Lecture 20 Epistemic Use of Modals Objectives: 1. Epistemic and Non- epistemic use of modals 2. Epistemic use of modals 3. Epistemic use of Modal+ perfective

Lecture 20 Epistemic Use of Modals

• Objectives:

• 1. Epistemic and Non- epistemic use of modals

• 2. Epistemic use of modals

• 3. Epistemic use of Modal+ perfective infinitive


As we know, modals are mostly molysemous.

In terms of the meanings they express, models can be divided into two categories---epistemic and non-epistemic .

The non-epistemic category only describes the fact as it .

The function of Epistemic models is to make judgments about the possibility or necessity that something is or is not the case.


1. Epistemic and Non-epistemic functions of modals

ModalsModalsNon-epistemic use Epistemic use

can/could Ability, permission possibility

may/might permission possibility

will/ would Volition(意志 ) Predictability(推测 )

should /ought to obligation logical necessity

must obligation logical necessity

1. Epistemic and Non-epistemic Functions of Modals

• There are nine modals that have both

• epistemic and non-epistemic functions.

• In their epistemic uses, the above models can be arranged on a scale according to the degree of certainty or uncertainty

“Might” can be viewed as the most uncertain, while “must” as the most certain. The scale is as follows:

Uncertain Might Possibility May Could

Can Should

Ought to Would

WillCertain must probability



• From the above, we can see that

• “ might, may, could, can” refer to possibility; “should, ought to , would, will” to probability ,“must” to certainty.

Generally speaking, there are three forms of epistemic modals we take “Must” as an example

1) Must do (must + present infinitive) 2) Must be doing (must+ progressive infinitive) 3) Must have done (must+ perfective infinitive)

4) Must have been doing (must+ perfective progressive infinitive)

1) and 2) express possibility/ speculation about present or future event ,

3) and 4) express possibility about past event

2. Epistemic Use of Modals

1) Epistemic Use of Must --He must live here. ( I am sure he lives here.) -- He must be living here. ( I am sure he is living here.)

-- He must have lived here. ( I am sure he lived here.) --He must have been living here. ( I am sure he was living here)



• 1) Epistemic Use of Must

• Note :

• “must” denoting necessity is generally used in positive statements (affirmative statement) while in question and negative statement, “ can” and “can't” should be used instead.

• 1) Epistemic Use of Must

--He has a house in London and another in Paris. So he must be rich.

-- I have had no sleep in 48 hours. You must be exhausted.

-- I keep meeting him on the bus. He must live/ must be living nearby.


1) Epistemic Use of Must

-- The police stop all cars. They must be looking for the escaped prisoner.

-- He did not wake up till lunch time.He must have taken sleeping pills last night.

-- It was a head – on collision, but the drivers were not hurt.They must have been wearing their seat belts.




• Note : The negative equivalent of “must” is “can't”.

• --There must be a mistake.

• --There can’t be a mistake.

• --She can’t be in the dormitory, I saw her making for the library.

The past forms of epistemic modals (Must have done ) are realized by adding a perfective infinitive to show assumption arrived at by inference of the thing which occurred in the past.




• 1) Epistemic Use of Must • --You must have left your handbag in the

theatre.• -- Her eyes are red. She must have been crying.• --He must have been through a lot.• --They must have arrived by now.• --They are sweating all over.• --They must have been working in the fields.

2) Epistemic Use of can/Could

--Where can/could he be? --He must/may/might/can't be in the office.--He may be reading in the classroom.

--Yesterday I couldn't find him, he may have gone to the station.--He may have been waiting for us.


2) Epistemic Use of may/might

May / might do

May / might be doing

May / might have done

He may / might have gone.



• 2) Epistemic Use of may/might

• --He may / might tell his wife.• --Ann may / might know Tom’s address. • --He may / might be waiting at the station• --He said that she might have missed the plane.• --Perhaps we should have taken another road. • It might have been quicker.

3) Epistemic use of Ought to /should

--The letter should have arrived by now.

--We ought to have given you more help.

--She would have done anything to make amends.



• 3) Epistemic use of Ought to /should

• --The letter should have arrived by now. • --We ought to have given you more help.

• Note: Could / might is more polite, but should is the more usual form.

• You could (might) have been more careful.• You oughtn’t to be talking so much. • She might still be thinking about the questions you raised.

3) Epistemic use of Ought to /should Note: To talk about things which did not happen though they were supposed to , we can use should / ought to have done.

--They shouldn’t have left so soon.

--There is no reason why he should have refused.



• 4) Epistemic use of will/would• will/would do• will/would be doing• will/would have done

• -- Ring his home number. He’ll be at home now. • --He’ll be expecting a call from you. • --He’ll have finished his supper. • --The guests would have been arriving by now. • .

5) Needn’t + perfective infinitive (Needn’t have done)implies that something was done but it was unnecessary.

--You needn’t have been worrying about it.

--I needn’t have written to him, because he phoned me shortly afterwards.


Exercises from CET-band 4

(1) Investigators agreed that passengers on the airliner ______ at the very moment of the crash. (CET-2002.6-67)

A)should have died B) must be dying C) must have died D) ought to die

(2)The careless man received a ticket for speeding. He_____ have driven so fast (CET-2003.1-33) A) can’t B) wouldn’t C) shouldn’t D) mustn’t

(3)He said that the driver must have had an accident; otherwise he _______by then. (CET-2003.1-56A) would have arrived B) must have arrivedC) should arrive D) would arrive)

（ 4 ） As teachers we should concern ourselves with what is said,

not what we think ________. A) ought to be said B) must say C) have to be said D) need to say

(5) This box is too heavy, ________ give me a hand?

A)would you mind B) would you please B)C) will you like to D) will you please to

(6) It was very kind of you to do the washing-up, but you __________ it. A)mustn’t have done B) wouldn’t have done

C) mightn’t have done D) didn’t have to do

(7) Research findings show we spend about two hours dreaming every night, no matter what we ___________ during the day.

A)should have done B) would have done C) may have done D) must have done

• 8) Some women ______________ a good salary in a job instead of staying home, but they decided not to work for the sake of the family.

• A) must make B) should have made• C) would make D) could have made

•

• 9) You _______ him so closely; you should have kept your distance. (• A) shouldn’t follow• B) mustn’t follow• C) couldn’t’ have been following• D) shouldn’t have been following

• 10) The millions of calculations involved, had they been done by hand, __________ all practical value by the time they were finished. (2001,6, 33)

• A) had lost • B) would lose• C) would have lost • D) should have lost• • Answer : CCAA ＢＤＣ DDD

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Lecture 20 Epistemic Use of Modals Objectives: 1. Epistemic and Non- epistemic use of modals 2. Epistemic use of modals 3. Epistemic use of Modal+ perfective