"Prefer the active voice."
That's the advice of the APA Style Manual (American Psychological Association [APA], 1994, p.32). Although the passive voice has certain uses, it is wordier and less direct than the active voice. Reserve its use for those times when it is appropriate.
Some students and teachers argue that they prefer the passive voice in scientific writing. I presume they believe that the passive voice is more "objective." True, the passive voice permits a writer to construct sentences without identifying their subjects, but obscuring the subject is not the same as being objective! Taken to its extreme, this practice promotes intellectual laziness, even dishonesty. Here's some advice from the professionals at:
Reference:
American Psychological Association. (1994). Expression of ideas. In Publication manual of the American Psychological Association. (4th ed.). Washington, DC: Author.
The passive voice is appropriate when:
- an action's object is more important than its subject:
"When they saw this, they made known what had been told them about this child; and all who heard it were amazed at what the shepherds told them."
Luke 2:17,18
"There was no hurry, for there was nowhere to go, nothing to buy and no money to buy it with, nothing to see outside the boundaries of Maycomb County. But it was a time of vague optimism for some of the people: Maycomb County had recently been told that it had nothing to fear but fear itself."
Harper Lee, To Kill a Mockingbird, 1960, p. 4.
- the subject of an action is unknown:
"...for he had seen the metal face of the age and had been so stunned by it that when he thought into the future, all he could vision was a world from which everything he counted important had been banished or had willingly fled."
Charles Frazier, Cold Mountain, 1997.
- the writer wishes to invert a sentence's order to place emphasis on its final words.