De Clementia (frequently translated as On Mercy in English) is a two volume (incomplete) hortatory essay written in AD 55-56 by Seneca the Younger, a Roman Stoic philosopher, to the emperor Nero in the first five years of his reign.
The Essay 
Seneca's De Clementia is an instructional contrast between the good ruler and the tyrant, and an evaluation of the relationship between ruler and subject. A survey of history is made in the first volume to select different rulers to point out as examples, including Dionysius of Syracuse and Sulla being used as cautionary tales and young Augustus as the exemplar. An extended illustration of Augustus showing mercy to the rebellious Cinna alongside an example from Nero's own life is meant to encourage the aspiring emperor to likewise show clemency.
While the first volume is accommodated to popular understanding the second book touches on stoic paradoxes and scholastic details. In general, the two books are not overly concerned with historical accuracy.
Within his essay, Seneca does not discuss the constitutional legitimacy of the principate, but rather deals with the problem of having a good sovereign. The only real power, in his view, was power which was guided by the Stoic conception of logos (universal reason). Thus, clemency, not pity or unmotivated generosity, is the reasonable approach which guarantees the consent and devotion of the emperor's subjects and provides the state's security.
Critical Reception 
Seneca's critical reception among near contemporaries in general was often severely criticized. Gellius states that his works as not particularly worth reading due to being pedestrian. Quintilian found his work admirable, but wasted with cheap effect and failing to demonstrate the possession of solid knowledge - in no way comparable to Cicero. In contrast to this, Seneca has seen extraordinary popularity in his own times and in the Renaissance.
|“||No creature is more fretful, or to be treated with greater skill, than man, and none should be treated with greater forbearance. - From Seneca.||”|
John Calvin's Commentary on De Clementia 
Shortly after finishing his legal studies, a young John Calvin wrote his first book, a commentary on De Clementia. The commentary consists mostly of philological notes and context with other Latin writers interspersed with notes on Seneca's style and ideas. There have been three suggested reasons for this. First, Erasmus wrote the preface to his 1529 translation of Seneca that he welcomed editorial comments by young scholars. In taking up this invitation, some believe Calvin was attempting to establish his reputation as a humanist among the intellectual elite. Second, because there was a general revival of Stoicism in Renaissance times, it may have been simply because Calvin wanted more popularity for Seneca, of whom his successor in Geneva, Theodore Beza, mentions was "a great favorite for him" because he was "obviously in accord with Calvin." The third possibility, generally rejected by scholars[who?], is that he was writing to the French King Francis I. The lack of a dedication to him, mention of him, and gross error that would have been made comparing Francis with Nero all lead to the theory's disuse.
In writing his Commentary, Calvin made use of the texts of two "ancient pillars," Cicero and Seneca, and two "modern pillars," Erasmus and Budaeus. Ford Lewis Battles argues there is a third "modern pillar," Phillipus Beroaldus the Elder. When quoting from sources, he is less versed in Greek literature than in Latin. It is worth noting that Calvin's brief biographical sketch of Seneca at the outset is taken almost entirely from Tacitus, while ignoring the less noble picture from Dio Cassius.
Fundamentally, Calvin at this point in his career is acting as a humanist and not a Protestant reformer. Calvin and Seneca agree that all men are sinners and sin needs to be punished, and both are committed to a deterministic theism. However, it becomes clear that Calvin had not intended to pass Stoic elements into Protestant theology, and in fact Calvin attacks the Stoic creed more often than he approves it. Beyond theological critique, Calvin also reproves Seneca's style as too luxuriant, and remarks, "I also miss the orderly arrangement of matter, which is certainly not the least quality of a good style." We can already begin to see the anticipation of Calvin's full development in his writing method and can expect the transformation of Calvin's classical learning and the seriousness of the Stoic ethic into Christian faith.
- James R. Harrison, Paul and the Imperial Authorities at Thessalonical and Rome, p.292
- Ford Lewis Battles, Sources of Calvin's Seneca Commentary, in Articles on Calvin and Calvinism, p.48
- Gian Conte, Latin Literature - A History, pp.412-413
- E. Vernon Arnold, Roman Stoicism, p.114
- John Davie, Seneca - Diologues and Essays Oxford University Press, 2007. ISBN 978-0-19-280714-4
- Luise Salley, A French Humanist's Chef-D'Oeuvre: The Commentaries on Seneca's "De Clementia" by John Calvin, in Articles on Calvin and Calvinism, p.75
- John Calvin, Tracts relating to the Reformation by John Calvin with His Life by Theodore Beza, vol.I, p.xxiv
- Luise Salley, A French Humanist's Chef-D'Oeuvre: The Commentaries on Seneca's "De Clementia" by John Calvin, in Articles on Calvin and Calvinism, p.76
- Ford Lewis Battles, Sources of Calvin's Seneca Commentary, p.52
- Luise Salley, A French Humanist's Chef-D'Oeuvre: The Commentaries on Seneca's "De Clementia" by John Calvin, p.76
- Luise Salley, A French Humanist's Chef-D'Oeuvre: The Commentaries on Seneca's "De Clementia" by John Calvin, in Articles on Calvin and Calvinism, p.82
- Edward F. Meylan, A Stoic Doctrine in Calvin, in The Romanic Review, pp.105-115
- John Calvin, Commentary on De Clementia, preface iii.
- Ford Lewis Battles, Sources of Calvin's Seneca Commentary, p.57