Stoic Philosophy of Mind

Stoicism was one of the most important and enduring philosophies to
emerge from the Greek and Roman world. The Stoics are well known for
their contributions to moral philosophy, and more recently they have
also been recognized for their work in logic, grammar, philosophy of
language, and epistemology. This article examines the Stoics'
contributions to philosophy of mind. The Stoics constructed one of the
most advanced and philosophically interesting theories of mind in the
classical world. As in contemporary cognitive science, the Stoics
rejected the idea that the mind is an incorporeal entity. Instead they
argued that the mind (or soul) must be something corporeal and
something that obeys the laws of physics. Moreover, they held that all
mental states and acts were states of the corporeal soul. The soul (a
concept broader than the modern concept of mind) was believed to be a
hot, fiery breath [pneuma] that infused the physical body. As a highly
sensitive substance, pneuma pervades the body establishing a mechanism
able to detect sensory information and transmit the information to the
central commanding portion of the soul in the chest. The information
is then processed and experienced. The Stoics analyzed the activities
of the mind not only on a physical level but also on a logical level.
Cognitive experience was evaluated in terms of its propositional
structure, for thought and language were closely connected in rational
creatures. The Stoic doctrine of perceptual and cognitive presentation
(phantasia) offered a way to coherently analyze mental content and
intentional objects. As a result of their work in philosophy of mind
the Stoics developed a rich epistemology and a powerful philosophy of
action. Finally, the Stoics denied Plato's and Aristotle's view that
the soul has both rational and irrational faculties. Instead, they
argued that the soul is unified and that all the faculties are
rational concluding that the passions are the result not of a distinct
irrational faculty but of errors in judgement.

1. Introduction

Greek and Roman philosophers did not recognize philosophy of mind as a
distinct field of study. However, topics now considered central to
philosophy of mind such as perception, imagination, thought,
intelligence, emotion, memory, identity, and action were often
discussed under the title Peri psychês or On the Soul. This article
surveys some of the ideas held by the ancient Stoics addressing the
soul and related topics which roughly correspond to themes prevalent
in contemporary philosophy of mind and philosophical psychology.
a. Philosophy of Mind and the Parts of Philosophy

The ancient Greek concept of soul differs in many ways from the modern
(post-Cartesian) idea of mind. Contemporary thinkers tend to sharply
contrast the mind and body. When we think of mind we think primarily
of cognitive faculties and perhaps our sense of identity. The Greek
concept of the soul is much broader and more closely connected to
basic bodily functions. The soul is first and foremost the principle
of life; it is that which animates the body. Although the soul
accounts for our ability to think, perceive, imagine, and reason, it
is also responsible for biological processes such as respiration,
digestion, procreation, growth, and motion. Perhaps the closest we
come to a Cartesian concept of the soul in ancient Greek thought would
be Plato, the Pythagoreans, and their successors. Stoic psychology
represents the other end of the spectrum: a corporeal or physicalist
model of soul.

Since there is no clear subject in Stoicism corresponding to
contemporary philosophy of mind, evidence must be gleaned from various
departments of the Stoic philosophical system. The Stoics divided
philosophy into three general "parts": Physics, Logic, and Ethics.
Teachings regarding the soul can be found in all three parts. In
physics the Stoics analyzed the substance of the soul, its
relationship to God and the cosmos, and its role in the functioning of
the human body. In logic the Stoics developed a theory of meaning and
truth, both of which are dependent upon a theory of perception,
thinking, and other psychological concepts. Here the Stoics developed
a sophisticated theory of mental content and intentionality and
wrestled with the ontological ramifications of such a theory. Finally,
in ethics the Stoics developed a complex theory of emotion and a
psychology of action that ultimately had a great impact on their moral
philosophy. The development of one's cognitive faculties was believed
to be inseparable from ethics. In short, Stoic psychology was central
to Stoicism as a whole.
2. Philosophy of Mind and Stoic Physics
a. The Substance of the Soul

Zeno of Citium (335-263 BCE), the founder of Stoicism, was very
interested in the nature of the soul. He and his protégé Cleanthes
(331-232 BCE) emphasized the active nature of the mind by identifying
it as an internal fire or vital heat. It was not until Chrysippus (c.
280-207 BCE) that Stoic psychology reached its mature state. According
to Chrysippus, the human soul consists of a breath-like substance
called pneuma. Cognitive faculties were identified with the specific
activities of the pneuma. In addition to being the substance of the
particular souls of living organisms, pneuma was also held to be the
organizing principle of the cosmos, that is, the world-soul. The
Stoics identified this world-soul with God or Zeus. One source
described God as an intelligent, artistic fire that systematically
creates the cosmos as it expands; in the same passage God is called a
pneuma that pervades the whole cosmos as the human soul pervades the
mortal body. In contrast to contemporary physics and cosmology, the
Stoics saw the world as a living organism.

Stoic psychology is inseparable from Stoic physics and cosmology. The
pneuma of the human soul (pneuma psychikon) is said to be a mixture of
air and fire. Some Stoics saw this soul as a literal mixture of fire
and air, others associated it with a refined fire (similar to aether)
or vital heat. The pneuma permeating the body was held to be a portion
of the divine pneuma permeating and directing the cosmos. The human
soul is a portion of God within us, both animating us and endowing us
with reason and intelligence.

