Historia est Magistra Vitae (or often written like this, which is in a more Latin spirit - Historia magistra vitae est) is a Latin expression, taken from Cicero's De Oratore, which suggests that "history is life's teacher". The phrase conveys the idea that the study of the past should serve as a lesson to the future, and was an important pillar of classical, medieval and Renaissance historiography.
The complete phrase, with English translation, is:
Cicero, De Oratore, II, 36.
References
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