I came across a talk by Steven Pinker on “Linguistics, Style and Writing in the 21st Century.” The talk is excellent and covers several important areas of writing advice. One of them is the topic of active and passive voice. I was pleased to see Pinker give the same advice I have been teaching for a while: The adage “don’t use the passive voice” is nonsensical. Clearly, passive voice cannot be categorically the wrong choice. If it were, then why should it even exist in the English language? There must be a valid use for this grammatical construct. Pinker provides one, and I agree with him. Here I’ll present this perspective in my own words.
To fully understand when to use active or passive voice, we need to first grasp the concepts of the topic and the stress position. I have previously written a blog post about this topic. Please go ahead and read it now. I’ll wait.
Now that we’re all on the same page, let’s proceed. The simple rule is this: Topic and stress trump active and passive. If the topic is the actor, use active voice. If the topic is being acted upon, use passive voice. Examples:
Maria read a book.
The book was read by Maria.
The first is a story about Maria. The second is a story about a book.
As we construct a story, it is natural to move back and forth between active and passive while keeping the story focused on one protagonist:
John woke up with a splitting headache. Grudgingly, he got out of bed, brushed his teeth, and put on some clothes. As he walked down the stairs, he dreaded another boring day at the office. Yet, as he opened the door, he was greeted with the most amazing sight he’d ever seen.
Notice how everything is active voice until we reach “he was greeted” in the last sentence. This sentence needs to be in passive voice, so that John can remain in the topic position and “the most amazing sight he’d ever seen” takes on the stress position. Any attempt to use active voice here would result in a much weaker sentence.
Thus, it is best not to worry too much about active or passive voice. Instead, focus on telling a clear story by placing the the correct elements into the topic and stress positions of each sentence.
What’s the problem with passive voice, then?
If things are so simple, why do we keep hearing the advice to avoid passive voice? Because there are concrete issues that can arise when passive voice is used to excess, and I’ll briefly highlight the most important ones.
First, passive voice doesn’t convey action as strongly as active voice does. For example, consider these two sentences:
Thomas baked a cake.
The cake was baked.
The first evokes the image of a person being active in the kitchen, mixing ingredients together, putting serious effort into the creation of a cake. The second evokes the image of a cake sitting in the oven.
Second, passive voice makes it easy to hide the actor. For example, compare:
I made a mistake.
Mistakes were made.
The first clearly assigns blame, the second doesn’t. Some writers deliberately use passive voice to hide the actor.
In scientific writing, though, I think it’s more common that the actor is omitted not with ill intentions but merely due to a lack of writing skills, or maybe because of a false sense of modesty. The result, however, can be rather confusing. In particular, whenever I read an abstract written in the passive voice, I start to wonder whether the authors are providing background information from earlier work or telling me what they have done. For a recent example, consider the beginning of the abstract from this paper:
A fluorinated silyl functionalized zirconia was synthesized by the sol-gel method to fabricate an extremely durable superhydrophobic coating on cotton fabrics by simple immersion technique. The fabric surfaces firmly attached with the coating material through covalent bonding, possessed superhydrophobicity with high water contact angle ≈163 ± 1°, low hysteresis ≈3.5° and superoleophilicity. The coated fabrics were effective to separate oil/water mixture with a considerably high separation efficiency of 98.8 wt% through ordinary filtering. [. . .]
Finally, passive voice encourages complex sentences with low content-to-word ratio, with long prepositional phrases, and with nouns attempting to carry the action—in a word, the official style.
In summary, pay more attention to topic and stress positions than to active and passive voice. However, in case of doubt, choose active over passive constructs.