Modals

Will / Might

Expressing degrees of certainty

Present and Future Uncertainty

VERY CERTAIN	ALMOST CERTAIN	UNCERTAIN
statement Polar bears are starving. (dying of hunger) Polar bears will die of starvation. Polar bears are going to disappear.	Polar bears must be starving. (Use must to express a logical conclusion, a sure guess based on clues, information known to the speaker. This does not mean strong advice.)	Polar bears may/ might/ could be starving. Polar bears may/ might/ could disappear.
negative Polar bears won't starve.	Polar bears must not be starving. Polar bears can't/ couldn't be starving. 99%	Polar bears may/ might not be starving. Polar bears may/ might not disappear.
within a statement I am sure that polar bears are die of starvation.	It is unlikely that polar bears will disappear. It is doubtful that polar bears will disappear.	It is possible that polar bears will disappear. Polar bears will possibly disappear.
The speaker is 100 % certain that they will disappear.	The speaker is 95 % certain they are disappearing.	The speaker is 50% certain they will disappear.

VERY CERTAIN

ALMOST CERTAIN

UNCERTAIN

statement

Polar bears are starving. (dying of hunger)

Polar bears will die of starvation.
Polar bears are going to disappear.

Polar bears must be starving.

(Use must to express a logical conclusion, a sure guess based on clues, information known to the speaker. This does not mean strong advice.)

Polar bears may/ might/ could be starving.
Polar bears may/ might/ could disappear.

negative

Polar bears won't starve.

Polar bears must not be starving.
Polar bears can't/ couldn't be starving. 99%

Polar bears may/ might not be starving.
Polar bears may/ might not disappear.

within a statement

I am sure that polar bears are die of starvation.

It is unlikely that polar bears will disappear.
It is doubtful that polar bears will disappear.

It is possible that polar bears will disappear.
Polar bears will possibly disappear.

The speaker is 100 % certain that they will disappear.

The speaker is 95 % certain they are disappearing.

The speaker is 50% certain they will disappear.

starve (v.) to die of hunger; starving (adj.) or (participle) ; starvation (n.) – suffering or death caused by lack of food.
clue (n.) – information that helps you understand the reasons why something happens

Past Uncertainty

VERY CERTAIN – Reflection	ALMOST CERTAIN – Deduction	UNCERTAIN – Speculation
statement Polar ice melted. Polar bears lost their icy habitat.	Polar bears must have lost their food supply (Clues: there is no ice, so there are no seals. Polar bears have no platforms from which they can hunt seals.)	Polar bears may/ might/ could have left their cubs.
negative Polar bear cubs didn't die from the cold.	Polar bears could not have fed their cubs.	Polar bears may/ might not have found food for their cubs.
within a statement I am/was sure that polar bear cubs died from starvation	It is/was likely that polar bears found no seals to feed their cubs.	It is/was doubtful that the polar bears found any ice from which to hunt seals.

VERY CERTAIN – Reflection

ALMOST CERTAIN – Deduction

UNCERTAIN – Speculation

statement

Polar ice melted.
Polar bears lost their icy habitat.

Polar bears must have lost their food supply (Clues: there is no ice, so there are no seals. Polar bears have no platforms from which they can hunt seals.)

Polar bears may/ might/ could have left their cubs.

negative

Polar bear cubs didn't die from the cold.

Polar bears could not have fed their cubs.

Polar bears may/ might not have found food for their cubs.

within a statement

I am/was sure that polar bear cubs died from starvation

It is/was likely that polar bears found no seals to feed their cubs.

It is/was doubtful that the polar bears found any ice from which to hunt seals.

reflection (n.) – remembering the past
deduction (n.) – a logical conclusion, based on information known to the speaker.
speculation (n.) – an educated guess

Must (conclusion) vs. Must (necessity)

CONCLUDING THAT SOMETHING IS CERTAIN	NECESSITY AND OBLIGATION
A speaker uses must to express a logical conclusion, a sure guess based on clues, information known to the speaker.	A speaker also uses must to express obligation or necessity, something that someone "has to do" (strong advice).
Polar bears go into seaside towns looking for garbage. Polar bears must be hungry.	Polar bears must be fed or relocated. (should, need to)
Ice used to cover the polar regions all year. Polar bears must miss their polar habitat.	Polar bears must swim long distances to find ice and seals to eat.
A normally peacefu lbear attacked and killed some arctic campers. The bear must have been looking for food.	The campers had to shoot the bear. (Neccesity in the past tense is expressed with "had to" not "must have".)

