In Defense of Stoic Physics: A Response to Donald Robertson

The Core Issue

Donald Robertson's recent Substack article argues that Stoic ethics can function independently of Stoic physics (cosmology/theology). He claims that ethics follow from logic rather than physics, making Stoicism accessible to modern atheists and agnostics without requiring commitment to Stoic theology.

This position has significant implications for how we teach and practice Stoicism, particularly within institutions like the College of Stoic Philosophers, which Robertson explicitly criticizes for insisting on the connection between physics and ethics.

The Derivation Problem

Robertson's fundamental error is conflating the structure of Stoic philosophy with the derivation of its conclusions. He correctly identifies that Stoicism comprises three branches - physics, logic, and ethics - but fails to explain how ethical conclusions are actually generated.

Logic as Method, Not Source

Logic in Stoicism is the method of derivation, not the source of content. It functions as the inference process that connects premises to conclusions:

IF [Stoic physics: rational cosmos, humans as parts of divine rational whole]
THEN [via logical reasoning]
Stoic ethics: virtue as sole good, living for the benefit of the whole

Robertson's argument removes the IF clause while keeping the THEN clause. He's left with "THEREFORE virtue is the sole good" - but therefore what? Logic requires premises to operate on. You cannot derive conclusions from the method of reasoning alone, any more than you can use mathematics to generate numbers ex nihilo.

The Missing Premises

Robertson asserts that "excellence in reasoning is our good" follows from recognizing reason as our essential nature. But this claim raises immediate questions:

1. Why does "reason is our nature" lead to Stoic virtue ethics specifically, rather than Epicurean ethics, utilitarian calculation, Aristotelian mean-based ethics, or any other rational system?

2. Why is virtue the sole good rather than one good among many?

3. Why does living according to reason mean living for the benefit of the whole?

4. Why these four cardinal virtues (wisdom, justice, courage, temperance) rather than others?

These are specific Stoic conclusions that require specific premises. In traditional Stoicism, those premises come from physics - understanding ourselves as parts of a rational, interconnected, providentially-ordered cosmos. Remove that metaphysical foundation and these conclusions become arbitrary assertions rather than logical derivations.

The Grounding Question

"Living according to Nature" as an ethical formula only works if Nature has particular characteristics. The Stoics didn't mean "do what comes naturally" in the sense of following impulses. They meant aligning yourself with the rational structure of the cosmos - the logos that pervades and orders all things.

Without Stoic physics, this reduces to "live according to reason," which is:

• Much thinner as a principle
• Shared by many philosophical systems
• Incapable of generating the specific conclusions Stoicism is known for

We might ask: without the physics, what distinguishes Stoic ethics from general virtue ethics, secular humanism, or rational egoism? What makes it specifically Stoic?

The answer is that Stoic ethics are derived from understanding our relationship to the cosmos. We should act for the benefit of the whole because we are parts of that whole, and the whole is rationally ordered. Our individual good and the cosmic good align because we participate in the same divine reason.

Strip away the physics and you lose this derivation entirely. You're left with deontological duties floating in a metaphysical vacuum.

The Aristo Objection

Robertson cites Aristo of Chios as evidence that Stoic ethics can function independently of physics. This is deeply misleading.

Aristo was explicitly criticized by other Stoics for neglecting physics and logic in favor of focusing solely on ethics. He was considered heterodox within the school - an outlier who departed from orthodox Stoic teaching. Diogenes Laertius records that Aristo "did away with logic and physics" and that other Stoics regarded this as a fundamental error.

Using Aristo as evidence for how mainstream Stoicism works is like citing a fringe Protestant sect to explain Catholic doctrine. The fact that one member of a philosophical school took an unusual position doesn't make that position representative of the school's teaching.

The Marcus Aurelius Misreading

Modern Stoics repeatedly cite the "providence or atoms" passages from Marcus Aurelius's Meditations as evidence that Stoic ethics don't depend on Stoic physics. This represents a fundamental misreading of Marcus's rhetorical technique.

The Passages

The commonly cited passages include:

• Meditations 9.28: "If all is God, then all is well. But if ruled by chance, don't you too be ruled by chance."

• Meditations 12.14: "Consider yourself fortunate if in the midst of such a whirlwind you possess a guiding intelligence within yourself."

