C H R Y S IP P U S ’ TH EO R Y O F PN EU M A
Paul Hager
I.
MODE OF ATTACKING THE PROBLEM
The early Stoics divided philosophy into three different but intimately
related parts: logic, physics and ethics.1 The cornerstone of their physics
was a continuum theory of the cosmos—the first systematic continuum
theory in Greek philosophy.2 According to the Stoics the universe is a
single, corporeal, infinitely divisible whole. All changes or processes,
whether local or cosmic, are viewed as alterations in the disposition of this
single, dynamic, eternal substance. In the manner of the Greek meta­
physical tradition, the Stoics sought to provide a rational account of the
universe in terms of permanent realities that underlie apparent
impermanence.
Chrysippus is standardly depicted as producing the definitive formulation
of the metaphysical views of Zeno and Cleanthes, his illustrious Stoic
predecessors. A reconstruction of his theory of pneuma is timely because it
turns out to support recent questioning of the tradition that sees Chrysippus
as little more than a clever systematiser of other people’s ideas.5 Instead, he
is more accurately described as a bold and original thinker who provided
Stoicism with much needed rigour. More than historical accuracy is
involved here since, as recent holistic trends in physics testify, systematic
continuum theories are interesting in their own right.
Unfortunately, attempts to clarify such key elements of Stoicism as the
doctrine of pneuma are hindered by the paucity of reliable source material.
As is well known, no complete work by any philosopher of the early or mid­
dle Stoa survives. Our evidence consists of quotations—some attributed to
individual Stoics, others simply to ‘the Stoics’—second-hand reports and
material from other authors which, with varying degrees of confidence, is
thought to have been derived from the Stoics. In addition, the later Stoics
had little interest in physics. Thus it is hardly surprising that the evidence as
a whole is confusing and contradictory to the point of bewilderment.
1. Diogenes L aertiu s, Lives o f Eminent Philosophers, vii 39-40, tra n s. R. D. H icks, 2 vols,
H einem ann (1925). F o r discussion see A . A. L ong, Hellenistic Philosophy, D uckw orth (1974),
pp. 118-121.
2. S. S am b u rsk y has stressed th e originality o f th e Stoic co n tin u u m th e o ry in his Physical
World o f the Greeks, R ou tled ge an d K egan P au l (1956), C h . VI a n d Physics o f the Stoics,
R outledge an d K egan P au l (1959).
3. A useful su m m ary o f this tren d is provided by J. G o u ld , The Philosophy o f Chrysippus, E.
J. Brill (1970), C h s II an d VII.
98
PA UL HA GER
Faced with this ‘inconsistent jumble of fragments’,4 it might be con­
cluded that the task of unravelling Chrysippus’ doctrine of pneuma is a
hopeless one. However, such a conclusion errs in giving equal credence to
all fragments. Likewise, since it is certain (from many of the more reliable
sources) that the doctrine of pneuma underwent some modification as it
passed successively through the hands of Zeno, Cleanthes and Chrysippus,
it hardly needs emphasising that inconsistencies will only be multiplied if we
insist on saddling each of these individuals with all of the views attributed to
‘the Stoics’. Yet, this has been the major tendency in the literature on the
subject. It is understandable, given the fragmentary state of the evidence,
that the emphasis should be on what is held in common by the early Stoics.
However, pressed too far, this approach to the sources becomes counter­
productive.
Considerations such as these suggest the following mode of attack on the
problem of clarifying Chrysippus’ theory of pneuma·.
1. Identify a minimal set of basic ideas which comprise the foundations of
Stoic physics. Such basic ideas (hereafter referred to as ‘minimal Stoic
physics') should be non-controversially attributable to each of Zeno,
Cleanthes and Chrysippus.
2. Identify the main areas of disagreement and controversy that arise once
this minimal set of propositions is extended.
3. Identify the sources which most reliably attribute views about pneuma
to Chrysippus, e.g. a fragment that purports to be a direct quotation
from Chrysippus’ writings is more reliable than one that simply attrib­
utes a view to Chrysippus.5 This distinction is important because in
later centuries Chrysippus was seen as a spokesman for Stoicism.
Authors hostile to Stoicism are therefore likely to have burdened him
with the sins of others.
