The Connection Between Physics and Ethics
Stoic ethics is interdependent with a specific model of the cosmos. The Stoics rejected and argued stridently against the random, meaningless universe of the Epicureans. In contrast, the Stoics built their philosophy around a rational, intelligent, and providentially ordered cosmos. They considered this worldview essential to their systematic philosophy because it provides the necessary framework for Stoic ethical theory and practice.
There are numerous outstanding expositions of Stoic ethical theory. Since I am not defending Stoic ethical theory, I will not delve into details. Nevertheless, an overview is helpful, and Tad Brennan offers an accessible and brief introduction to Stoic ethics:
To begin with, the Stoics assume that all human beings wish to be happy, and that happiness is our end, that is, that for the sake of which we do everything we do. They also tell us what happiness is: it consists in following nature. To follow nature means to act in accordance with our own nature as human beings, but also to act in accordance with Nature as a whole, that is, the entire cosmic order governed by Zeus. By following nature, we will be happy. By following nature, we will also be virtuous.
A.A. Long summarizes the Stoic philosophical system and highlights the connection between its physics and ethics in Hellenistic Philosophy; Stoics, Epicureans, Sceptics. An outline of his thought follows:
• The Stoics “prided themselves” on the coherence of their philosophical system
• They believe the universe is “amenable to rational explanation” because it is “rationally organized.”
• Mankind derives their rationality from the same logos embodied in the universe.
• Cosmic and human events are consequences of the same logos.
• Mankind is related to cosmic Nature or God through the rationality of the logos.
• Full recognition of the implications of our relationship to cosmic Nature will inspire us to live up to the excellence of our human potential by living in agreement with cosmic Nature.
• Natural philosophy (science) and logic are tools that enable mankind to know what facts are true.
• “The coherence of Stoicism is based upon the belief that natural events are so causally related to one another that on them a set of propositions can be supported which will enable a man to plan a life wholly at one with Nature or God.”
While scholars agree there is a connection between physics and ethics in Stoicism, a modern debate has split scholars into two groups. On one side, the “orthodox” scholars consider physics foundational to Stoic ethics, which makes the relationship between them hierarchical. On the other side, “heterodox” scholars see the relationship as interdependent or mutually supporting rather than hierarchical. It is important to understand that this debate is over the nature of the relationship between Stoic physics and ethics, not about whether a relationship exists at all. Scholars agree; a relationship exists between physics and ethics in Stoicism.
The Modern Debate
Julia Annas’s book The Morality of Happiness (1993) triggered a debate among scholars about the nature of the relationship between physics and ethics in Stoicism. Annas challenged the orthodox view, held by a majority of scholars, which suggests cosmic nature (physics and theology) provides the foundation for Stoic ethics. Several scholars responded to Annas. John Cooper provided a response in 1995. Annas countered in the same periodical. More than twenty years later, a majority of scholars still hold to the orthodox view that physics is foundational to Stoic ethics. Nevertheless, Annas’ critique prompted clarification on both sides of the debate. Annas argues that cosmic nature does not add new content or motivation to the ethical ideal of living according to virtue. While Annas never argued for the removal of cosmic nature from Stoicism, her original articulation in 1993 led some to believe it can be abandoned entirely without affecting Stoic ethics. Even Annas considered whether her position trivialized the role of physics in Stoics ethics. After arguing,
Nature in Stoic theory is not a non-ethical foundation for ethics, a physical and theological notion from which ethics is derived. Nature as that is relevant to ethics—the determination of our final end—is human nature… Human nature is part of cosmic nature, but in doing ethics, as opposed to studying the role of ethics in physics and theology, cosmic nature does not determine ethical theses. And even human nature is not an independent foundation for virtue; virtue and nature are interdependent elements in an overall theory.
If this is so, however, have we not gone too far to the other extreme, and given nature too trivial a role in ethics?
Many scholars do believe she went too far. Thus, it is interesting to see Annas’ rearticulated position more than a decade later. In 2007, she wrote,
Becoming a good Stoic requires more, however, than mastering the ethical part. Stoic philosophy consists of all three parts strongly unified into a whole.
She further adds,
The person who has studied ethics, then, needs to go on not only to study the other two parts but to integrate their results with ethics to produce a unified understanding from all three perspectives.
Finally, Annas acknowledges the psychological effect of integrating cosmic nature into Stoic ethics,
These ethically transformative conclusions are indeed strengthened when they are seen not independently, but in the context of and integrated with physical conclusions about Providence and the rational ordering of the world. Thus ethics is better understood and more stable in the agent’s psychology when integrated with physical conclusions about Providence.