The Stoics argued that the soul is a bodily (corporeal) substance.
Although the soul is a body, it is best to avoid calling Stoic
psychology materialist. The Stoics contrasted soul and matter. For
this reason scholars generally prefer to call Stoic psychology
corporealist, physicalist, or vitalist. Matter is but one of two
principles underlying every bodily substance. These two principles are
the active [to poioun] and the passive [to paschon]. Matter is
identified with the passive principle. Its complement, the active
principle, is reason [logos] or God and is held to extend through
matter providing it with motion, form, and structure. Both principles
are bodily or corporeal principles (that is, they occupy space and are
causally efficient) but neither exists in isolation. Substances can be
dominated by either principle; the more active the substance, the more
rational and divine it is; the more passive, the more material.

The Stoics also made a distinction between principles [archai] and
elements [stoicheia]. The basic elements are earth, water, air, and
fire. Earth and water are heavy, passive elements, dominated by the
passive principle. Air and fire, on the other hand, are active and
closely connected with sentience and intelligence. The Stoics held
that the soul is nourished from the exhalations from the passive
elements. Biological bodies are distinguished from non-biological
bodies by the presence of a specific kind of activity associated with
the presence of the active elements in the body.
b. Pneuma and Tension, and the Scala naturae

Pneuma was the central theoretical tool of both Stoic physics and
Stoic psychology. In contrast to the atomists, the Stoics argued for a
continuum theory which denied the existence of void in the cosmos. The
cosmos was seen as a single continuum of pneuma-charged substance.
Qualitative difference between individual substances, such as between
a rock and a pool of water, is determined by the degree of the
tensional motion of the pneuma pervading the substance. Tensional
motion [tonikê kinêsis] seems to be the motion of the pneuma in a body
that simultaneously moves from the center to the surface and from the
surface back to the center. Passive elements (earth and water) and
dense bodies have a low degree of tensional activity, while active
elements (fire and air) and the soul were seen to possess a high level
of tensional motion. The Stoics organized all natural substances into
different classes based on a hierarchy of powers or a scala naturae.
The concept of tensional motion allowed the Stoics to have a unified
physical theory based on pneuma, while at the same time having one
that distinguished and explained the difference between organic and
inorganic substances. Consequently Stoic physics showed that there
exists a physical connection and continuity between mind and matter.

The Stoic scala naturae is a hierarchy of the powers in nature based
on the activity and organization of the pneuma. Pneuma at its lowest
level of organization and concentration produces simple cohesion in
the matter in which it dwells; it holds together individual unified
bodies. This state of cohesion and coherence is called hexis [cohesive
state]. Bodies hold together on account of an internal flow of pneuma
that begins at the center of the object extending to the surface and
flowing back upon itself producing a tension from a two-way motion.
Hence, even the most stable object possesses internal motion according
to the Stoics. Wood and stones are example of things which possess
hexis.

When the pneuma in a body is organized with a greater degree of
activity, there is phusis or organic nature. Things that have phusis
grow and reproduce but do not show signs of cognitive power. The
pneuma that produces phusis also provides the stability or cohesion of
hexis. The Stoics held that each power on this scala naturae subsumes
the power below it. Plants are obvious examples of organisms that have
both hexis and phusis but not soul.

The next tier of this hierarchy of pneumatic activity is soul [
psuchê]. The characteristic marks of this level of organization are
the presence of impulse and perception. Non-rational animals have
hexis [cohesive state], phusis [an organic nature], and psuchê [soul].

Only human beings and gods possess the highest level of pneumatic
activity, reason [logos]. Reason was defined as a collection of
conceptions and preconceptions; it is especially characterized by the
use of language. In fact, the difference between how animals think and
how humans think seems to be that human thinking is linguistic — not
that we must vocalize thoughts (for parrots can articulate human
sounds), but that human thinking seems to follow a syntactical and
propositional structure in the manner of language. The Stoics
considered thinking in rational animals as a form of internal speech.

The Stoic hierarchy of pneuma should not be confused with Aristotle's
theory of the hierarchy of the soul to which there is some
resemblance. While the Stoic scala naturae explains both organic and
inorganic substances, Aristotle's hierarchy is limited to biological
organisms. Aristotle's theory is also based on a very different idea
of soul.

The physical theory underlying Stoic psychology has some rather
startling implications. For example, the Stoics held that active
substances could pervade passive substances. Hence the soul, which is
a body, is able to pervade the physical body. The soul does not
pervade the body like the water in a sponge, that is, by occupying
interstitial spaces; rather, the Stoics held that the corporeal pneuma
occupied the exact same space as the passive matter, that is, both
substances are mutually coextended [antiparektasis]. The soul
permeates the body in the same way as heat pervades the iron rod,
occupying the same space but being qualitatively distinct. The Stoics
called this sort of mixture crasis or total blending.

Total blending should be contrasted with particulate mixture and
fusion mixture. An example of a particulate mixture is the mixture of
different kinds of seeds. Each seed remains unaffected by the mixture,
only the distribution is altered. This is sometimes called
juxtaposition. Fusion mixture occurs when the items mixed are
physically altered and a new, single substance emerges. Once eggs,
milk, yeast, and flour are mixed together a new substance is produced
(bread). In contrast to fusion mixture, in total mixture or crasis the
blended substances (such as water and wine) were held to retain their
properties and in principle could be separated.