4. Combine the results of (1) and (3) and, hopefully, deduce from this the
position taken by Chrysippus in the disagreements and controversies
listed in (2).
5. Use any insights gained about Chrysippus’ position to bring out
similarities and differences with respect to Zeno and Cleanthes.
Such a strategy might seem so obvious as to be hardly worth enumerating,
were it not for the fact that when carried through it leads to some novel
results. In particular, it supports the view that Chrysippus was a major
innovator in Stoic physics.
4. M. L apidge, ‘A rch ai an d S toicheia: A P ro b lem in S toic C o sm o lo g y ’, Phronesis. 18 (1973),
p. 240.
5. T his p ro ced u re is a d o p te d by J. G ould in his Philosophy o f Chrysippus.
CH R Y SIPPU S’ THEORY OF PNEUM A
II.
99
MINIMAL STOIC PHYSICS
From the many sources what basic physical theories can reasonably be
held to be definitely common to Zeno, Cleanthes and Chrysippus? It is evi­
dent that the three key explanatory concepts in Stoic physics are:
(a) Principles (archai)
(b) Elements (stoicheia)
(c) Pneuma
The non-controversial points about each of these are as follows:
(a) Principles
The single cosmic substance is characterised by two principles (archai),
one active (to poiouri), the other passive or acted upon (to paschori). These
principles serve both a cosmogonical and a cosmological function, i.e. they
explain the genesis of the cosmos as well as providing, in very general terms,
an account of the present state of the cosmos.6
It is a symptom of the unity of Stoic philosophy that the active principle is
variously (and apparently interchangeably) described as god (theos), nature
(physis) and creative fire (pyr technikori). The passive principle is described
as unqualified matter (apoios hyle). The active principle acts on the passive
principle to produce qualified or propertied matter.
(b) Elements
With minor modifications7 Stoic physics takes over the traditional
quartet of elements favoured by many Greek philosophers. There is general
agreement:
(i) that the elements are formed in the cosmogonical process via the
active principle’s action on the passive one (fire is a possible exception
to be discussed shortly).
(ii) that elements in various combinations constitute material objects.
(c) Pneuma
The early Stoics were agreed that pneuma (literally ‘breath’ or ‘air’)
permeated the bodies of living organisms constituting a corporeal soul
6. D etailed arg u m en t in su p p o rt o f th e dual function o f the archai is given in R. B. T o d d ,
‘M onism an d Im m anence: T he F o u n d a tio n s o f Stoic P hysics’ in J. M . Rist (ed.), The Stoics,
U niversity o f C a lifo rn ia P ress (1978).
7. S. S am b u rsk y , The Physical World o f the Greeks, o p .c it., p. 133, characterises the differrences as follow s:
A ccording to A risto tle ’s d efin itio n , the q u ality com m on to the active elem ents is h eat, fire
being hot an d d ry , while air is hot an d m oist. T he S toics defined th e elem ents differently,
a ttrib u tin g only o n e q u ality to each, thus m aking fire hot an d air cold, earth dry an d w ater
m oist. But th e S toics agreed with A ristotle in a ttrib u tin g active qualities to fire an d air.
100
PA U L HA GER
(psyche). They held that the soul’s command centre (hegemonikori) was in
touch with all parts of the body via movements of pneuma. They used this
scheme to explain sensation, speech, bodily movement, etc. In addition, the
early Stoics often talked about the universe as if it were a single large
biological organism so that the idea of a universal soul arose, though there
was no agreement about its location. As we shall see, a systematic, coherent
account of these matters awaited the work of Chrysippus.
III.
MAJOR DISAGREEMENTS AND CONTROVERSIES
IN STOIC PHYSICS
Beyond the common ground just established for principles, elements and
pneuma, disputes are legion. The doctrine of principles has proved
especially difficult to elucidate satisfactorily.8 The reason for this is simple.
Stoic monism demands a single primal substance, yet, influenced by their
philosophical predecessors, the Stoics were convinced that genesis or change
involved interaction of opposite forces. They also held that only corporeal
things are capable of acting or being acted upon, hence their single, primal
substance was in danger of becoming two substances, so threatening their
monism. The various sources oscillate between at least three positions:
(a) The principles are not corporeal because they are abstractions from a
single substance.