Today, scholars are still divided between these two positions. Marcelo Boeri labels the opposing sides as orthodox and heterodox while Tad Brennan refers to them as naturalistic (which emphasizes the role of metaphysics, cosmology, theology, and anthropology) and rationalistic (which emphasizes the role of reason, rational consistency, rules, and considerations of autonomy). Again, scholars agree there is a relationship between physics (cosmic nature) and ethics in Stoicism; the disagreement is over the exact nature of the relationship between them. Boeri summarizes the debates as follows:
In recent years there has been a debate concerning whether or not Stoic ethics does depend on claims about cosmic nature. Some scholars have defended the thesis that Stoic ethics should be considered free from cosmic nature (and, therefore, as not dependent on providential cosmology; I shall call this interpretation ‘the heterodox view’). Others have argued heavily for the respectability and reasonableness of the cosmic viewpoint in Stoic ethics (I shall call this position ‘the orthodox view’).
Boeri goes on to explain why he prefers the orthodox view,
For the reasons I will be giving in what follows I tend to believe that the [orthodox] view is the correct one, not only due to the overwhelming number of texts where it is explicitly stated that cosmic nature should be taken into account, but also because of Stoic philosophical ‘holism’. Such a ‘holistic’ conception of philosophy takes for granted that all the parts of philosophy (ethics, physics, and logic) are so interrelated with each other that, to some extent, no part can be considered independently of the others.
Christopher Gill, in his recently published translation and commentary on the Meditations of Marcus Aurelius, offers a well-reasoned, and balanced position on the connection between physics and ethics. He writes,
My own view on this topic is that, while Stoicism aspired to combine all three branches of knowledge, this combination is typically conceived as reciprocal and non-hierarchical. The underlying thought is that the best available accounts of ethics and physics (and logic, as Stoics understand this branch of philosophy) are compatible and mutually supporting.
Gill does not appear to fall squarely into either the orthodox or the heterodox group. He argues strongly for the influence of Stoic physics on ethics; yet, he does not agree the relationship between them is foundational (hierarchical). In his introduction to the Robin Hard translation of the Meditations, Gill writes,
The Stoic belief in inbuilt purpose was connected with their view that all events are determined, and that the whole sequence of events embodies divine purpose or providentiality. As this point illustrates, the Stoics saw the branches of philosophy (in this case, ethics and physics) as interconnected and mutually supporting. Thus, their belief in divine providence belonged to the study of theology (which for them formed part of physics). But this belief also helped to provide a meaningful framework for ethics; while ethics in turn made sense of ideas (such as ‘good’) which underpinned the notion of providentiality and thus supported the principles of theology. As this point indicates, the Stoics saw philosophy as forming a highly unified and systematic body of knowledge. The ability to trace and understand connections between different ideas and between the branches of philosophy thus formed an important part of the study of Stoicism.
Whether physics is foundational to Stoic ethics or their relationship is reciprocal and mutually supporting is of little consequence to a Stoic practitioner. The important point for those attempting to practice Stoicism as a way of life is clear: a providential cosmos informs Stoic ethical theory and supports the psychological tools and ethical prescriptions that lead the practitioner along the path of the Stoic prokopton toward virtue and its corollary, eudaimonia.
 Brennan, T. (2007) The Stoic Life. New York: Oxford University Press, p. 35
 Long, A. (1974). Hellenistic philosophy; Stoics, Epicureans, Sceptics. Berkeley: University of California Press, p. 108
 Cooper, J. (1995) ‘Eudaimonism and the Appeal to Nature in the Morality of Happiness: Comments on Julia Annas, The Morality of Happiness.’ Philosophy and Phenomenological Research Vol. LV, No. 3, September 1995
 Annas, J. (1995) Reply to Cooper. Philosophy and Phenomenological Research Vol. LV, No. 3, September 1995
 Annas, J. (1993) The Morality of Happiness. Oxford: Oxford University Press, pp. 165-6
 Ibid, pp. 176-7
 Ibid, p. 177
 Annas, J. (2007) ‘Ethics in Stoic Philosophy’, Phronesis 52: 58-87, (p. 60)
 Ibid, p. 62
 Ibid, p. 71
 Brennan, T. (2007) The Stoic Life. New York: Oxford University Press, p. 232
 Boeri, M. (2009) ‘Does Cosmic Nature Matter?’ in Salles, R. God and Cosmos in Stoicism. Oxford: Oxford University Press, p. 173
 Gill, C. (2013). Marcus Aurelius: Meditations, Books 1-6. Oxford: Oxford University Press, p. liv
 Aurelius, M., Hard, R., & Gill, C. (2011). Meditations with selected correspondence. Oxford: Oxford University Press. p. xvi