A particular and highly controversial characteristic of total blending
is that for mutual coextension to occur, it is not necessary that both
bodies be of the same in quantity. Thus Chrysippus provocatively
claimed that in total blending a drop of wine could pervade (coextend
through) the entire ocean. This is an explicit rejection of
Aristotle's theory of mixture in De generatione et corruptione. The
pneuma in active substances seems to have great elasticity and is able
to exist in a very rarified form while maintaining distinct
properties.
c. Death

The doctrine of pneuma and total blending allowed the Stoics to adopt
Plato's definition of death as "the separation of the soul from the
body." The Stoics, however, used this definition against Plato,
arguing that since only physical things can separate from physical
things, the soul must be corporeal. Since the soul pervades the body
as a crasis type mixture, separation is possible. The separation seems
to occur by a loosening of the tension of the soul. Sleep is said to
be a kind of mild relaxing, whereas death is a total relaxing of the
tension which results in the departure of the soul from the body.

Dying is not the end of a person's existence, according to the Stoics.
Once the soul has separated from the body it maintains its own
cohesion for a period of time. Chrysippus and Cleanthes disagreed
regarding the fate of the soul after death. Cleanthes held that the
souls of all men could survive until the conflagration, a time in
which the divine fire totally consumes all matter. Chrysippus, on the
other hand, held that only the souls of the wise are able to endure.
The souls of the unwise will exist for a limited time before they are
destroyed or reabsorbed into the cosmic pneuma. The souls of
irrational beasts are destroyed with their bodies. In no case is there
any indication that the survival of the soul after death had any
direct benefit to the individual or that the Stoics used this as a
motivator toward ethical or intellectual behavior. There is no heaven
or hell in Stoicism; the time to live one's life and to perfect one's
virtues is in the present.
d. The Parts of the Soul

The pneuma of the soul has a specific structure which helps account
for its capacities. The Stoics held that the soul consists of eight
parts which are spatially recognized portions or streams of pneuma.
The eight parts of the soul are the five senses (sight, vision, smell,
taste, touch), the reproductive faculty, the speech faculty, and the
central commanding faculty [hêgemonikon]. All of the parts of the soul
can be seen as extensions of pneuma originating in the hêgemonikon.
Several analogies were employed to explain the structure of the soul:
the soul is like an octopus, a tree, a spring of water, and even a
spider's web. The analogies of the octopus, tree, and spring emphasize
the unity of the soul and the idea that the individual powers or
faculties are rooted in or sprout from the hêgemonikon in the heart.
The Stoics, like Aristotle and Praxagoras of Cos, believed that the
cognitive center is in the chest and not the head. These analogies are
also consistent with Stoic views on embryological development; for the
Stoics recognized that the heart is the first functioning organ of the
fetus and held that the pneuma of the soul begins in the heart of the
fetus and extends through the body, refining its powers as the fetus
grows. The powers of sense perception, speech, and reproduction are
extensions of the pneuma of the hêgemonikon which reaches its mature
state as the child approaches adulthood.

Some have compared the Stoic contrast between the commanding faculty
and the distal faculties to the modern distinction between the central
and peripheral nervous systems. This comparison can be justified by
the fact that the Stoics held that the higher cognitive functions and
all cognitive experience take place exclusively in the hêgemonikon .
While Aristotle seemed to be comfortable with attributing the
experience of touch to the flesh and sight to the eyes, the Stoics
tell us that the senses merely report the information to the central
faculty where it is experienced and processed.

The idea of sensation as the transmission [diadosis] of sensory
information is illustrated in the final two analogies of the soul. The
first states that activity of the soul is like a king who sends out
messengers. When the messengers acquire information they report it
back to the king. Likewise, the hêgemonikon extends its pneuma to the
sense organs, and when these in turn acquire sensory information, the
pneuma transmits the information back to the heart. The second analogy
states that the soul is like a spider in a web. When the web is
disturbed by an insect the movement is transmitted through vibrations
to the spider sitting at the center. The human soul in a like manner
extends through the body like a sensory grid establishing a sensory
tension [tonos]. All perceptual information is transmitted by a
tensional motion [kinesis tonikê]. In the case of the senses of
hearing and sight, the external medium between the sense organs and
the sense object operates as an extension of the soul-pneuma. Air also
contains a degree of tension which a sound disturbs like a pebble
tossed into a calm pool; the sound is transmitted through the air and
sends the auditory information in a spherical pattern. Once the
tensional motion of the sound reaches the ears, the sound pattern is
picked up by the pneuma of the body which in turn transmits the
information to the hêgemonikon . Vision works similarly; the pneuma
from the eyes interacts with external light to establish a cone shaped
visual field. This tensed field can detect the shapes of the objects
within as though by touch. Indeed all of the senses were thought to be
forms of touch. Color was held to be a sort of surface texture on the
object; apparently the Stoics held that each color had its own pattern
of disturbance in the visual pneuma.

These analogies capture the relationship between the commanding
faculty and the senses; they do not as effectively capture or explain
the remaining two distal faculties: speech and reproduction. Whereas
the senses are passive insofar as they receive the tensional motion of
a sense object and communicate it to the command center, in the case
of speech and reproduction the motion goes in the opposite direction.
Speech is an expression and articulation of the tensional motion
produced by the construction of thought in the hêgemonikon.
Interestingly, it is the fact that speech is produced in conjunction
with breath that Chrysippus used as a central argument for the
location of the hêgemonikon in the heart and not the brain. Little
survives on how the Stoics viewed the relationship between the
commanding faculty and the reproductive faculty. Sources do tell us
that seminal information which produces the child is drawn from the
entire body of both parents; this is in contrast to the Aristotelian
claim that the male parent contributes the form and the female the
matter.

