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Topic #G57

Stoic Physics


15 February 2002
Scribe: Maya Krishnaratne


These minutes were not spoken; for another version, go to the spoken minutes



Friday’s lecture began with a discussion of Stoic physics by guest speaker, Professor Stephen Menn. He focused on the question of how Stoic physics pertains to Stoic philosophy and how this affects the rest of philosophy.  Philosophers, such as the Cynics, believed that we do not need physics in our pursuit to wisdom through philosophy.  Some Stoics also believed this.  Ariston of Chios “abolished the topics of physics and logic, saying that the one was beyond our powers and that the other was nothing to us and that only ethics mattered to us” (Lives of the Stoics, 160). However, orthodox Stoics disagree.

Menn noted that philosophy can be broken into three main groups: physics, ethics, and logic.  The Stoics described logic as what is needed to protect the rest of philosophy.  Menn used an analogy of an eggshell to the yolk inside in order to demonstrate this.  As for the physics and ethics, the difference between the two is that physics concerns nature and ethics concerns character.  While character has to do with our actions, both good and bad, nature is less about us and more about the world.  It has no immediate practical relevance and deals with things that are worth contemplating in and of themselves (i.e. the universe). It was the Stoics’ ultimate practice to look at the world as a whole because it is worth contemplating and studying.

Menn compared Aristotle to the Stoics in their views of theology.  Aristotle thought that theoretical philosophy (including physics and even mathematics) was pursued for its own sake.  And since theology included the idea of gods and other seemingly incorporeal beings and ideas, it could not be part of the physical world and so needed a discipline beyond physics.  However, to the Stoics, theology was not something separate from physics because to them, the gods are in fact bodies.  If God can control the physical universe, then he must be physical.  For as Sextus Empiricus says “according to them, the incorporeal can neither do anything nor have anything done to it” (M 8.263, IG II-28).  Things cannot act on one another without touching, either directly or indirectly.  The sun, for example, sends down rays that come in contact with things that need the sun to live.  The Epicureans also held this view.  Both the Stoics and the Epicureans believed that there existed something that could not act on or be acted upon and that is void. 

According to Aristotle, there is a distinction between practical wisdom and theoretical wisdom.  The first gives us the ability to reason.  The latter gives us the ability to contemplate those things worth contemplating.  These things are intrinsically valuable but are useless outside of themselves and do not help us to manage our lives.  The Stoics believed differently and thought that theoretical wisdom can help us practically in life and to live virtuously and happily.

A student then asked the question, “Is a thought a physical thing?”  Menn looked at the question from two different perspectives.  In terms of the mixture of things it takes to constitute a thought, such as air, the brain state, etc, a thought is a body.  In terms of the content of a thought, that which is incorporeal, it is not physical.  We can have an idea of a table and a floor and those things are corporeal, but the thought that the table is on the floor is incorporeal.  Thoughts/thinking can have causal effects without being corporeal. Bodies can act, but propositions are descriptions of things that act.  This reflects the problem that Plato came across in asserting that our thoughts act on our souls.  The Stoics try to avoid this complication.


Menn proceeded to talk about Telos formulae.  Each head of the Stoic school gives his opinion of what the goal of life is.  Cleanthes, the second head, said, “’the goal is living in agreement with nature.’”  That is, not simply living naturally, as everyone, without choice, must do, but to live deliberately conscious of it.  Chrysippus tried to refine this by saying that the goal of life is “’to live according to experience of the things which happen by nature.’”  That is, to live in accordance with science and physics. Diogenes of Babylon asserted that the goal is “’to be reasonable in the selection and rejection of natural things.’”  And Antipater said that the goal is “to live invariably selecting natural things and rejecting unnatural things.”

Physics is to help us see that things that are natural are worth pursuing and unnatural things must be avoided.  This idea depends on physics different than modern physics, which involves more of our values.  It is kind of like biology in that we talk about organs as to how they ought to act, even though they sometimes act unnaturally.  Stoic physics talks about the natural and the unnatural.  It is fundamentally biological in that they treat the cosmos like an animal. 

Menn talked about providential physics in which there exist many gods but that Zeus is the one main god.  Zeus exercises providence over the whole world.  A student commented that everything that happens seems natural.  The professor replied that, in a certain way, the Stoics see everything as natural as well.  He compared Plato’s Timaeus’ idea of matter being intrinsically chaotic with the Stoics’ view that whatever Zeus wants gets accomplished.  This is to say, that no matter what happens, things are always natural because things are the way they are because of Zeus.  But things can be contrary to nature for the individual yet still remain in accordance with the world as a whole.  For example, a disease is contrary to nature, but it doesn’t cause the entire world to be diseased.  Posidonius, the head of the Stoic school, said that the goal of life was to live to contemplate and construct the universe in accordance with Zeus.  Zeus need not worry whether an individual is sick or healthy for each individual must take care of him/herself.  Zeus gives us what he can. 