The Context

These passages don't express metaphysical agnosticism. Marcus is employing a common philosophical technique - arguing from the weakest position to demonstrate the robustness of his conclusions.¹

The Epicurean model (atoms, chance, indifferent gods) was a competing framework. By saying "even if the Epicurean view were correct, virtue would still matter," Marcus strengthens his argument. He's showing that Stoic ethics are rationally compelling even under the most skeptical assumptions about cosmic order.

But we know from the entirety of the Meditations that Marcus believed in providence and divine reason. The work is saturated with references to Zeus, the logos, universal nature, and rational cosmic order.

The Real Significance

Pierre Hadot's analysis in The Inner Citadel notes that Marcus consistently returns to the Stoic framework after these rhetorical explorations. He's not expressing doubt - he's demonstrating philosophical rigor by stress-testing his beliefs against the strongest alternative.

Ironically, this actually supports the traditional position: Marcus felt compelled to address the Epicurean physical model precisely because he understood that different metaphysics generate different ethical frameworks. He wasn't saying "physics doesn't matter" - he was showing that even with the wrong physics, virtue would still be a rational choice. But he clearly believed the Stoic physics were correct.

Why This Keeps Getting Cited

Modern Stoics rely heavily on Aristo and the Marcus passages because they don't have much else to work with. If Stoic ethics truly functioned independently of physics throughout the tradition, we would expect abundant examples across Stoic literature. Instead, we have:

• One heterodox figure (Aristo) who was criticized by other Stoics
• One rhetorical device in Marcus that's been persistently misread
• The vast majority of Stoic texts treating physics as foundational

From Chrysippus through Epictetus, mainstream Stoicism consistently derives ethics from physics. Citing the outliers doesn't overturn the tradition.

The Retrofit Problem

Both modern Stoicism and historical deism engage in similar projects: retrofitting Christian ethical intuitions with alternative metaphysical foundations.

Deists said: "We'll keep the Christian God but strip away revelation, miracles, and institutional church - anything that can't be justified by reason alone."

Modern Stoics say: "We'll keep Christian-compatible ethics (virtue, duty, self-control, cosmopolitanism) but strip away theological grounding entirely."

Both movements work backward from ethics they already accept culturally, then shop for metaphysical foundations that are just enough to support those ethics while avoiding what they find objectionable.

The problem is that both approaches are parasitic on Christian culture. They're not deriving ethics from first principles - they're preserving familiar ethics while swapping out foundations. This is intellectually dishonest.

Traditional Stoicism didn't start with Christian ethics as baggage. It derived its ethics from its understanding of cosmic nature and human nature as participations in divine reason. A genuinely fresh start from Stoic metaphysics might lead to ethics quite different from what modern Westerners take for granted.

The Accessibility Argument

Robertson expresses concern that Stoic physics "puts off" modern audiences who are uncomfortable with religious or theological frameworks. This is a practical consideration about accessibility, not a philosophical argument about what Stoicism actually teaches.

The question for educators and practitioners isn't what's most palatable to contemporary sensibilities, but what's accurate to the Stoic system. If Stoic ethics genuinely require Stoic physics for their derivation, then attempting to separate them produces something that isn't actually Stoicism - it's a modern invention wearing Stoic vocabulary.

Furthermore, the assumption that modern audiences are put off by "religion" often conflates Stoic theology with Judeo-Christian-Islamic theism. Stoic physics is not:

• Belief in a personal God who issues commandments
• Acceptance of divine revelation or scripture
• Membership in an institutional church
• Faith in miracles or supernatural intervention

Stoic theology is rationalist metaphysics - the claim that reality has a rational structure that can be understood through reason and observation. This is quite different from what modern atheists are reacting against when they reject "religion."

The Commercial Imperative

There's an elephant in the room that needs addressing: it is impossible for anyone who categorically disavows the possibility of religion, God, or providence to ever accept Stoic physics. For such individuals, Stoic theology isn't just false - it's unacceptable as a category.

The only way to continue marketing Stoicism to modern atheists and agnostics is to discredit or marginalize Stoic physics. This isn't primarily a philosophical move - it's a commercial one. Modern Stoicism has become a profitable industry of books, podcasts, conferences, apps, and merchandise. The brand has value. "Stoicism" sounds serious, ancient, philosophical - it has cultural cachet that "secular virtue ethics" or "rational self-improvement" lacks.