This protects monism, but leaves the problem of explaining how abstract
non-corporeal principles interact with one another.
The principles are corporeal because to poioun and to paschon are
different descriptions referring to the same substance.
This protects monism, but the problem of how a single body can interact
with itself is posed.
(b)
The principles are corporeal because they are different substances that
mix homogeneously to form the primal substance.
This position satisfies the requirements for interaction of opposites,
seemingly at the price of abandoning monism.
(c)
These difficulties are compounded by the metaphorical titles given to the
supposedly inseparable principles, e.g. ‘creative fire’, ‘god’, etc. This fact
underlies the central dispute about elements: is creative fire the same as the
8. D etailed discussions are co n tain ed in M . L apidge, ‘A rchai an d S toicheia: A P roblem in
Stoic C o sm o lo g y ” , o p .c it; M . L apidge, ‘Stoic C o sm o lo g y ’ in J. M. Rist (ed.). The Stoics, pp.
161-185; R . B. T o d d , ‘M onism an d Im m anence: T he F o u n d atio n s o f Stoic P hysics’, o p .cit.
CH R Y SIPPU S’ THEORY OF PNEUM A
101
element fire? Some ancient sources suggest that the two can be identified.9
But then what about the inseparability of the two principles? Pneuma is
widely described as a mixture of air and fire so that these uncertainties are
compounded when some sources suggest air is mixed with creative fire. In
addition, the Stoics agreed that the universe is cyclic, periodically under­
going conflagration, (ekpyrosis), so as to return to the original
primogenitive substance. (This original substance is metaphorically
described as ‘fire’ in these contexts—probably a reference to ‘creative fire’.)
There are also other disputes about pneuma which will be considered
where appropriate in the remainder of this paper. At this point it can be
noted that any satisfactory reconstruction of Chrysippus’ physics should
provide clearcut answers to these disputes about the principles and
elements, if only because a philosopher who ‘attained exceptional eminence
. . . and showed the greatest acuteness in every branch of the subject’10
would be hardly likely to tolerate such patent inconsistencies in his work.
IV.
CHRYSIPPUS ON PNEUMA
Notwithstanding the disagreements just outlined, there is widespread
concurrence in the recent literature on Stoicism that Zeno, Cleanthes and
Chrysippus follow a similar pattern in the use they make of principles,
elements and pneuma in their physics. Both in cosmogony and cosmology,
so this orthodox view maintains, principles underlie elements and elements
underlie pneuma (since, as widely reported in the sources, pneuma is a
mixture of air and fire).11
Where it is conceded that Chrysippus made an original contribution, the
most common view is that he developed a theory of cosmic pneum a.'2 For
Zeno and Cleanthes pneuma in the sublunar world is restricted to living
organisms whereas Chrysippus suggests that pneuma pervades the entire
universe. Since pneuma is taken to be a mixture of elements the orthodox
view is apparently compatible with this move.
However, it has not been generally noticed that Chrysippus’ innovation
has implications that place him in direct conflict with the orthodox view.
This follows from developing the full import of the following quotations
from Chrysippus’ book On Physical States, which fortunately were
preserved for us by Plutarch, an arch opponent of Stoicism:
9. T hese ap p e a r to be co n fu sed secondary sources. E vidence th at th e early Stoics kept th e tw o
kinds o f fire d istinct is provided by M . L apidge, ‘A rchai an d S toicheia: A P ro b lem in Stoic
C osm o lo g y ’, p. 267 ff, and also in his ‘Stoic C osm o lo g y ’, p. 167.
10. D iogenes L aertiu s, o p .c it., vii 179.
11. M a jo r exceptions are th e papers by M . L apidge an d th e one by R. B. T odd n oted above.
Both a u th o rs show an aw areness o f the difficulties in the o rth o d o x view.
12. F o r detailed discussion o f this see the tw o pap ers by M. L apidge n o ted previously.
102
PA U L HAGER
The physical states are nothing else but spirits, because the bodies are
made cohesive by them. And the binding air is the cause of those bound
into such a state being imbued with a certain property which is called
hardness in iron, solidity in stone, brightness in silver.
