What Is Active Voice?

I'll start with active voice because it's simpler. In an active sentence, the subject is doing the action. A straightforward example is the sentence "Steve loves Amy." Steve is the subject, and he is doing the action: he loves Amy, the object of the sentence.

Another example is the title of the Marvin Gaye song "I Heard It through the Grapevine.” "I" is the subject, the one who is doing the action. "I" is hearing "it," the object of the sentence.

What Is Passive Voice?

In passive voice, the target of the action gets promoted to the subject position. Instead of saying, "Steve loves Amy," I would say, "Amy is loved by Steve." The subject of the sentence becomes Amy, but she isn't doing anything. Rather, she is just the recipient of Steve's love. The focus of the sentence has changed from Steve to Amy.

If you wanted to make the title of the Marvin Gaye song passive, you would say "It was heard by me through the grapevine,” not such a catchy title anymore.

Why Is Passive Voice Recommended for Science Writing?

An exception is that scientists are often encouraged to write in passive voice to lend their writing a sense of objectivity--to take themselves and their actions and opinions out of the experimental results. I used to be a scientist and I always found that odd. It felt as if we were trying to hide that real people did the experiments.

Some scientific style guides do allow for a limited use of active voice (1). For example, it may be OK to write, "We sequenced the DNA," instead of "The DNA was sequenced," but it's still considered bad for scientists to insert themselves into conclusions. For example, it would be bad scientific form to write "We believe the mutation causes cancer." But you still don't need passive voice to achieve your goals. For example, the active sentence "We believe the mutation causes cancer," could be changed to "The data suggests that the mutation causes cancer." That's still active, but it eliminates the sense of subjectivity.

Is Passive Voice OK in Crime Reports?

On the other hand, sometimes passive voice does have advantages. For example, if you truly don’t know who is taking the action, then you can’t name the person. This is especially common with crime reports. For example, a security guard might write "The store was robbed," because nobody knows who the robber was.