In addition to the eight parts of the soul, the human hêgemonikon
itself was characterized by four basic powers: presentation
[phantasia], impulse [hormê], assent [sugkatathesis], and reason
[logos]. Iamblicus tells us that the eight parts of the soul differ in
bodily substrata while the four powers of the hêgemonikon must be
individuated by quality in regards to the same. In other words, the
four powers of the hêgemonikon are not individually isolated in space;
their identity seems to be characterized exclusively by their
function.
3. Philosophy of Mind and Stoic Logic
a. Presentation (phantasia), Memory, and Concept Formation

The most basic power of the hêgemonikon is the ability to form
presentations [phantasiai]. Other psychological states and activities
such as mental assent, cognition, impulse, and knowledge are all
either extensions or responses to presentations. Zeno defined a
presentation as an imprinting [tupôsis] in the commanding faculty. He
suggested that the soul is imprinted by the senses much in the same
way as a signet ring imprints its shape in soft wax. At birth the
hêgemonikon is said to be like a blank sheet of paper which is ready
to receive writing; all our cognitive experience is drawn either
directly or indirectly from sense experience, that is, empirically.
Zeno held that the term phantasia comes from the word for light
[phôs]. Like light, the presentation is said to reveal itself and its
cause. Although few agree with his etymology, the report shows that
Zeno saw the phantasia as containing two elements: the phenomenal
experience of its object and the representational content (i.e. it
represents an object in the world). The Stoics sometimes called the
phantasia an affection [pathos] in the soul; this seems to emphasize
that there is a qualitative experience inseparable from the
representational information. When we see a red circle, we don't just
acquire information, we also experience it as a red circle.

Chrysippus was not comfortable with the imprint analogy that Zeno and
Cleanthes employed. Taken literally the analogy fails to capture the
complexity of mental content. What kind of imprint would a color or
sound make? How could the pneuma within the chest maintain and store
such a rich collection of patterns and information? Chrysippus
suggested that the imprinting metaphor must be abandoned and instead
preferred to call presentations "alterations" [alloiôsis or
heteroiôsis] of the hêgemonikon . He stated that just as the same air
can be simultaneously altered by many sounds, maintaining each, so the
hêgemonikon could retain such diverse and complex information.
Although this is a far from satisfying solution, we should remember
that contemporary philosophy of mind still has much work to do in
explaining memory and concept retention.

The Stoics distinguished presentations drawn directly from the senses
[aisthetike phantasiai] and those which are produced by the mind from
previously experienced phantasiai. The doctrine of presentation also
provided the foundation for a theory of memory and concept formation.
Memory was seen to be stored phantasiai. Conceptions [ennoêmata] on
the other hand seemed to be collections or patterns of stored
phantasiai. The Stoic theory is flexible enough to account for real
and fictional (intentional) objects, thereby establishing a plausible
theory of imagination. The Stoics distinguished between phantasia,
phantaston, phantastikon, and phantasma. The phantaston is the object
producing the phantasia. A phantastikon is a phantasia which does not
come from a real object, such as those produced by the imagination.
Imagination was explained as the manipulation of mental content. By
taking elements from stored experience and enlarging, shrinking,
transposing, or negating parts of the phantasiai it is possible
imagine monsters; thus one can produce mental content which has no
real object. For example we can create a mermaid by transposing a body
of a fish onto a young woman's torso. Although mermaids and monsters
don't exist, we need to explain how non-existing things can be the
object of thought and even produce desire or attraction. The Stoics
did this by drawing a distinction between the imagined object
(phantasma), i.e. the mermaid, and the mental construct
(phantastikon), the thought of the mermaid. We are not attracted to
the idea or mental image of the mermaid but to the intentional object
of the idea, namely to the mermaid herself. Similar distinctions were
pursued in the early 20th century by philosophers such as Meninong and
Russell.

The Stoics made a further distinction in their doctrine of
presentations: some presentations are rational, some are not. Rational
presentations are limited to human beings and are said to be
"thoughts" [noeseis]. Thoughts, like other phantasiai, are physical
states of the soul-pneuma. The characteristic feature of a rational
presentation seems to be its structure or syntax. Something is said
about something, and consequently the thought now has meaning — and if
it is a proposition, it has a truth value associated with it. Simple
thoughts, when expressed in language, have three elements: the object
(thing signified), the sound (the signifier), and the
linguistic/mental content (what is said). For example, in the sentence
"The cat is black" the thing signified is the black cat; the signifier
is the sounds of the words uttered; and finally the thing signified is
the content of what is being said, namely, the claim regarding the
color of a specific animal. The latter, the intelligible content of
the statement, is called a lekton which is said to subsist with the
rational presentation or thought; it is the content which is either
true or false, not the object or the sound. A lekton is not a
corporeal entity like a thought or the soul; it seems to be a
theoretical entity which loosely corresponds to the contemporary
notion of a proposition, a statement, or perhaps even the meaning of
an utterance. It is the lekton that makes the sounds of a sentence to
be more than just sounds. The doctrine of the lekta has generated much
controversy in current scholarship and is recognized to be an
important link between Stoic theory of mind and Stoic logic.
b. Impulse, Assent, and Action

Although we may entertain and experience all sorts of presentations,
we do not necessarily accept or respond to them all. Hence the Stoics
held that some phantasiai receive assent and some do not. Assent
occurs when the mind accepts a phantasia as true (or more accurately
accepts the subsisting lekton as true). Assent is also a specifically
human activity, that is, it assume the power of reason. Although the
truth value of a proposition is binary, true or false, there are
various levels of recognizing truth. According to the Stoics, opinion
(doxa) is a weak or false belief. The sage avoids opinions by
withholding assent when conditions do not permit a clear and certain
grasp of the truth of a matter. Some presentations experienced in
perceptually ideal circumstances, however, are so clear and distinct
that they could only come from a real object; these were said to be
kataleptikê (fit to grasp). The kataleptic presentation compels assent
by its very clarity and, according to some Stoics, represents the
criterion for truth. The mental act of apprehending the truth in this
way was called katalepsis which means having a firm epistemic grasp.