Matter, being inert by itself and sluggish, is the substratum of the proper­
ties, which are pneumata and air-like tensions giving definite form to
those parts of matter in which they reside.13
The binding state of the pneuma of a body was called the 'hexis' or ‘bind­
ing spirits’ by Chrysippus, who thought of pneuma as very tenuous or ‘air­
like’. From this and the above quotations it is clear that pneuma is respon­
sible for the properties of both organic and inorganic objects. Looking at it
from another angle, the single substance of the universe is thoroughly per­
vaded by a continuum of pneuma, the properties at any place being deter­
mined by the structure or disposition of the pneuma at that place.
Chrysippus envisaged a hierarchy of pneuma dispositions.14 The overall
pneuma of an object could be seen as a physical field resulting from sum­
ming the pneuma responsible for the various components of the object.
Thus stones and other inanimate objects have the single pneuma disposition
hexis. A human being, for example, would also have a hexis underlying the
skeletal structure. Besides hexis, plants have a further pneuma disposition,
physis. Humans also have a physis governing such things as hair and finger­
nails. Next in the hierarchy is psyche, a further pneuma disposition found in
all animals, governing their capacity for having mental images and desires.
Finally, humans and gods have logos, the pneuma for thought, pneuma in
its greatest tension. (This hierarchy is similar to Aristotle’s one for souls
where each level also incorporates all of those below it.)
Chrysippus’ innovation, then, amounts to a generalisation of the con­
tinuum theory of his predecessors into a field theory in which pneuma is the
physical field that generates all properties of material objects. Though some
writers acknowledge this they nevertheless persist in attributing to Chrysip­
pus the orthodox view (that pneuma is a mixture of air and fire), apparently
without realizing that blatant inconsistency thereby results.1* This is easily
demonstrated: pneuma is the generator of properties and elements have
properties, so elements are pervaded by pneuma; therefore pneuma is
13. P lu ta rc h , De Stoic. Repugn. 1053f. B oth passages are q u o ted in S. S am bursky, Physics
o f the Stoics, p p . 7-8.
14. A discussion o f this p o in t, including relevant sources, is to be fo u n d in M . L apidge, ‘Stoic
C o sm o lo g y ’, o p .c it., p. 171 ff.
15. S. S am b u rsk y , Physics o f the Stoics, o p .c it., clearly establishes th at pneuma is a m ixture
o f air and fire (pp. 2-4) an d th en goes on to identify pneuma as th e ‘carrier o f all specific
p ro p e rtie s’ (p .7 ff). J. G o u ld , The Philosophy o f Chrysippus, pp. 100-101, su p p o rts the sam e
view. O th er exam ples are easily found.
CH R Y SIPPU S’ THEORY OF PNEUM A
103
logically prior to elements and so is not a mixture of them .16 To make the
point another way, elements cannot be mixed to produce pneuma because
something that is an element is already pervaded by pneuma. The element
air has the property of being cold because of the pneuma that pervades it.
So to mix two elements is to mix two things that are already pervaded by
pneuma. This is no more a way to produce pure pneuma than mixing gold
with silver is a way to produce pure electrons.
Before grafting Chrysippus’ innovation onto our minimal Stoic physics
and from there attempting a reconstruction of his physics, a possible objec­
tion to the above argument needs to be considered. Whilst agreeing that
Chrysippus holds pneuma responsible for all properties of the current state
of the universe, someone might argue that pneuma is still a mixture of air
and fire from an earlier stage. This position would preserve Chrysippus as
an adherent of the orthodox view since he would agree with Zeno and
Cleanthes that pneuma comes after principles and elements in cosmogony.
However, there are compelling reasons for rejecting this interpretation. The
quotations preserved by Plutarch made it clear that Chrysippus ascribed all
properties of material things to pneuma dispositions. So the price of keep­
ing Chrysippus ‘orthodox’ would be a commitment to the rather odd view
that present elements are different from their counterparts in earlier stages
of the universe.
