A.A. Long’s Reconstruction of the Diogenes Laertius Argument — Stoic Ethics as Entailed by Stoic Physics

 

A.A. Long’s Reconstruction of the Diogenes Laertius Argument — Stoic Ethics as Entailed by Stoic Physics

Theoretical foundations: Grant C. Sterling (Eastern Illinois University). Analysis and synthesis: Dave Kelly. Prose rendering: Claude (Anthropic). 2026.

---

Source

A.A. Long, “The Logical Basis of Stoic Ethics,” Proceedings of the Aristotelian Society, Vol. 71 (1970/71), pp. 85–104. The reconstructed argument appears at pp. 96–97, formalizing Diogenes Laertius VII 85–88.

---

Context

This is the argument Dave Kelly cited on the ISF in 2022 in an exchange with Nigel Glassborow over whether Epictetus’s ethics is “underwritten” by his theology (thread “rational faculty ~ prohairesis?,” February 2022, drawing at that time on Long’s later book Epictetus: A Stoic and Socratic Guide to Life, 2002). It is also directly relevant to Dave’s 2017 ISF thread “Does Marcus’ ethics depend on his physics?” (stoics@yahoogroups.com), where the list could not produce a formal derivation on request. Long’s 1971 article supplies that formal derivation, built from the earliest Stoic sources — Zeno, Cleanthes, Chrysippus — via Diogenes Laertius.

Long’s stated purpose in the article is to show that this derivation is not circular, against R.D. Hicks’s charge that Stoic ethics reduces to “it is reasonable to live according to nature and natural to live according to reason.” Long argues the direction of entailment runs one way: from Nature (physics) to reason and virtue (ethics), not the reverse.

---

The Argument

Long’s reconstruction, labeled as in the original:

• 1. (T) Nature creates all living things and provides them with the means of securing what is advantageous to them.
• 2. (S) That which accords with Nature is right.
• 3. Nature directs all animals (and children) by a self-protective impulse.
• 4. [From T + S] Therefore it is advantageous and right for all animals (and children) to be directed by their self-protective impulse.
• 5. (R) Nature directs all men to live by sound reason — self-protective impulse shaped by reason.
• 6. Therefore it is advantageous and right (accords with Nature) for all men to live by sound reason.
• 7. To live by sound reason = living in accord with human nature = living according to virtue.
• 8. Therefore it is advantageous and right for all men to live in accord with human nature and according to virtue. (Q1)
• 9. Human nature is part of Nature.
• 10. Therefore it is advantageous and right for all men to live in accord with human nature and Nature.
• 11. (P) To live in accord with Nature entails deliberate obedience to Nature’s will, which is living by sound reason.
• 12. Therefore it is advantageous and right for all men deliberately to obey Nature’s will. (Q2)

---

Long’s Gloss on the Direction of Entailment

Life according to reason is entailed by life according to Nature; but life according to Nature is not obligatory because it accords with reason. Nature stands to man as a moral law commanding him to live by rational principles.

(Long, p. 101)

---

Corpus Note

This is offered here as a documented primary/secondary source — an external scholar’s formal case for the orthodox (physics-grounds-ethics) reading of Stoicism. It does not itself bear on Sterling’s independent reconstruction, which proceeds without reliance on this derivation (see Does Science Recognize the Physics Ancient Stoic Ethics Was Connected To? and The Melding Question). Its corpus value is as reference material — the actual scholarly argument Dave has referred to across several ISF exchanges, now retrievable and cited precisely rather than from memory.

---

Theoretical foundations: Grant C. Sterling (Eastern Illinois University). Analysis and synthesis: Dave Kelly. Prose rendering: Claude (Anthropic). 2026.