In this lesson, you will focus on the use of modal verbs to express near certainty in the present and general truths.
Certainty
When you know that something is true or not true about the present, you can use present tenses to express this.
- Russia is the largest country in the world, but China has the most people.
However, at times, you may want to express that you are almost certain that something is true or not true. In this case, you can use must and can’t to express a high degree of present probability or improbability.
Must
Must is used when someone is quite certain about something, but they do not have all the facts.
- The lights are on inside his house, so Kieran must be home.
- The dog must be hungry because he keeps looking at his empty food bowl.
- People have been gathering at the government building since about nine o’clock. They must be protesting something.
Can’t
To express that something is improbable or unlikely in the present, can’t is used, not mustn’t. Can’t expresses the idea that something is most likely not possible.
- She can’t be a police officer because she’s not wearing the correct uniform.
- Jameel can’t be creating the new language policy for the department! Maria asked me to do it last week.
- He can’t be a professional actor; he keeps forgetting his lines.
General Truths
General truths are observations about the world. Like expressions of certainty, they are often expressed with present tense verbs.
- Family is important to most people.
The modal verb can is used in a similar way.
Can
As you saw in English 125, can is often used to express ability. However, it is also possible to use can to describe general truths about what something is like or how someone often behaves. Unlike must or can’t, this function of can isn’t used in the continuous form because it focuses on general ideas and is not connected to time.
- Anybody can learn a language if they have time and motivation to study.
- People can practise any religion they want in Canada.
- The company’s ideas about cultural inclusivity can be insensitive at times.
It is also used in its negative form.
- One person can’t change the world all by themselves.
- A language can’t survive if it doesn’t have speakers.
Exercise
Speaking Practice
With your partner, decide who will be Student A and who will be Student B. Then, tell your partner about each of your situations. Take turns. Respond to your partner’s situations by expressing a present probability, improbability, and/or general truth.
You see a man looking around at the ground and repeatedly putting his hands in his pockets.
He must be nervous about something. He can’t be confident.
- You see a man looking around on the ground and repeatedly putting his hands in his pockets.
- You see people lining up to enter a store.
- You know that learning a language requires a lot of hard work.
- You see your classmate constantly looking at the clock in the classroom.
- You notice that a black bag has been left in the classroom as your classmates hurriedly walk out to their next class.
- You can’t find your cell phone anywhere.
- You hear a strange sound coming from the kitchen.
- You notice a woman with a large diamond necklace walk into the room.
- Your friend keeps yawning during a movie you’re watching together.
- You know that it’s a good idea to take a survival course before doing any hiking.