Strunk and White’s highly respected The Elements of Style is prejudiced. The authors prefer, strongly, the use of active voice in English prose. As they put it: “Use the active voice.” The active voice is “more direct and vigorous than the passive.” Many of their readers seem to stop at this sentence and go on to torture their students with the proscription “never to use the passive voice.” But even The Elements of Style sees a place for the passive voice, “which is frequently convenient and sometimes necessary” (page 18).
I generally have the same bias—given the choice, I will elect active voice. However, I think “sometimes necessary” is an understatement that belies prejudice. We do a disservice when we ask students to eliminate the passive voice from their writing. Instead, we ought to ask them to consider its efficacy whenever they revise.
Let me provide a quick review of passive voice. In active voice, the grammatical subject of the sentence performs the action expressed in the grammatical predicate:
The meta-analysis (Hillocks 1984) concluded that de-contextualized lessons in grammar do not improve writing quality significantly.
The action is “concluded” and the “study” does the concluding. Sometimes writers confuse this form of active voice with passive. They consider it “passive” because people are not mentioned. Other ways to write this sentence in active voice would be:
Hillocks (1984) performed a meta-analysis and concluded that de-contextualized lessons in grammar do not improve writing quality significantly.
Hillocks’ meta-analysis (1984) concluded that de-contextualized lessons in grammar do not improve writing quality significantly.
De-contextualized lessons in grammar do not improve writing quality significantly (Hillocks 1984).
The same ideas expressed in passive voice would look like this:
It was found that de-contextualized lessons in grammar do not improve writing quality significantly (Hillocks 1984).
It was concluded by Hillocks (1984) that de-contextualized lessons in grammar do not improve writing quality significantly.
De-contextualized lessons in grammar were not found to improve writing quality significantly (Hillocks 1984).
Each version serves a slightly different purpose, and selecting the “correct” one depends on which fits best with the surrounding sentences, the emphasis, the meaning, and the rhythm of the prose.
Sometimes active is best when you want to emphasize the actor, say Hillocks; and passive often makes the object being acted upon, de-contenualized lessons in grammar in this case, the focus. But as these examples show, the choice can be a bit more complicated, so insisting student writers stick to either one or the other may not be productive.
For an excellent and more extended discussion of the passive and active voice in science writing, see Robert Goldbort’s Writing for Science, Yale University Press, 2006.