Tacitus (c. A.D. 55 - c. A.D. 120) was himself a Roman senator; his writing shows a particular interest in the conduct of senators. Prior to Tacitus’ time, Rome had been a republic (509-27 B.C.).

As Tacitus explores, the Roman senate declined from a long-held position of authority under the Roman Republic to become a body almost wholly reliant on the whims of a given emperor.

On the emperor Galba, who ruled for about 20 minutes, Tacitus described him succinctly: capax imperii, nisi imperasset. People would have believed him capable of ruling, if he hadn’t ruled.