First posted on the Stoicism Today blog. Now published in Stoicism Today: Selected Writings II (2016).
In my workshop at Stoicon 2015 I talked about Stoic physics and about its relationship with what we would today call religion and science. My aim was simply to try to give participants a sense of the broader ‘Stoic worldview’ beyond their practical advice about how to live well.
The Stoics begin with the claim that only bodies exist (Cicero, Acad. 1.39). Everything that exists is a physical thing. Anything that has any kind of causal power must ultimately be a physical body. So, if the Stoics claim that virtue impels us to act, for instance, and so has some causal power, then virtue must be a body. And they think it is: virtue is an excellent mental state, i.e. the physical soul organized in an optimal way. Closely connected to this claim that only bodies exist, the Stoics reject the existence of universals (i.e. Plato’s Ideas or Forms). Only particulars exist. So when they talk of ‘virtue’ they are not talking about some general concept or abstract ideal, which doesn’t exist, but rather about specific virtuous actions or specific optimal brain states. (Talk of brain states might sound anachronistic but it is pretty much what they have in mind.)
They go on to claim that all bodies are composed of two principles or aspects: matter and ‘breath’ (pneuma) (Diog. Laert. 7.134). Matter is passive; breath is active. Breath is what makes things alive, and because everything is composed of both matter and breath, everything is alive. Breath comes in a variety of degrees of ‘tension’ (tonos) and the greater the tension the more complex the object. Inanimate objects such as stones have the lowest level of tension; living things such as plants have a higher degree; animals with the powers of sensation and movement are higher again; adult humans with rationality have the highest degree of tension. The higher the tension of the breath, the more complex the living organism will be (see Philo, in Long-Sedley 1987, 47P-Q). An important point here is that there is no difference in kind between a stone and a human being, only a difference in tension of breath (we might say a difference in internal organization or structural complexity; A.A. Long once proposed ‘wave-length’ as a way of thinking about this).
III Nature and God
The physical world, Nature as a whole, is a continuum and is infinitely divisible; the divisions between physical objects are to an extent only relative. Ultimately there is just one physical thing, Nature, of which we are all parts. The breath that structures and animates all of Nature the Stoics call ‘God’. Some sources say God is the breath, the soul of the world, just as the breath in our bodies is our soul. Other sources identify God with Nature as a whole, with the breath being his soul and the matter his body (the difference is between God being an animating force within Nature or simply being Nature). So, Nature is a living organism comprised of a soul and a body, breath and matter, and because, by definition, there is nothing greater than this, it, if anything is, must be God. On either view, we are fragments of God. If God is the world soul, the breath animating all of Nature, then the breath that animates us, our soul, is simply one part of that.
IV How Religious?
It is difficult to know how serious this talk of ‘God’ was. The early Stoic Cleanthes appears very sincere in his ‘Hymn to Zeus’, for instance, and we have no reasons to doubt his sincerity. However the Stoics were also well known for offering allegorical interpretations of the pagan Gods, including allegorical interpretations of the portraits of the Gods in Homer for instance. Famously, the Stoic Chrysippus once said that Zeus and his wife Hera are actually the active and passive principles in Nature, breath and matter. (In one source, Diog. Laert. 7.147, divine names for Nature are explained on the basis of their etymology.) Much later, in the third century AD, the philosopher Plotinus said that the Stoics bring in God into their philosophy only for the sake of appearances (Enn. 6.1.27). If ‘God’ is simply another name for Nature then it doesn’t really do much work in their philosophy; it doesn’t add or explain anything, so one might easily drop the word without any obvious loss. However the idea of a divine breath permeating Nature would later influence the Christian idea of a Holy Spirit (pneuma), and then would be interpreted by Church Fathers and others looking to harmonize Stoicism with Christianity right through to the seventeenth century. Perhaps that afterlife gives Stoic accounts of pneuma stronger religious overtones than they originally had. It is very hard to know. But again, Cleanthes’ Hymn appears quite sincere.
V How Scientific?
When the Stoics developed this idea of the soul as breath permeating the body they were doing so in dialogue the science of their day. In the image they give of the human soul comprised of a commanding centre with tentacles spreading pneuma (breath) throughout the body was inspired in part by the work of early anatomists (esp. Praxagoras; also Erasistratus) who were cutting open bodies and finding arteries and nerves. Chrysippus located the commanding centre of the soul in the chest (following Praxagoras), which of course contains the heart and arteries leading off it that spread through the entire body. (Praxagoras thought that arteries were pipes also connected to the lungs, carrying pneuma.) A later Stoic disagreed with Chrysippus and said the commanding centre of the soul was in the head, which of course contains the brain with nerves leading off it spreading through the entire body. This shift in position may well have been prompted by further observations (i.e. dissections): the distinction between arteries and nerves was still unclear in Chrysippus’ day and he commented that the scientific evidence was only tentative and one ought to wait for further discoveries. The important point to make here is that all this talk of a soul pervading and animating the body was actually part of a first step towards developing an account of the brain and nervous system. As crude as it may have been, this was a theory based on the cutting-edge scientific knowledge of the day.
VI Some Concluding Comments
The Stoics give us arguments for why we ought to think that Nature is rational, alive, and intelligent. We have those properties, nothing without those properties can give birth to something with them; therefore they must be properties of Nature (Cicero, Nat. D 2.22). (There are philosophers of mind today who continue to argue against the claim that consciousness could be an emergent property.) The Stoics then call this living Nature ‘God’. If Nature (or the Cosmos) encompasses everything, and if only bodies exist, and if God is something than which there is nothing greater, then it looks as if God must be identified with Nature. God cannot be anything lesser than Nature and cannot be anything outside Nature. However it remains difficult to know how seriously we ought to take this: is it a devout pantheism (you really ought to worship Nature), simply a deflationary use of language (when you say ‘God’ what you really mean is Nature), or a cautious pragmatism (rather than deny the existence of God, let’s call Nature ‘God’)? We do know the Stoics repeatedly engaged with (what we would now call) the science of their day: Chrysippus drew on the anatomist Praxagoras, the Stoic Posidonius studied botany and geology, a later Stoic, Cleomedes, wrote on astronomy, and Seneca wrote not just his ethical works but also his Natural Questions (on meteorology). The Stoics wanted to understand Nature because Nature taken as a whole is the greatest thing there is and we are parts of it. They aspired to a ‘smooth flow of life’, which they defined as a life in harmony with Nature, something that will require at least some appreciation of how Nature works. Whether we choose also to call Nature ‘God’ or ‘Zeus’ or ‘Gaia’ is perhaps less important.