MODALS: DEDUCTION

MODALS : DEDUCTION; COMPOUND FORMS
Modal verbs can be used to expressed different degrees of certainty. Here is a list starting from the maximum level and ending with the least level of certainty.

MODAL VERBS EXPRESSING DEDUCTION

MUST
Almost certain (80%)
That must be Cheryl`s car. (I`m quite sure it is)

SHOULD
Very likely (60%)
That should be Cheryl`s car. (I think it is)

COULD
Possible (50%)
That could I may be Cheryl`s car. (I can`t tell)

MIGHT
Uncertain (40%)
That might be Cheryl`s car. (I have no idea)

MUST
Very uncertain (20%)
That may not be Cheryl`s car. (I have no idea)

MAY /
MIGHT NOT
Impossible (10%)
That can`t be Cheryl`s car. (I`m sure it isn`t)


The same can be done with modal verbs in the Past form. The compound form of modal verbs is basedMon this typical structure:

MODAL ♦ HAVE ♦ PAST PARTICIPLE (PP)

MUST HAVE + P.P.
Almost certain (80%)
The film must have been boring.

COULD HAVE + P.P.
Possible (50%)
She could have left her phone at home.

MAY (not) HAVE + P.P.
Uncertain (40%)
He may have known the killer.

MIGHT (not) HAVE + P.P

They mightn`t have recognised us.

CAN’T HAVE + P.P.
Impossible (10%)
I can`t have signed this document.


OTHER COMPOUND MODALS

SHOULD (not) HAVE + P.P.
Expressing regret
about something that
didn`t happen in the
past
We shouldn`t have wasted so much money on that

OUGHT TO HAVE + P.P.

She ought to have taken that chance.

MAY (not) HAVE + P.P.

I could have studied harder.

DON’T / DIDN’T NEED TO or NEEDN’T HAVE + P.P.


In the Past tense there is a little difference between these two forms. Compare the examples:
- Ann told us we didn`t need to bring any drinks.
(we knew it wasn`t necessary to do it).
- We needn`t have brought the umbrellas: it was sunny all day.
(but we didn`t know that when we left.)



OTHER FORMS EXPRESSING DUTY, OBLIGATION AND NECESSITY
( Be expected to is used when something is very likely to happen, we expect it to happen:
- The storm is expected to move southward during the night.
( Be obliged/compelled /forced to are used when an action is caused by something:
- Because ofthe flood we wereforced to close down.
( Be bound to is used when something is destined to happen or will happen for sure:
It was bound to happen sooner or later. We should have known better.
( Be due to it is used for things dial are planned or expected to happen at a certain time or moment:
- Our train is due to arrive at Glasgow Central at 12:12.
( Be to is used as a short form for ‘be going to’ (especially in the news) or to give formal / impersonal instructions and orders about actions that must or mustn`t be carried out:
- The Pope is to visit the Philippines (or:...is going to visit...) .
- The rest papers are to he handed in by 9.30AM. (or:...must he handed in...)
- Guests are to leave the premises in a clean and tidy condition, (or must leave...)
( Be meant to is similar to be bound to and is used when something is destined Io happen:
- Laura was meant to he a mother: she`s so patient and loving.

PRACTICE
I. 1 What are the 8 speakers doing? Match the sentences (1-8) to the correct function (a-h).
1. When is it due to snow in Birmingham?
2. You weren`t expected to arrive so early!
3. I should have listened to her when she said I was wrong.
4. Tara mightn`t have received our text message.
5. You can’t be 50: you look so much younger.
6. We’re bound to hear from that man again.
7. You needn`t have brought any wine.
8. You must have a lot of spare time.
a. making inferences about the past
b. expressing regret
c. making inferences about the present
d. saying that something is impossible
e. predicting that something will happen again
f. expressing surprise
g. asking when something is expected to happen
h. explaining that something was not required

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