Sentence Structure

AUX VERB	SUBJECT	MODAL	VERB BASE	COMPLEMENT	TAG CLAUSE
STATEMENT	Polar bears	could	die	of starvation.
		may / might
		must	be	hungry.
QUESTION Could	polar bears		die	of starvation?
*May/ Might
Is it possible that	polar bears	will	die	of starvation?
TAG QUESTION	Polar bears	could	die	of starvation,	could n't they?
		may/ might			*may/ might they not?
		must	be	hungry.	must n't they?
It is possible that	polar bears	will	die	of starvation.	isn't it?
NEGATIVE	Polar bears	may / might not	die	of starvation.
	Polar bears	may not	die	of starvation.
	Polar bears	could not	die	of starvation.
It is doubtful that It is unlikely that	polar bears	will	die	of starvation.
PAST	Scientists	might have	predicted	this.
	Scientists	may have	predicted	this.
	Scientists	could have	predicted	this.
NEG. PAST	Scientists	might not have	predicted	this.
	Scientists	may not have	predicted	this.
	Scientists	could not have	predicted	this.
W / ADVERB	We	might suddenly	lose	this species.
	We	may eventually	lose	this species.
	We	could also	lose	this species.
It is possible that Possibly,	we	will soon	lose	this species.

*awkward sounding
complement – a word, phrase or clause which is necessary in a sentence to complete its meaning
A tag question can also occur with a negative main sentence and a postive final question: Polar bears couldn't die, could they? And so / too (tag questions)

Related page: Modal Agreement

Practice 1

How Certain is the Speaker?

Decide what the meaning of the verb in the sentence is.

Select the response that best completes the sentence.
Read the text box to the right for feedback.

	Feedback	YOUR RESPONSE
1	Stephen King's latest work could be a nightmare for book publishers. The writer is sure (about future event) The writer is uncertain (about future event) The writer is reflecting (on a past event)	Feedback 1
2.	He will publish his books on the Internet. He is sure (about future event). He thinks so (about future event) . He is speculating (on a past event).	Feedback 2
3.	The first chapter will be free. Then he might ask readers to pay $1 for the next chapter. He is sure (about future event) . He is uncertain (about future event). He is speculating (on a past event)	Feedback 3
4.	If enough readers pay $1, he will write the next chapter in the series. This event is scheduled. This event is not scheduled.	Feedback 4
5.	In the past, King's dealings with publishers have been unsatisfactory. They might not have shared profits with him. The writer is sure about a future event. The writer is uncertain about future event. The writer is speculating on a past event.	Feedback 5

Practice 2

Expressing Doubt and Certainty

Decide which modal can complete the sentence.

Select the response that best completes the sentence.
Read the text box to the right for feedback. An asterisk * indicates an incorrect repsonse.

#	Feedback	YOUR RESPONSE
6.	The Internet several new writers to publish their works. will enable might enable might not enable	Feedback 6
7.	Several writers how to present their materials on web sites. will know may know may not know	Feedback 7
8.	Many people thought that copyright laws difficult to enforce. may be might be might have been	Feedback 8
9.	Writers who publish on the Internet to profit from their web publishing. will expect may expect could expect	Feedback 9
10.	Publishers a trend in lower sales of printed books that is occuring now. might not predict may predict might not have predicted	Feedback 10
11.	In the future, all books sold as digital copies to be read on handheld devices or to be printed on personal printers. may be sold might be sold will be sold	Feedback 11
12.	Clearly, some people ready to give up a book that they can hold in their hands and turn its pages. may be may not be might not be	Feedback 12

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