A quote by John Owen:
Tempora mutantur, nos et mutamur in illis.
I was wondering if you could tell me the difference between mutantur and mutamur?
Both are conjugated in the present tense, passive voice, and indicative mood, from the same verb: muto. The difference is that mutamur is conjugated in the 1st person (plural) (“we change”), while mutantur is conjugated in the 3rd person (plural) (“times change”).
Owen is quoting a well-known Latin adage meaning, “Times change, and we change with them.”
With respect to the passive voice being translated into English in the active voice—for example, “times change” rather than “times are changed”—Latin often declines verbs in the passive voice which are to be understood as intransitive. Of course, when translated into English, the intransitive verb is translated in the active voice without a direct object.
Ostium aperit homo.
The man opens the door.
Aperitur ostium ab homine.
The door is opened by the man.
The door opens. (literally, “The door is opened.”)
Therefore, we are not to understand mutamur as “we are changed”—truly passive as though some (unnamed) agent is changing us—but rather, the subject (“we”) is doing the action (change) to itself. In Koine Greek, this would be best demonstrated by the middle voice, but Latin lacks such a voice. Instead, it can use the passive voice without an object in the ablative. If the verb was to be understood as transitive, we would encounter an object declined in the ablative, indicating the agent (e.g., “[by] the man”) acting upon (e.g., “is opened”) the subject of the sentence (e.g., “the door”).