In a passive sentence, we sometimes mention the agent (the person or thing doing the action). We use by with the agent.
The cheque must be signed by the manager.
The medals were presented by Nelson Mandela.
But we mention the agent only if it is important for the meaning of the sentence. Sometimes we do not mention it.
1 We do not mention the agent if it does not add any new information.
All our money and passports were stolen. A man was arrested last night. We do not need to say that the money was stolen 'by a thief or that the man was arrested 'by the police'.
2 We do not mention the agent if it is not important.
The streets are cleaned every day. Oil has been discovered at the North Pole. Who discovered the oil is less important than the fact that it is there.
3 It is sometimes difficult to say who the agent is.
This kind of jacket is considered very fashionable these days.
A number of attempts have been made to find the Loch Ness monster.
B Empty subjects (they, people, etc)
Compare these two sentences.
ACTIVE
They clean the streets every day.
PASSIVE
The streets are cleaned every day.
The new and important information is how often the streets are cleaned. We are not interested in saying who cleans them. In the active sentence we can use the 'empty subject' they. We sometimes use a sentence with an empty subject instead of the passive, especially in conversation.
We can also use the empty subjects people, you, one and someone.
ACTIVE
People use this footpath all the time. You/One should check the details. Someone took my purse.
PASSIVE
This footpath is used all the time. The details should be checked. My purse was taken.
When do we use the passive?
We use the passive in both speech and writing, but it is more common in writing.
We see it especially in textbooks and reports. We use it to describe activities in industry,
science and technology, and also for official rules.
Bananas are exported to Europe. The liquid is heated to boiling point.
Payment can be made at any post office. Cars left here will be towed away. In these situations, it is often not important to say who is doing the action, or it is difficult to say.
The passive is also often used in news reports.
A number of political prisoners have been released. Talks will be held in London next week.
56 Exercises
i The passive and the agent (A)
Laura is writing to a friend. This is part of her letter.
Someone broke into our house at the weekend. The burglar took some jewellery. But luckily he didn't do any damage. A very nice young police officer interviewed me. Detectives found some fingerprints, and the police computer identified the burglar. Police have arrested a man and are questioning him. But they haven't found the jewellery.
Now complete the passive sentences in this conversation. Use a phrase with by only if it adds information.
Laura: Our house (►) was broken into at the weekend
Melanie: Oh no!
Laura: Some jewellery (1).............................................
But luckily no damage (2)...............................................
Melanie: Did the police come and see you?
Laura: Yes, they did. I (3) ..............................................................................
Melanie: I don't suppose they know who did it.
Laura: Well, amazingly they do. Some (4) ............................... ... ,
and the (5) ......................................................................................
A man (6)............................................................... and (7)
Melanie: Wonderful.
Laura: There's only one problem. The (8)
2 Active or passive sentence? (A)
The first motor car was made by a Belgian called Etienne Lenoir.
Write a paragraph from the notes about the first motor car. Some sentences are active and some are passive. Use a phrase with by only if it adds information.
► a Belgian called Etienne Lenoir / make / the first motor car
1. but / Lenoir / not produce / many cars / for sale But Lenoir
2. a German called Karl Benz / start / Commercial
Benz
commercial production
3 people / now / see / Benz / as the father / of the motor car
Empty subjects (B)
Reply to what people say. Use the suttject in brackets.
► Daniel: The bus fares have been increased, (they)
Vicky: What? You mean they've increased the bus fares again!
1 Melanie: Bicycles should be used for short journeys, (people) David: Yes, I agree.......................
2 Emma: A new source of energy has been discovered, (someone) Daniel: What? Did you say that.............................................................
3 Rachel: This building is going to be knocked down, (they) Vicky: Well, no one told me that ……………………………
4 David: Eggs shouldn't be kept in a freezer, (you)
Tom: Really? I didn't know......................................................................
5 Vicky: Why isn't litter put in the bin? (people)