表禁止，don't have to/needn't 表不必。
• 过去推测或遗憾常用 modal + have done。
• would 可能表示过去将来、反事实、礼貌或过去习惯。
• used to do、be used to doing、be used to do 必须区分。

18. 自检题

题目

1. 判断 be 的身份：She is working 与 She is confident。
2. 改错：Does he knows the answer?
3. 按顺序分析：The application may have been rejected.
4. 选择：You mustn't / don't have to attend; the session is optional.
5. 选择：She mustn't / can't be the author; she was abroad then.
6. 填空：You ___ (should/check) the address before you left.（过去没检查）
7. 解释：Could you help me? 中 could 是否一定表示过去？
8. 改错：I am used to get up early.
9. 区分：The device is used to measure temperature 与 I used to measure temperature by hand。
10. 填空：She said she ___ call later. (will / would)
11. 用 may have done 写一句对过去的可能推测。
12. 将 You needn't wait 改为实义动词 need 结构。