More generally, such a view destroys symmetry between cosmogony and
cosmology, whereas there are ancient sources that suggest Chrysippus
retained such symmetry by identifying pneuma with the active principle.17
The implications of this will be detailed shortly, but for the present we can
note that it leads to a simple, elegant theory as opposed to the complexities
that characterise the rival view. A sample of these complexities is provided
by R. B. Todd18 whose involved but ingenious account requires pneuma to
have the substance of aither (i.e. Aristotle’s fifth element), but the proper­
ties of the active principle. On this account pneuma continues the work of
the active principle in the later stages of the cosmos. Todd admits that no
ancient sources explicitly support his account, yet rather implausibly
dismisses as ‘vague doxographical reports’ those sources that identify
16. It could be o b jected th a t this arg u m en t ignores th e possibility th a t w hen air is m ixed w ith
fire th eir ch aracteristic p ro p erties, (cold an d hot respectively), cancel o n e a n o th e r o ut leaving
pneuma. But d o n ’t they have o th er pro p erties, e.g. fire has co lo u r, brightness, etc.? A nyw ay,
if such can cellatio n is possible earth an d w ater should also fo rm pneuma o r its equivalent when
m ixed.
17. T he tw o p ap ers by M. L apidge n oted previously co n tain discussion an d references to
sources on this p o in t.
18. R. B. T o d d , ‘M onism an d Im m anence: T h e F o u n d a tio n o f S toic P h y sics’, o p .c it., p.
149ff. N ote th at T o d d ’s view denies th at pneuma is an a ir /fir e m ixture.
104
PA U L HAGER
pneuma with the active principle. Chrysippus has been often described as
‘the greatest logician of ancient times’. '9 That only increases the probability
that he did indeed develop the economical physics that results from
generalising the pneuma field theory across cosmogony and cosmology.
V.
A LIKELY RECONSTRUCTION OF CHRYSIPPUS’
BASIC PHYSICS
In Section II the active principle (‘god’, ‘nature’, ‘creative fire’) was iden­
tified as the origin of the properties of matter. Section IV found Chrysippus
assigning this role to pneuma. Since some ancient sources have him identify­
ing the active principle with pneuma, this is obviously the starting point for
grafting his field theory of pneuma onto our ‘minimal Stoic physics’
previously enumerated. What are the implications of this?
For a start, it is clear that Chrysippus is committed to a corporeal pneuma
i.e. a corporeal active principle. This is so because all of the Stoics agreed
that souls (pneuma dispositions) are corporeal. In positing a cosmic pneuma
(or soul) to explain all properties of matter, Chrysippus rejected the
‘pneuma equals air plus fire mixture’ view of his predecessors, but retained
a corporeal pneuma and mixed it with corporeal hyle to account for all
stages of the cosmos. This is supported by the following testimony of
Alexander of Aphrodisias:
Chrysippus’ theory of mixture is as follows: he supposes that the whole
of nature is united by the pneuma which permeates it and by which the
world is kept together and made coherent and interconnected.20
This commitment to corporeal principles lands Chrysippus in the difficul­
ty noted in Section III, viz. it appears to be inconsistent with monism. After
all, there is a venerable maxim that suggests two distinct bodies can’t be in
the same place at the same time. However, I will now argue that the real
significance of Chrysippus’ much maligned theory of mixture is that it
enables his two corporeal principles to be reconciled with Stoic monism.21
As is well known, Chrysippus proposed a type of mixing that involved the
complete interpenetration of two bodies such that both bodies retain their
own properties yet every particle of the mixture is homogeneous. Empirical
19. B. M ates, Stoic Logic, Berkeley a n d Los A ngeles, (1961), p .7.
20. A lex an d er o f A p h ro d isias, de mixtione, 216, 14, q u o ted in S. S am bursky, The Physical
World o f the Greeks, p. 134. T h is q u o ta tio n from A lexander also alludes to th e fam o u s tension
o f pneuma.
21. R . B. T o d d , Alexander o f Aphrodisias on Stoic Physics, L eiden, E. J. Brill, (1976), P art
T w o, p resen ts a suggestive discussion o f C h ry sip p u s’ theory o f m ixture arriving at sim ilar c o n ­
clusions to th o se achieved here.
