Modals Part Eight

Skill: Grammar  

Category: General English & Academic English

Level: Upper-Intermediate

Modals

Part Eight

Expressing Past Ability:

To express past ability, could, was/were able to should be used. For past ability, was or were able to is more common than could.

Present:                      I can edit and revise my assignment myself.

Past:                            I could edit and revise my assignment myself.

Present:                      I am able to fix the burnt spaghetti.  

Past:                            I was able to fix the burnt spaghetti. 

Degree of certainty in present time:

When we want to express how much we are sure about something to happen, we use modals to show degree of certainty.

100 % Sure:

When we are completely sure about an action, we necessarily don’t use any modals. For example, if I say, “Stephen is on a trip to Canada.” I am expressing a fact and I am sure and the degree of certainty is 100 %.

Must: It expresses a strong degree of certainty about an action in present time, but yet it is not 100 %.

Ex: Why isn’t Stephen in the class today? He must be on a trip to Canada.

Note. The speaker has a logical conclusion and some evidence to make him believe; he can be certain for 95 percent, not for 100.

50 % sure or less:

The modal auxiliaries like may, might and could express weak certainty.

Ex: Where is Stephen?

            – He may be on a trip to Canada.

            – He might be on a trip to Canada.

            – He could be on a trip to Canada.

Note. The auxiliary can does not express any degree of certainty.

Ex: INCORRECT: He can be sick.

Negative form of degree of certainty in present time:

100 % sure:                 Stephen isn’t thirsty.

99 % sure:                   Stephen couldn’t be thirsty.

                                    Stephen can’t be thirsty.

95 % sure:                   Stephen must not bethirsty.

50 % sure or less:        Stephen may not be thirsty.

                                    Stephen might not be thirsty.

• Stephen doesn’t want anything to drink. He isn’t thirsty. He told me that he drank a bottle of water before he came here. I heard it and I believe it.
• Stephen couldn’t or can’t be thirsty. It is not possible that the could be thirsty, because I just saw he drank water. I don’t believe it.
• Stephen doesn’t drink water. He must not be thirsty and that is the only reason that I can think of.
• I don’t know why Stephen doesn’t drink the water. He may not be thirsty or maybe he doesn’t feel well now.