Metanoia (from the Greek μετάνοια, metanoia, changing one's mind) in the context of rhetoric is a device used to retract a statement just made, and then state it in a better way.[1] As such, metanoia is similar to correction. Metanoia is used in recalling a statement in two ways, either to weaken the prior declaration or to strengthen it.
Metanoia is later personified as a figure accompanying kairos, sometimes as a hag and sometimes as a young lady. Ausonius' epigrams describe her thus: "I am a goddess to whom even Cicero himself did not give a name. I am the goddess who exacts punishment for what has and has not been done, so that people regret it. Hence, my name is Metanoea."[2]
The use of metanoia to weaken a statement is effective because the original statement still stands, along with the qualifying statement.[3] For instance, when one says, "I will murder you. You shall be punished." the force of the original statement ("I will murder you") remains, while a more realistic alternative has been put forward ("you shall be punished").
When it is used to strengthen a statement, metanoia works to ease the reader from a moderate statement to a more radical one, as in this quote from Marcus Aurelius's Meditations
I still fall short of it through my own fault, and through not observing the admonitions of the gods, and, I may almost say, their direct instructions (Book One);[4]
Here Aurelius utilizes metanoia to move from a mild idea ("not observing the admonitions of the gods") to a more intense one ("not observing... their direct instructions"); the clause "I may almost say" introduces the metanoia.