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.
I
Bodies
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.)
II
Breath
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.