But there's a fundamental dishonesty in continuing to use the term "Stoicism" - even qualified as "modern Stoicism" - when what's being taught is incompatible with the philosophical system that existed in ancient Greece and Rome. If the physics are truly dispensable, if the theological framework is merely historical baggage, then what's being taught isn't Stoicism. It's something else that borrows Stoic vocabulary and aesthetic.

The honest move would be to name it something different rather than co-opting a term with two millennia of specific philosophical meaning. Call it "rational virtue ethics," "philosophical resilience," "practical wisdom traditions" - anything that doesn't claim continuity with a tradition whose core metaphysical commitments are being explicitly rejected.

But that would sacrifice the brand. "Stoicism" sells. It's chic. It has a certain masculine, martial appeal in contemporary culture. You can sell challenge coins, journal prompts, and conference tickets under the Stoic banner in ways you couldn't with a more honest descriptor.

This creates perverse incentives. The more successful modern Stoicism becomes as a commercial enterprise, the stronger the pressure to maintain the brand while diluting the content. And the more necessary it becomes to discredit traditional Stoicism - to paint figures like Chris Fischer and institutions like the College of Stoic Philosophers as gatekeepers peddling unnecessary theology, making Stoicism "inaccessible" to modern audiences.

The irony is that this commercialized version of Stoicism undermines its own foundations. If Stoic ethics truly are just common-sense virtue ethics that any rational person would arrive at independently, why do you need the Stoic brand at all? Why not just teach virtue ethics on their own merits?

The answer is that the ancient Stoics weren't selling self-help. They were offering a complete philosophical system that explained the nature of reality, how humans fit into that reality, and therefore how we should live. The ethics followed from the metaphysics. Remove the metaphysics and you're left with ethical assertions that may be appealing but aren't distinctively Stoic.

Questions for Reflection

Those who argue that Stoic ethics can stand independently of Stoic physics must answer:

1. What are the premises? If ethics follow from logic rather than physics, what premises is logic operating on? Where do those premises come from?

2. Why these specific ethics? What generates the distinctively Stoic conclusions (virtue as sole good, cosmopolitanism, living for the whole) rather than other possible ethical systems?

3. What makes it Stoic? Without the metaphysical framework, what distinguishes this from general virtue ethics, secular humanism, or rational self-help?

4. Why the traditional formula? "Living according to Nature" only makes sense as an ethical principle if Nature has specific characteristics. What does this phrase mean without Stoic physics?

5. Where's the historical support? If this separation were valid, why do we find so few examples in ancient Stoic literature of ethics being taught independently of physics?

6. Why keep the name? If Stoic physics are dispensable, what makes this "Stoicism" rather than something else using Stoic vocabulary?

Conclusion

Robertson's article provides academic cover for a trend already underway in modern Stoicism - the gradual abandonment of Stoic metaphysics while preserving Stoic-flavored ethics. But this project rests on a logical error: mistaking the structure of philosophy for the derivation of conclusions.

Logic is a method, not a source. It connects premises to conclusions but cannot generate conclusions without premises. Stoic physics provides those premises. Remove them and you're left with ethical assertions that may be appealing or useful, but aren't actually derived from anything.

The question isn't whether we can practice Stoic-like ethics without believing Stoic theology. Obviously we can - people do it all the time. The question is whether that practice is genuinely Stoicism or something else using Stoic vocabulary.

If we're serious about teaching and practicing Stoicism rather than modern self-help dressed in ancient language, we need to grapple honestly with the metaphysical foundations that make Stoic ethics what they are. That may be less accessible to modern audiences, and it certainly won't sell as many books or conference tickets. But it's intellectually honest.

The alternative is to admit we're not actually teaching Stoicism - we're teaching whatever ethics we find useful while borrowing Stoic branding for cultural legitimacy.

This document represents one perspective in an ongoing conversation within the Stoic community about the relationship between physics, logic, and ethics. It's written in response to Donald Robertson's article but isn't intended as a personal attack - rather, as a defense of traditional Stoicism's integrated philosophical system against recent attempts to fragmentize it.