MODAL AUXILARY “Degree of Certainty”

Degree of certainty is how we use modals for explaining how much our certainty about something, how sure we are (certainty, probability, possibility, and impossibility).

11. Degree of certainty : present time

If you are sure about what you said, you can use to be/verb (100% sure)

Ex:

-> why is not Jane in class ?

*Jane is sick ( I am sure that Jane is sick. Last night, she said to me she would not come to class because got flu)

-> do you know where Jane goes ?

* Jane goes to market ( I just  met her in road, she would buy eggs for her mom, she said)

Must (95%) expresses a strong degree of certainty, but less than 100%.

It can be logical conclusion.

Ex:

*Jane must be sick ( usually she is in the class every day, but I saw her last night, she was not feeling good)

*Jane must go to market ( I just saw her in the road, she walked to market)

May/ Might/Could (less than 50%) it  just  expresses  a  guess, maybe, perhaps(possibility).

Ex:

*Jane may/might/could be sick ( I do not really know, she may be at home watching  tv.  She might be at library or she could be out of town)

   2. Degree of certainty: present time negative

-> ”there is a party at John’s home” Why does not Jane eat ?

*she is not hungry (she said,  she just ate  before went  here)

Could not/can not (99%) it will be impossibility

*she could not/can not get hungry ( it is impossible. I just saw her eating  4 pieces of pizza and she wanted to eat again ? I do not believe it)

                                                                                                                            

          Must not(95%)  logical conclusion

*she must not  get hungry ( Jane is not eating her food. That is the only reason I can think of.)

May not/might not(less than 50%)

*she may not/might not get hungry. (I do not know. I just came here. She might not be  feeling good or she has eaten before I came.)

3. Degree of certainty : past time

It has the  same certainty. Just about time(past)

The formula : modal + have +(been or V3)

->Why was not Jane in the class ?

* she was sick

*she must have got sick

*she might/may/could have got sick

Note : simple way to understand  is it depends  who is speaking up. It might be different for  everyone.

Where does Siska go ?

Asep : she goes to library. I just met her.

Jamal : she must go to library because she will persentate tommorrow.

Permana : I dont really sure. She might go to library

I hope it will help you to undersand. Thanks for have visited my blog.

See you in the next post.

Reference : Betty Schrampfer Azar, English Grammar-Third Edition