The idea of katalepsis as a firm grasp reappears in Zeno's famous
analogy of the fist. According to Cicero, Zeno compared the phantasia
to an open hand, assent, to a closing hand, the katalepsis, to a
closed fist, and knowledge to a closed fist grasped by the other hand.
Zeno's analogy however may be a little misleading if the reader
assumes there to be a temporal succession and a series of discreet
processes. Other evidence indicates that this is not the point of the
analogy. For example, katalepsis was defined as a kind of assent, not
as a discrete post-assent process. A katalepsis is an assent to a
kataleptic presentation. Moreover knowledge [epistemê] was defined as
a katalepsis that is secure and unchangeable by reason. The point of
the fist analogy then seems to be that the central powers of the
commanding faculty have different and progressively greater epistemic
weight. The analogy emphasizes the epistemic progression from simple
presentations to the systematic coherence of knowledge (it being
confirmed by and consistent with other katalepseis); the analogy is
not fundamentally about the discreteness of the psychological powers.

The emphasis on assent in Stoic psychology and epistemology is an
important contribution to ancient philosophy. The Stoics used assent
to indicate that a phantasia had been accepted by the mind. It also
allows the agent to entertain a cognition while at the same time
reject it. Indeed, philosophical prudence often demands that we
withhold assent in cases of doubt. The introduction of assent as a
distinct process provided a plausible way to explain how an agent may
entertain a specific thought without necessarily accepting it.

In addition to epistemology, assent plays an important role in the
Stoic theory of action. Presentational content often provokes an
inclination to act by representing something as desirable. This kind
of presentation was called phantasia hormetikê or impulse-generating
presentation and was held to produce an impulse to act. The impulse is
therefore a sort of call to action which is manifested as a motion of
pneuma directed toward the specific organs of action.

The basic function of impulse is to initiate motion. When we perceive
an object or event in the physical world, a phantasia or presentation
is produced in the commanding faculty which is then evaluated by the
rational faculty. Depending on the content of the presentation and the
individual's conception of what is good, the object of perception may
be classified as good, evil, or indifferent. Thefaculty of assent in
conjunction with reason will accept, reject, or withhold judgement
based on the value of the object. If the object is deemed good, an
impulse is initiated as a kind of motion in the soul substratum. If
the object is bad, repulsion [aphormê] is produced, and the agent
withdraws from the object under consideration.
4. Philosophy of Mind and Stoic Ethics
a. Primary Impulse and Prolepsis

We have seen that the Stoics held that at birth the soul is free of
experiential content. The Stoics, however, did not hold that this
excluded the possibility that we are born with innate characteristics
and psychological impulses. The most basic impulse found in new-born
creatures is the impulse toward self-preservation. This is the primary
human impulse and the starting point of Stoic ethics. This impulse is
implanted by Nature and entails a certain consciousness of things
appropriate to (or belonging to) the organism and of things alien or
hostile to the creature. In contrast to the Epicureans, who held that
the primary impulse was toward pleasure, the Stoics argued that the
innate impulse toward self-regard and an awareness of one's own
constitution was even more elementary. This innate impulse explains
how animals naturally know how to use their limbs and defensive organs
and why it is that animals naturally recognize predators as enemies.

Children and animals, however, are not rational; Nature must therefore
supply the primary impulse as a foundation for behavior. In the case
of animals the innate impulses explain a range of complex behavior,
which in many cases appears intelligent. For example, the Stoics held
that a spider does not possess rationality despite the apparently
intelligent use of a web to catch insects. Primary impulses in animals
are therefore identified with complex instincts. In the case of human
beings, primary impulse is ideally a transitional mechanism. As
children mature into adults, they develop rationality so that the
impulse toward self-preservation falls under the scrutiny of reason.
Rationality permits the agent to develop the notion of duty and
virtue, which may at times take precedence over self-preservation. As
the agent progresses in virtue and reason, children, family members,
neighbors, fellow citizens, and finally all humankind are likewise
seen as intrinsically valuable and incorporated into the agent's
sphere of concern and interest. This process is called oikeiôsis or
the doctrine of appropriation and is central to the Stoic ethics.

Also closely associated with the doctrine of the primary impulse is
the Stoic doctrine of preconception [prolepsis]. A preconception is an
innate disposition to form certain conceptions. The most frequently
mentioned preconceptions are the concept of the good and the concept
of God. Since the Stoics held that the soul is a blank sheet at birth,
the preconception cannot be a specific cognition but only an innate
disposition to form certain concepts.
b. Passion and Eupatheia

The final element of Stoic philosophy of mind to be presented in this
article is the doctrine of the passions. Plato and Aristotle held that
the soul had both rational and irrational parts and used this view to
explain mental conflict. For example, the irrational "appetitive part"
of the soul may desire a steady diet of rich and fatty foods. The
rational part of the soul, however, will resist the demands of the
irrational part since such a diet is unhealthy. The result is
emotional conflict and in somecases moral conflict. Most Stoics
(Posidonius being the most famous exception), in contrast, denied the
existence of an irrational faculty. However, in order to explain the
phenomenon of mental conflict, the Stoics developed a theory of
passion which they believed could do the same work as Plato's or
Aristotle's.

