On the Firmness of the Wise) is a moral essay written by Seneca the Younger, a Roman Stoic philosopher, sometime around 55 AD.

The work celebrates the imperturbability of the ideal Stoic sage, who with an inner firmness, is strengthened by injury and adversity.

[2] The superior position the sage inhabits, of detachment from earthly future events of a detrimental nature, is the unifying theme of the dialogues.

The rest of the treatise through to chapter 19 consists of discussions on the nature of both themes, showing that the wise person is immune from both insults and injuries.

Seneca concludes the treatise praising the idea of the wise person while offering practical advice for all of us who are imperfect.