The Invention of Duty: Stoicism as Deontology


Did the ancient Greeks and Romans have a concept of moral duty? Jack Visnjic seeks to settle this long-standing controversy in The Invention of Duty: Stoicism as Deontology. According to the prevailing view, ancient ethical systems lacked any sense of moral obligation and were built instead around notions of virtue and human flourishing. Visnjic argues that, millennia before Kant, the Stoics already developed a robust notion of moral duty as well as a sophisticated deontological ethics. While most writings of the Stoics perished, their concept of duty lived on and eventually came to influence the modern notion. In fact, there are strong indications that Kant’s formulation of a new duty-based morality was inspired by his encounter with Stoic ideas.

"I found Visnjic’s account of Stoic ethics rich and stimulating [...]. I am now converted to the view that one ought to think of Stoic kathêkonta as duties rather than merely appropriate courses of action and I am grateful to Visnjic for pushing this point."
-John Sellars, Royal Holloway, University of London, Bryn Mawr Classical Review (July 2021)

Prices from (excl. shipping):

Add to Cart
Jack Visnjic, Ph.D. (2018), Princeton University, is Director of Research at the Anacyclosis Institute and creator of the popular podcast Ancient Greece Declassified. Through his work, he strives to make the classics accessible and relevant to a broad audience.
Note to the Reader


1 The Birth of a Concept
 1 How to Say “Duty” in Ancient Greek
 2 The Original Meaning of Kathêkon
 3 Activities Prescribed by Nature
 4 Zeno’s “Etymology” of Kathêkon
 5 Final Remarks about Translating Kathêkon

2 Rules Are for Fools
 1 The Nature of the Evidence
 2 Are Kathêkonta Rules?
 3 The Disturbing Theses
 4 Duties in Dire Circumstances
 5 How Duties Change
 6 Variations of the No-Rules Interpretation
 7 Reconstructing the Typology of Kathêkonta
 8 Conclusion

3 A Formula for Action
 1 In Search of a Stoic Method of Deliberation
 2 Cicero’s Formula
 3 Seneca’s Formula
 4 What about Epictetus and Marcus Aurelius?
 5 Conclusion

4 Discovering Duty
 1 The Deliberator’s Toolkit: Kanones and Regulae
 2 Where Does the Formula Come In?
 3 Taking Guidance from Roles
 4 How Roles, Regulae, and the Formula Work Together
 5 Conclusion

5 Kant and the Stoics
 1 On the Various Approaches to Studying Kant’s Stoic Influences
 2 How Much Ancient Philosophy Did Kant Know?
 3 Kant and the Stoics on the Will and Practical Reason
 4 Kant and the Stoics on Happiness
 5 Conclusion

6 Kant and Kathêkon
 1 Two Types of Dutiful Actions
 2 Maxims vs. Dogmata
 3 The Categorical Imperative
 4 The Formula of Humanity
 5 Conclusion

Appendix 1: Determining the Meaning of Kathêkon
Appendix 2: New Translations of Key Passages
All interested in the history of ideas, ancient Greek and Roman philosophy, moral philosophy, Stoicism, or the philosophy of Kant; and anyone interested in the foundations of morality and the history of the concept of duty.
  • Collapse
  • Expand