The Stoics defined passion in several ways, each emphasizing a
different facet of the term. The four most common accounts or
definitions of passion are:

1. An excessive impulse.
2. An impulse disobedient to (the dictates of) reason.
3. A false judgement or opinion.
4. A fluttering [ptoia] of the soul.

Each definition emphasizes a different aspect of passion. The first
two definitions tell us that a passion is a kind of impulse. The first
of these focuses on force. A passion is a runaway impulse or emotion.
Chrysippus compared a passion to a person running downhill and unable
to stop at will. The soul is carried away by the sheer force and
strength of the impulse. Passions often develop a momentum that cannot
easily be stopped. Some texts also emphasize that there is a temporal
dimension to passion. The fresher the passion, the stronger the
impulse; passions usually weaken over time.

The second and third definitions emphasize the logical side of
passion. Passions are unruly and contrary to reason. They are based on
mistaken thinking or false opinions. The fact that passions are
irrational does not mean that they come from an irrational faculty.
They can be errors produced by the rational faculty. Having a rational
faculty does not imply infallibility. Rather, it implies that
cognitive states are produced through an inferential process which
operates with a syntax similar to language. Mathematics operates in a
similar fashion. When we make mathematical errors, we do not appeal to
a non-mathematic part of the soul which conflicts with the
mathematical. Rather we attribute the error to a single, though
limited and fallible, rational faculty. The Stoics saw passion in the
same way. Passions are false judgements or mistakes in regards to the
value of something and are thereby misdirected impulses. According to
Stoic ethics, only virtues are truly good, whereas externals such as
wealth, honor, power, and pleasure are indifferent to our happiness
since each can also harm us and each ultimately lies beyond our
control. These externals then are said to be morally "indifferent"
(adiaphoron). When we mistakenly value something indifferent as though
it were a genuine good, we form a false judgement and experience
passion.

The traditional Stoic passions can be broken down into four different
kinds or classes of errors in judgement. These errors concern the good
and bad (value), and the present and the future (time):
Present Future
Good Pleasure Appetite
Bad Distress Fear

When one identifies something as good in the present when in fact it
is not truly a good we have the passion called pleasure and its
subspecies. When we do the same in the future we have appetite.
Likewise when we misidentify something as bad in the present, we
experience the passion called distress; when we err regarding
something in the future we call it fear.

The fourth and final definition of passion as "a fluttering in the
soul" is most likely a physical description of passion much as
Aristotle describes anger as a boiling of blood around the heart. As
corporealists, the Stoics frequently described activities as physical
descriptions of the pneuma of the soul. The Stoics defined the
individual passions as an irrational swelling or rising [heparsis].
When our impulses are excessive and unruly, the pneuma in one's chest
canfeel like a fluttering. In contrast, Zeno described happiness, a
state which presupposed rationality and virtue, as a smooth flowing
soul. The fluttering may also signify the instability of passions as
judgements. Chrysippus illustrated emotional disruption caused by the
fluttering of passion with the example of Euripides' Medea, who
continually flipped back and forth from one judgement to another.

These four definitions or descriptions of passion are in agreement
though each emphasizes a different aspect of passion. For example,
grief over lost or stolen property is considered a passion, a species
of distress. Since the object of concern (the stolen property) is in
truth of no moral worth (indifferent), for it is only our virtuous
response to the situation that qualifies as morally good or bad, the
impulse identified with the grief is excessive (1). Since we do not
heed reason which would tell us that happiness lies in virtue alone,
it is also an impulse disobedient to reason (2). Likewise, since the
value attributed to an object does not represent its true worth, it is
a false judgement (3). Finally, the distress which we experience in
the grief manifests itself not as a smooth calm state but as a
fluttering or disturbance in our soul (4).

If passions are excessive impulses and mistaken judgements resulting
in emotional disquietude, there must also be appropriate impulses and
correct judgements resulting in emotional peace. It is a mistake to
assume that if the Stoics reject passion that they seek a life void of
any emotion, that is, that they seek to be emotionally flat. A better
reading of Stoicism is that the goal is not absence of emotion, but a
well-disposed emotional life. This is a life in which impulses are
rational, moderate, and held in check. It is a state in which one's
impulses are appropriate to and consistent with the nature of things,
both regarding the truth of the judgement and the degree of the
response. This view is supported by the Stoic doctrine of the
eupatheiai. Calling positive emotions "good-passions" may have been an
attempt to rectify the misrepresentation of their school as being void
of emotion. Examples of the eupatheiai are joy [khara], caution
[eulabeia], and reasonable wishing [boulêsis]. Joy is said to be the
counterpart of pleasure, caution is contrasted with fear, and
reasonable wishing is contrasted with appetite. The difference is that
in the eupatheiai the force of the impulse is appropriate to the value
of the object, the impulse is consistent with rational behavior, and
finally the belief or judgement regarding the nature of the object is
true.