CH R Y SIPPU S’ THEORY O F PNEUM A
105
examples were used to illustrate the point, e.g. in contradiction of
Aristotle’s view that a drop of wine in the sea would lose its wine-like pro­
perties and become part of the water, Chrysippus held that the wine and the
sea would form a homogeneous mixture by completely interpenetrating one
another. However, such examples should not mislead us from the main in­
tent of the theory. For Chrysippus pneuma is a body that thoroughly in­
terpenetrates another body, hyle, so as to produce the objects we ex­
perience, i.e. his metaphysics commits him to the view that all objects
violate the venerable maxim that two distinct bodies can’t be in the same
place at the same time. If critics of Chrysippus wanted to start experiments
with mixing to prove their argument, they would be missing the point. What
they need is a superior metaphysics.
It is not surprising that Chrysippus was nevertheless interested in mixing
experiments. No sensitive tests that could disprove his ‘wine in the sea’
theory were available and to that extent his pneuma theory was supported.
However, the fact that modern technology enables us to prove that wine
doesn’t interpenetrate the sea, in no way disproves the metaphysical
pneuma interpenetration theory. Rather we reject the latter because our
current best theories rule out corporeal interpenetration.
Thus, according to Chrysippus, Stoic monism is preserved because in the
pre-cosmic chaos pneuma interpenetrates hyle uniformly so that no volume
of the mixture, however small, lacks homogeneity. There truly can be said
to be a single primal substance. Though modern science rules out such cor­
poreal interpenetration, non-corporeal forces can interpenetrate corporeal
media. To this extent Chrysippus’ corporeal field theory of pneuma
anticipates later field theories.
How does Chrysippus’ physics as reconstructed thus far relate to the
second of the explanatory concepts in Stoic physics, viz. elements? From
one point of view there is radical change from the position of Zeno and
Cleanthes. However, there is also a sense in which little is changed. The
radical change is that elements are no longer required in fundamental
physical explanations, having been displaced by pneuma. Thus formation
of elements is no longer a vital stage in cosmogony, since it represents
nothing more than some cosmic pneuma arrangements rather than others.
Likewise material objects are more informatively characterised by pneuma
dispositions (hexis, physis, psyche, logos) than by their elemental composi­
tion. In modern parlance, element theory has been reduced by pneuma
theory.
However, as noted, there is also a sense in which little has changed. Just
as the reduction of electron-proton-neutron theory to lepton-hadron theory
doesn’t do away with electrons, protons and neutrons or their characteristic
106
PA U L H A GER
phenomena; neither does pneuma theory do away with the elements.22
Paradoxically, one of the advantages that pneuma theory has over its earlier
rival opens up a new career for the elements. In principle, changes in
pneuma/hyle concentration could be quantified. However, it is clear that
Chrysippus would have been restricted to rough rules of thumb such as:
Presence of fire/air
J
High pneuma concentration
implies
Absence of water/earth )
Low hyle concentration
)
i Low pneuma concentration
> implies <
Presence of water/earth *
■»
( High hyle concentration
This perhaps explains why Chrysippus in the earlier quotations preserved
by Plutarch refers to pneuma as ‘air-like tensions’. The suggestion that
variations in pneuma concentration are indicated by the elements is perhaps
supported by the following quotation from Galen:
According to (the Stoics) the soul is a pneuma, as is also organic nature.
Only the pneuma is moister and colder in nature, and drier and warmer
in the soul. Thus it is a kind of primordial matter very similar to the soul,
and the form of the primordial matter comes about through the mixture
of the airy and fiery substances in suitable proportions.23
Hence there were good reasons why Chrysippus might have continued to
refer to air/fire mixtures even though this was no longer an explanation of
the nature of pneuma. This would understandably have the effect of
obscuring Chrysippus’ innovations whilst emphasising continuity with Zeno
and Cleanthes.
There are a number of other points to be made about this suggested
reconstruction of Chrysippus’ physics. First, it successfully solves the prob­
lems raised in Section III. As has already been shown, an account of the
principles is offered which deals adequately both with the generation-fromopposites problems and the threat to Stoic monism. The ambiguity about
creative and destructive fire doesn’t arise because the two belong in dif­
ferent categories, the former being pneuma, the latter being matter in a
certain pneuma disposition. Second, the cosmic pneuma provides the basis
for an explanation of the stability and coherence of the cosmos via the
theory of tensional motion. The cosmos is unified by the all-pervading
Absence of fire/air
22. M . L apidge, ‘A rch ai an d Stoicheia: A P roblem in Stoic C o sm o lo g y ’, o p .c it., p. 271 ff,
argues th a t C h ry sip p u s ab an d o n e d the d istin ctio n betw een principles (archai) an d elem ents
(stoicheia). P e rh a p s this provides indirect su p p o rt for th e present claim th at only archai are
essential fo r fu n d am en tal physical explanations.
