The letters focus on many traditional themes of Stoic philosophy such as the contempt of death, the stout-heartedness of the sage, and virtue as the supreme good.

[8] Even if both writers had access to the imperial mail service, a letter from central Italy to Sicily would have taken four to eight days to travel.

[11] In letter 8, Seneca alludes to his retirement from public life, which is thought (by reference to Tacitus Annals xiv.

[12] Letter 91 refers to the great fire of Lugdunum (Lyon) that took place in the late summer of 64.

Although they deal with Seneca's personal style of Stoic philosophy, they also give valuable insights into daily life in ancient Rome.

The letters tend to open with an observation of a quotidian incident, which is then abstracted to a far wider exploration of an issue or principle.

[14] In letter 7, for instance, Seneca reports a chance visit to an arena gladiatorial combat, fought to the death; he then questions the morality and ethics of such a spectacle, in what is the first extant record of a pre-Christian writer expressing moral qualms on the matter.

[1] Underlying a large number of the letters is a concern with death on the one hand (a central topic of Stoic philosophy, and one embodied in Seneca's observation that we are "dying every day") and suicide on the other, a key consideration given Seneca's deteriorating political position and the Emperor's common use of forced suicide as a method of covert execution.

[18] The language and style of the letters is quite varied, and this reflects the fact that they are a mixture of private conversation and literary fiction.

[19] Seneca also uses a range of devices for particular effects, such as ironic parataxis, hypotactic periods, direct speech interventions and rhetorical techniques such as alliterations, chiasmus, polyptoton, paradoxes, antitheses, oxymoron, etymological figures and so forth.

Codex Quirinianus (or Brixiensis), Q, is a 9th or 10th century manuscript from the Biblioteca Queriniana, Brescia containing letters 1–120.12.

[24] The letters were a principal source for Justus Lipsius for the development of his Neostoicism towards the end of the 16th century.

Ducunt volentem fata, nolentem trahunt ('The fates lead the willing and drag the unwilling'), from Epistle 117 paragraph 11 line 5, expresses a fatalistic view of man's subjection to natural and divine will.