One should note that there are only three categories for the
eupatheiai in contrast to the four for passions [é]. There is no
eupatheia corresponding to distress. This is due to the Stoic
conception of moral invincibility. Distress was defined as an
incorrect judgement regarding a present evil. The Stoics, however,
held that the good lies not in external events or objects but in the
virtuous response of the moral agent to any situation. Since it is
always possible to respond virtuously, there is no true evil in the
present. The good is always possible here and now.
5. References and Further Reading
a. Collections of Stoic texts

* Clark, Gordon H. (ed.). 1940. Selections From Hellenistic
Philosophy. New York: Croft.
* Edelstein, L. and Kidd, I. G. (eds.) 1972. Posidonius. The
Fragments, 4 vols. Cambridge: University Press.
* Hülser, Karlheinz. (ed.). 1987. Die Fragmente zur Dialektik der
Stoiker. 4 vols. Stuttgart: Frommann-Holzboog.
* Inwood, Brad and Gerson, L. P. (eds.). 1997. Hellenistic
Philosophy: Introductory Readings, 2nd edition. Indianapolis: Hackett.
* Long, A.A. and Sedley, D.N. (eds.). 1987. The Hellenistic
Philosophers, 2 vols. Cambridge: Cambridge University Press.
* Saunders, Jason L. (ed.). 1996. Greek and Roman Philosophy after
Aristotle. New York: Free Press.
* von Arnim, Ioannes (ed.). 1903-1905. Stoicorum Veterum
Fragmenta. Leipzig: Teubner.