A student commented that it seems then that that which is unnatural is relative to the individual.  Menn replied that, in theory, things could be unnatural, but Zeus doesn’t allow for it.  The world is an animal, healthy in body and in soul.  In theory, it could get sick, but Zeus doesn’t let it happen.  Thus, parts can be diseased but not the whole.  So, it seems that those things that are unnatural are relative to the individual.

Menn drew a comparison between Timaeus and the Stoics again in terms of bodies.  The craftsman (God) and the soul of the world were also bodies to the Stoics.  Matter is a passive body and the soul of the world is active (fire and air).  The two things mix together and every part of the world contains both.  For Plato, there was a distinction between the craftsman and the world’s soul, but to the Stoics, the two are one and the same thing. 

The professor went on to show a comparison between Plato and the Stoics with reference to Aristocles.  The Stoics say that two things happen.  First, Zeus is a kind of fire, present in the world, consuming the world. But there are times that Zeus withdraws from the world to let there be the creation of things, like forms of matter. There are passive things that create human beings, animals, gods, etc. 


An interesting point, the professor said, was that “the primary fire is like a kind of seed, containing the rational principles and cause of all things and events, past, present, and future…all things in the cosmos are organized extremely well” (Aristocles in Eusebius Prep Ev 15.14, IG II-61).  For the Stoics, the ordered world hasn’t always existed.  For example, there haven’t always been horses for how could there have been a first horse if there have always been horses?  It seems that things must have been formed from a seed and not from sexual reproduction.  Zeus leaves a fiery body behind (with the same power of a seed) to produce things.  And the Stoics don’t believe only that there are seed-like principles, but they also believe that Zeus is a seed-like being, a seed of the world. 

“In the beginning, then, he was by himself and turned all substance into water via air; and just as the seed is contained in the seminal fluid, so this, being the spermatic principle of the cosmos, remains like this in the fluid and makes the matter easy for itself to work with in the generation of subsequent things” (DL 7.136, IG II-20).

Thus, the world that Zeus makes is very much like what happens to a seed and all the processes it goes through in growing.  Zeus makes it so that the world develops in a certain designed way. 

The professor then paused a moment to acknowledge that this idea of the creation of the world seems bizarre.  The kind of physics we need is that which is in accordance with the cosmic plan if it is to lead us to virtue.  Timaeus doesn’t speak in this way, but Stoics think that Plato can’t explain how an incorporeal god can act on the physical world.  The metaphors that the Stoics use could be real if we knew enough about the physical world.  We don’t know the kind of processes involved in an incorporeal god acting on the corporeal world.  The Stoics try their best to see what the real story would have to be like and so they apply physics to their conception of Zeus’ creation of the world.  Zeus’ knowledge of nature is the reason he acts in accordance with nature and nature thus tells him what to do.  We can know general principles, which is less than what Zeus knows, so we can act in accordance with nature, insofar as it is in our power to do so. 

A hymn by Cleanthes partly quoted by Epictetus helps us to see that even an evil person must unwillingly follow Zeus’ plan:

“Lead me, O Zeus, and you L Fate, to whatever place you have assigned me; I shall follow without reluctance, and if I am not willing to, because I have become a bad man, nevertheless I will follow.” (SVF 1.527, IG II-22)

However, a good person will follow the plan because he understands and values Zeus’ plan and is willing to do so. 

A question was raised as to why Aristotle didn’t consider physics a practical science. Menn replied that it is in a very general way.  We act so as to maximize the contemplation of God, not because God gives us orders, but because God is what is desirable.  For the Stoics, knowledge of the world isn’t only desirable, but it also does contain practical advice – it shows us what our roles are and how to act as a functioning part of the world.

Another question was asked about human beings and if it was only humans who can live not in accordance with nature.  Furthermore, does it require rationality to not act in accordance with it?  Menn replied that it is true that it requires rationality and thus only human beings can act without accordance to it.  There is no evil in the world apart from human evil. He also said that it seems to follow that there are very few, good rational beings that are human, for most of them are gods.

The Stoics’ view of Zeus recognizes his two main roles.  The first is when the world is only the vast fire of Zeus.  In the second instance, when he withdraws from the world, he is still there, just not fully immersed in it.  The only time that he can be apart from the world is when there is no world, because he is in fact, the world.  Menn reminded us that, since the Stoics believe that Zeus is constantly keeping the world a good place, nothing bad could ever take over (i.e. disease can’t overtake the entire world at one time).