23. G alen , de anim. mor., IV 783, q u o ted in S. S am bursky, The Physical World o f the Greeks.
p. 134.
CH R Y SIPPU S’ THEORY O F PNEUM A
107
pneuma whose tension provides contact between all of the parts and holds
them together. Speech, hearing, locomotion and other bodily functions are
explained in terms of pneuma tension.24 By adding the idea of tension to his
pneuma field theory Chrysippus was able to explain a wide range of
phenomena more satisfactorily than had his Stoic predecessors. Third, if
this account of Chrysippus is correct, it helps explain the significance of the
dissolution of the universe into fire (ekpyrosis), signalling the end of one cy­
cle and the start of another. The cycle starts with pneuma uniformly inter­
penetrating hyle, the interpenetration becomes non-uniform as the cycle
proceeds and returns to uniformity at ekpyrosis. In thermodynamic terms,
in the pre-cosmic chaos the entropy is at a maximum (tension of the pneuma
at a minimum). As the cosmos is formed entropy decreases (as tension of
the pneuma is increased). Finally, ekpyrosis is inevitable, signalling a return
to maximum entropy (and minimum tension). Perhaps the fact that each
cycle starts with the same uniform single substance partly explains why the
Stoics thought that each successive universe is identical. Notwithstanding
these tentative suggestions, ekpyrosis remains a problematic area of Stoic
cosmology. Logos, as well as pneuma, and the relationships between their
various aspects, would need to figure in any satisfactory account of the
matter.
VI.
CONCLUSIONS
It will be useful to test the ideas developed in this paper against a
‘dilemma for the Stoics’ posed by Alexander of Aphrodisias.25 He begins
by setting out three Stoic theses:
(1) The Stoics posit two archai, hyle (passive) and theos (active);
(2) The Stoics say that theos is corporeal insofar as it is eternal and
intelligent pneuma going about the business of creation;
(3) The Stoics hold that pneuma is composed of some of the four created
elements.
Alexander’s dilemma is that either pneuma is a compound of created
elements, which clashes with (1) and (2), or pneuma is some sort of ‘fifth
body’, which clashes with (3).
The orthodox view is in trouble with Alexander’s dilemma because by
making Chrysippus’ theory continuous with that of his predecessors, it is
committed to all three theses. Our alternative theory has no difficulty from
Alexander because it doesn’t commit Chrysippus to all of the Stoic theses
24. See, e.g. J. G o u ld , The Philosophy o f Chrysippus, C h . V, P a rt 3.
25. T he d ilem m a is p resented an d discussed in M . L apidge, ‘A rchai an d Stoicheia: A P roblem
in Stoic C o sm o lo g y ’, o p .c it., p. 276ff. It is also discussed in R. B. T o d d , Alexander o f
Aphrodisias on Stoic Physics, P a rts tw o an d three.
108
PA UL HA GER
found in the literature. Thus it is suggested that Zeno and Cleanthes assent
to (1) and (3), which are consistent, and reject (2). Chrysippus takes the dif­
ferent stance of accepting (1) and (2) and rejecting (3), thus emphasising his
departure from the tradition that preceded him.
It has been argued that Chrysippus’ contribution to Stoic natural
philosophy departed from the views of his predecessors in vital and funda­
mental respects, so much so that it is misleading to emphasise continuity as
the main feature. While it is generally agreed that Chrysippus originated the
cosmic pneuma, this paper has proposed that this move was based on two
more fundamental innovations. First, an insistence on each of the two prin­
ciples being corporeal, together with the theory of mixture needed to render
this claim plausible. Second, the rejection of the idea that pneuma is a mix­
ture of air and fire, together with a down-grading of role of elements in
physical explanation. Whilst some scholars endorse one or other of these in­
novations, it is urged that both are essential in order to make Chrysippus’
physics internally consistent.