b. Recommended Readings on Stoic Psychology

* Algra, Keimpe, et al. (eds.) 1999. The Cambridge History of
Hellenistic Philosophy. Cambridge: Cambridge University Press.
* Annas, Julia. 1992. Hellenistic Philosophy of Mind. Berkeley:
University of California Press.
* Arthur, E. P. 1983. "The Stoic analysis of the mind's reaction
to presentations", Hermes 111: 69-78.
* Brennan, Tad. 1996. "Reasonable Impressions in Stoicism",
Phronesis 41.3: 318-334.
* _____. 1998. "The Old Stoic Theory of Emotion", in Sihvola and
Engberg-Pedersen (eds.) 1998: 21-70.
* Brunschwig, Jacques. 1986. "The cradle argument in Epicureanism
and Stoicism", in Schofield and Striker 1986: 113-144.
* _____. 1994. Papers in Hellenistic Philosophy. Cambridge:
Cambridge University Press. Translated by Janet Lloyd.
* Brunschwig, J. and Nussbaum, M. C. (eds.) 1993. Passions &
Perceptions: studies in Hellenistic philosophy of mind. Proceedings of
the Fifth Symposium Hellenisticum. Cambridge: Cambridge University
Press.
* Caston, Victor. 1999. "Something and Nothing: The Stoics on
concepts and universals" Oxford Studies in Ancient Philosophy 17:
145-213.
* Chiesa, M. C. 1991. "Le problème du langage intérieur chez les
Stoïciens", Revue Internationale de Philosophie 3, 301-321.
* Cooper, John. 1998. "Posidonius on Emotions", in Sihvola and
Engberg-Pedersen, 1998: 71-112.
* Doty, Ralph. 1992. The Criterion of Truth. American University
Studies. Series V Philosophy, vol. 108. New York: Peter Lang.
* Engberg-Pedersen, Troels. 1998. "Marcus Aurelius on Emotions",
in Sihvola and Engberg-Pedersen, 1998: 305-338.
* Everson, Stephen. 1990. Epistemology. Companions to Ancient
Thought. Vol. 1. Cambridge: Cambridge University Press.
* _____. 1991. Psychology. Companions to Ancient Thought. Vol. 2.
Cambridge: Cambridge University Press.
* _____. 1994. Language. Companions to Ancient Thought. Vol. 3.
Cambridge: Cambridge University Press.
* Frede, Michael. 1983. "Stoics and Skeptics on clear and distinct
impressions", in Essays in Ancient Philosophy. Minneapolis: University
of Minnesota.: 65-93.
* _____. 1994. "The Stoic notion of lekton", in Everson 1994: 109-128.
* Gill, Christopher. 1991. "Is there a concept of person in Greek
philosophy?", in Everson 1991: 166-193.
* _____. 1998. "Did Galen Understand Platonic and Stoic Thinking
on Emotion", in Sihvola and Engberg-Pedersen, 1998: 113-148.
* Glibert-Thirry, A. 1977. "La théorie stoïcienne de la passion
chez Chrysippe et son évolution chez Posidonius", Revue philosophique
de Louvain 75: 393-435.
* Gould, J. 1970. The Philosophy of Chrysippus. Leiden: Brill.
* Hahm, David E. 1977. The Origins of Stoic Cosmology. Columbus:
Ohio State University Press.
* _____. 1978. "Early Hellenistic theories of vision and the
perception of color", in Machamer & Turnbull 1978: 60-95.
* Imbert, Claude. 1978. "Théorie de la representation et doctrine
logique dans le stoicisme ancien", in Brunschwig 1978: 223-249.
* Ingenkamp, Heinz Gerd. 1971. "Zur stoischen Lehre vom Sehen",
Rheinisches Museum für Philologie 114: 240-246.
* Inwood, Brad. 1985. Ethics and Human Action in Early Stoicism.
Oxford: Clarendon Press.
* _____. 1993. "Seneca and psychological dualism", in Brunschwig
and Nussbaum 1993: 150-183.
* _____. 1999. "Rules and Reasoning in Stoic Ethics", in Topics in
Stoic Philosophy, Ierodikonou, Katerina (ed.): 95-127.
* Ioppolo, Anna-Maria. 1990. "Presentation and assent: A physical
and cognitive problem in early Stoicism", Classical Quarterly 40:
433-449.
* Kerferd, George B. 1978. "The search for personal identity in
Stoic thought", Bulletin of the John Ryland Library 55: 177-196.
* _____. 1978. "The problem of synkathesis and katalepsis in Stoic
doctrine", in Brunschwig 1978: 251-272.
* Kidd, I.G. 1971. "Posidonius on Emotions" in Long 1971: 200-215.
* Lesses, Glenn. 1998. "Content, Cause, and Stoic Impressions",
Phronesis 43.1: 1-25.
* Lewis, Eric. 1995. "The Stoics on identity and individuation",
Phronesis 40: 89-108.
* Lloyd, A.C. 1978. "Emotion and decision in Stoic psychology", in
Rist 1978: 233-246.
* Long, A. A. (ed.). 1971. Problems in Stoicism. London: Athlone Press.
* _____. 1971. "Language and thought in Stoicism", in Long 1971: 75-113.
* _____. 1974. Hellenistic Philosophy. 2nd ed. London: Duckworth.
* _____. 1978. "The Stoic distinction between truth and the true",
in Brunschwig 1978: 297-315.
* _____. 1982. "Soul and Body in Stoicism", Phronesis 27: 34-57.
* _____. 1991. "Representation and the self in Stoicism", 102-120
in Everson 1991.
* Nussbaum, Martha. 1993. "Poetry and the passions: two Stoic
views" in Brunschwig and Nussbaum 1993: 97-149.
* _____. 1994. The Therapy of Desire: Theory and Practice in
Hellenistic Ethics. Princeton, NJ: Princeton University Press.
* Modrak, Deborah K. 1993. "Stoics, Epicureans and mental
content", Apeiron 26: 97-108.
* Ostenfeld, Erik. 1987. Ancient Greek Psychology and the Modern
Mind-Body Debate. Aarhus, Denmark: Aarhus University Press.
* Pembroke, S. G. 1971. "Oikeiôsis", in Long 1971: 114-149.
* Reale, Giovanni. 1990. A History of Ancient Philosophy, vol. 4.
The Schools of the Imperial Age. Albany, NY: State University of New
York Press. [Edited. & translated by John R. Catan].
* Reesor, Margaret, E. 1989. The Nature of Man in Early Stoic
Philosophy. London: Duckworth.
* Rist, John M. 1969. Stoic Philosophy. Cambridge: Cambridge
University Press.
* _____. 1985. "On Greek biology, Greek cosmology and some sources
of theological pneuma", Prudentia. The Concept of Spirit.
Supplementary Number 1985, 27-47.
* Rist, John M. (ed.). 1978. The Stoics. Berkeley, Los Angeles,
and London: University of California Press.
* Rorty, Amélie Oksenberg. 1998. "The Two Faces of Stoicism:
Rousseau and Freud", in Sihvola and Engberg-Pedersen, 1998: 243-270.
* Sakezles, Priscilla. 1998. "Aristotle and Chrysippus on the
physiology of human action", Apeiron 31.2, 127-166.
* Sandbach, F. H. 1971. "phantasia kataleptike", in Long 1971: 9-21.
* Schofield, M., Burnyeat, M. and Barnes, J. (eds.). 1980. Doubt
and Dogmatism: studies in Hellenistic epistemology. Oxford: Clarendon
Press.
* Schofield, M. and Striker, G. (eds.). 1986. The Norms of Nature.
Cambridge: Cambridge University Press.
* Sedley, David. 1993. "Chrysippus on psychophysical causality",
in Brunschwig and Nussbaum 1993: 313-331.
* Sharples, R. W. 1996. Stoics, Epicureans, and Sceptics: An
Introduction to Hellenistic Philosophy. London: Routledge.
* Sihvola, Juha and Engberg-Pedersen, Troels (eds.) 1998. The
Emotions in Hellenistic Philosophy. Dordrecht: Kluwer Academic
Publishers.
* Sorabji, Richard. 1990. "Perceptual content in the Stoics",
Phronesis 35, 301-314.
* _____. Animal Minds & Human Morals. Ithaca: Cornell University Press.
* _____. 1998. "Chrysippus – Posidonius – Seneca: A High Level
Debate on Emotion", in Sihvola and Engberg-Pedersen, 1998: 149-170.
* Striker, Gisela. 1996. Essays on Hellenistic Epistemology and
Ethics. Cambridge: Cambridge University Press.
* Todd, Robert B. 1974. "'Synentasis' and the Stoic theory of
perception", Grazer Beiträge 2, 251-261.
* _____. 1976. Alexander of Aphrodisias on Stoic Physics. Leiden: Brill.
* von Staden, Heinrich. 1978. "The Stoic theory of perception and
its 'Platonic' critics", 96-136 in Machamer & Turnbull 1978.
* Watson, Gerard. 1988. "Discovering the imagination: Platonists
and Stoics on phantasia", 208-233 in Dillon and Long 1988.
* _____. 1994. "The concept of 'phantasia' from the late
Hellenistic period to early Neoplatonism", Aufstieg und Niedergang der
Römischen Welt (ANRW) II.36.7: 4765-4810.
* Williams, Bernard. 1994. "Stoic Philosophy and the Emotions:
reply to Richard Sorabji", Aristotle and After, 21-214.