Verbs in English are active or passive. Active verbs are much more common. Compare the following:
- Leonardo da Vinci painted the ‘Mona Lisa’. (active)
- The ‘Mona Lisa’ was painted by Leonardo da Vinci. (passive)
We use by before the person or thing that does the action, and with before the thing that is used by a person to do something:
- The class was taught by Mr Allen.
- He was struck by lightning.
- The rocks were broken up with a heavy hammer.
There are several reasons why we use the passive:
- to emphasize the object rather than the subject of a sentence: Playing cards were invented by the Chinese.
- when we don’t know who did something or when it isn’t important: The books were arranged in alphabetical order.
- when we don’t want to say who did something (e.g. to avoid blame): The doors were left unlocked all night.
- to sound more formal, for example in academic writing: The research was carried out by a team of researchers.
Passives can be formed with any tense and after modal verbs. You always need to use the past participle of the main verb:
- All the rooms are cleaned daily.
- Several mountain ranges can be seen from space.
- When I arrived, Harry was being beaten at chess by his six-year-old son.
- His relatives have been informed of his death.
- Everything we owned had been taken from us.