Active voice gives added strength to your statements by emphasizing the actor and allowing you to use more interesting verbs. It also reduces wordiness.
PASSIVE: The town was decimated by the earthquake.
In active voice, the sentence emphasizes the earthquake as the actor. Rephrasing also removes superfluous words.
ACTIVE: The earthquake decimated the town.
Passive voice can also make your statements vague, which causes them to have less impact:
PASSIVE: Mistakes were made.
Sentences like the one above make the writer seem either cowardly (doesn't want to admit who made the mistake) or ignorant (simply doesn't know who made the mistake), neither of which is a particularly good thing. Rephrase:
ACTIVE: We made mistakes.
This revised sentence is much clearer, and it will prevent readers from accusing the writer of being non-committal.
There are, of course, situations in which the use of passive voice is preferred:
- Certain types of science writing require passive voice because it is essential that the actor be entirely removed from the writing.
- When you need to emphasize the recipient of the action rather than the actor, passive voice is appropriate. For example, if in the following sentence you were writing to emphasize the widespread use of pesticides rather than the people who use them, you would use passive voice: Thousands of American fields are sprayed with harmful pesticides every day.