De Constantia

Justus Lipsius's 1584 dialogue arguing for Stoic constancy as the response to the political chaos of the religious wars — the 'constant man' maintains inner stability regardless of external turmoil — which launched the Neo-Stoic movement of the late 16th and 17th centuries.

Revived Stoicism as a practical philosophy for political and personal crisis — making the argument that constancy of mind is the only adequate response to a world of violent religious conflict — and providing the philosophical framework that would influence Shakespeare, Montaigne, and the entire early modern period.