We should stop telling students and emerging writers that the passive voice is some sort of mortal sin in texts. It is not. Sometimes, the passive voice offers the best way to control what a reader perceives as important.
Consider the following reasons to use passive voice:
1. Technical manuals.
2. Aphorisms with no agent (actor) involved.
3. Unknown agent with the result more important than the action.
4. Action-focused sentences without a named agent.
Technical instructions are passive to focus on the object instead of the user of the object, often for legal compliance reasons.
Valve X is set to 150 degrees by the operator after ten minutes.
The software settings are found in the preferences menu.
The car should not be left in gear when parked.
The emphasis in technical manuals remains on the object of documentation: the valve, the application, the car.
“Universal Truth” or aphorism are often passive statements.
Rules are meant to be broken.
The universe is for exploring.
Any revision of that “truism” would be awkward, at best. “The people making rules mean for them to be broken.”
Unknown agents result in passive constructions. If you do not know who committed an action, it is appropriate to use passive voice.
My camera bag was stolen.
The bank was robbed.
The victim was beaten severely.
The thief is unknown in these examples, yet was the agent of action. Revising as “Someone stole my camera bag” shifts the focus to “someone” instead of the more important camera gear now missing.
Action-focused attention, or sentences meant to stress the object of the action are passive (and often the agent is omitted).
The family albums were burned in anger.
Revising this would be matter of style: “The stepson burned the family albums” might or might not convey the desired importance.