9.Tacitus, Annals 15.62.
10.This line from Socrates was a favorite among the Roman Stoics. Epictetus quotes it at the end of his “manual” or “handbook”; see Epictetus, Handbook 53.4. Another Roman senator, Thrasea Paetus, who was also a Stoic and put to death by Nero, is reported to have said, “Nero can kill me, but he cannot harm me.” See Emily Wilson, The Greatest Empire, 154.
11.Seneca, Letters 123.6.
12.Seneca, Letters 122.14.
13.Seneca, Letters 115.9.
14.As Brad Inwood has noted, Seneca was “an original and innovative exponent” of Stoic philosophy, “one whose distinctive contribution seems to be a sensitivity to the value of first-hand experience in ethics and moral psychology.” Inwood, Reading Seneca: Stoic Philosophy at Rome (Oxford: Clarendon Press, 2005), 3.
CHAPTER 1: THE LOST ART OF FRIENDSHIP
1.Seneca, Letters 48.2–3. Seneca also wrote a work On Friendship, of which only short fragments survive. On the topic of friendship in Seneca, with plentiful quotations, see Anna Lydia Motto and John R. Clark, “Seneca on Friendship,” Atena e Roma 38 (1993): 91–96.
2.Seneca, Letters 106.12.
3.According to the Stoic Aristo, quoted by Seneca in Letters 94.16, unless someone has a medical disease, all “madness” or mental suffering originates from holding false opinions. Seneca agreed with this view. In On the Tranquility of Mind, Seneca is approached by his friend Serenus, as though Seneca is a doctor. Serenus, the patient, explains his mental suffering, and Seneca responds as a philosophical therapist to cure the condition. For a letter that strongly resembles a cognitive therapy session between Lucilius and Seneca, see Letters 24. Lucilius is anxious because he has been named the target of a lawsuit; Seneca aims to help Lucilius overcome his anxiety by using a step-by-step therapeutic approach.
4.Seneca, Letters 40.1.
5.Seneca, Letters 9.12. According to Cicero, the Stoics believed that friendship should be pursued for its intrinsic value, not for what you could get out of a friendship in a utilitarian way (Cicero, On Ends 3.70).
6.See John M. Cooper, “Aristotle on the Forms of Friendship,” The Review of Metaphysics 30, no. 4 (1977): 648.
7.See Nancy Sherman, “Aristotle on Friendship and the Shared Life,” Philosophical and Phenomenological Research 47, no. 4 (1987): 610.
8.Seneca, Letters 6.1.
9.Seneca, Letters 6.1.
10.A summary of Plato, Symposium 203E–204A.
11.Diogenes Laertius, Lives of the Eminent Philosophers 6.54.
12.For the evidence, see John Sellars, The Art of Living: The Stoics on the Nature and Function of Philosophy (London: Bristol Classical Press, 2009), 59–64.
13.For more on the extreme dichotomy between the sage and non-sages, see John Sellars, The Art of Living, 59–64; Sellars, Stoicism (London: Routledge, 2014), 36–41; and Tad Brennan, The Stoic Life: Emotion, Duties, and Fate (Oxford: Oxford University Press, 2005), chapter 4. The modern philosopher Lawrence C. Becker also rejected the early Stoic idea that virtue was an all-or-nothing matter, along with the strict dividing line between sages and nonsages, as being “untenable.” See Becker, A Modern Stoicism, 2nd ed. (Princeton: Princeton University Press, 2017), 132–33 and following.
14.Introduction to Seneca, Letters on Ethics to Lucilius, translated by Margaret Graver and A. A. Long (Chicago: University of Chicago Press, 2015), xx.
15.Evidence suggests that Zeno, the founder of Stoicism, also identified Socrates as being a sage. See René Brouwer, The Stoic Sage: The Early Stoics on Wisdom, Sagehood and Socrates (Cambridge: Cambridge University Press, 2014), 109, 164.
16.Emily Wilson, The Greatest Empire: A Life of Seneca (New York: Oxford University Press, 2014), 146.
17.Seneca, Letters 57.3.
18.Seneca, Letters 71.36.
19.On what Marcus Aurelius was trying to accomplish in the Meditations, see John Sellars, Marcus Aurelius (London: Routledge, 2021), 20–36. As William O. Stephens and others have pointed out, a better title for the Meditations of Marcus Aurelius might be “Memoranda,” since it consists of notes to himself about Stoic principles to remember on a daily basis. Stephens, Marcus Aurelius (New York: Continuum, 2012), 2.
20.Seneca, On Anger 3.36.3–4.
CHAPTER 2: VALUE YOUR TIME: DON’T POSTPONE LIVING
1.Seneca, Letters 1.1.
2.Seneca, Letters 1.2.
3.Seneca, Natural Questions, preface 1.2.
4.Seneca, On the Shortness of Life 2.1 and 1.3.
5.Seneca, On the Shortness of Life 2.1–2.2.
6.Seneca, Letters 3.5.
7.Seneca, Letters 106.1 and 22.8.
8.Seneca, On Tranquility of Mind, 12.2–3.
9.Seneca, On the Shortness of Life 3.5.
10.Zeno, cited by Diogenes Laertius, Lives of the Eminent Philosophers 7.121–22.
11.On the Stoic metaphors of slavery and freedom, see the introduction by A. A. Long to Epictetus, How to Be Free: An Ancient Guide to the Stoic Life (Princeton: Princeton University Press, 2018). For the use of these metaphors in Seneca, see Catharine Edwards, “Free Yourself! Slavery, Freedom, and the Self in Seneca’s Letters,” in Seneca and the Self, eds. S. Bartsch and D. Wray (Cambridge: Cambridge University Press, 2009), 139–59.
12.Seneca, Letters 22.11.
13.Epictetus, Discourses 2.1.22.
14.Epictetus, Discourses 4.1.113.
15.Seneca, On the Shortness of Life 9.1.
16.Seneca, On the Shortness of Life 14.1.
17.Seneca, On the Shortness of Life 14.1–2. For more on Seneca’s idea of a timeless community of wise people, see the conclusion to Catharine Edwards, “Absent Presence in Seneca’s Epistles: Philosophy and Friendship,” in The Cambridge Companion to Seneca, eds. Shadi Bartsch and Allesandro Schiessaro (New York: Cambridge University Press, 2015), 41–53.
18.Seneca, On the Shortness of Life 15.2.
19.Seneca, Letters 62.2. In his lost work On Marriage, of which only fragments survive, Seneca said that a wise person will never feel lonely because he or she will have so many friends from the past. See Liz Gloyn, The Ethics of the Family in Seneca (Cambridge: Cambridge University Press, 2017), 222.
20.Seneca, On the Shortness of Life 15.5–16.1.
CHAPTER 3: HOW TO OVERCOME WORRY AND ANXIETY
1.Seneca, Letters 5.8.
2.Marcus Aurelius, Meditations 4.7.
3.Seneca, Letters 101.8.
4.Marcus Aurelius, Meditations 12.26. On Marcus Aurelius reading Seneca, see John Sellars, Marcus Aurelius (London: Routledge, 2021), 12.
5.Paraphrase of Seneca, Letters 89.1.