## 1. Preliminaries


### 1.1 The School and its History



The Stoic school was founded around 300 BCE by Zeno of Citium, a
voracious reader of Socratic dialogues, who also studied under the
Cynic Crates and was influenced by the teachings of Plato's
Academy and the Megarian School. The Stoa competed with the school
founded only a little before in Athens by Epicurus, and Stoic and
Epicurean views are often compared and contrasted. Zeno was succeeded
in the leadership of the Stoa first by Cleanthes of Assos and then by
Chrysippus of Soli, who headed the school from around 230 until 206
BCE and was by all accounts its foremost theorist and systematizer.
Following Chrysippus, the position of "scholarch" passed
to his former students, the last of which being Diogenes of Babylon in
the middle of the 2nd century BCE.



Some scholars see this moment as marking a shift in the Stoic school,
from the so-called "Old Stoa" to "Middle
Stoicism", though the relevance and accuracy of this
nomenclature is debated (see Inwood 2022). The latter term is
nonetheless frequently used to encompass the work of Stoic
philosophers in the second and first centuries BCE. A significant
feature of the second century is the sharp and powerful attacks
against Stoic views formulated by the Academic
 Carneades,
 to which Antipater of Tarsus, Diogenes' successor, responded at
length. Diogenes and Antipater also heralded increased engagement with
Platonic (Sedley 2003; Reydams-Schils 1999) and possibly Aristotelian
doctrine, arguably peaking with Panaetius in the second half of 2nd
century BCE and his student Posidonius in the first century BCE. For
developments from Antipater onwards, see Inwood 2022; for the
contributions of Panaetius and Posidonius and their relation to
previous thinkers, see Tieleman 2007.



Stoicism became particularly fashionable in the Roman period. Although
never identifying as a Stoic himself,
 Cicero,
 who studied philosophy in Athens and endeavored to popularize it at
Rome, engaged extensively with Stoic theory in his philosophical works
and modeled his *On Proper Functions* (*De Officiis*) on
Panaetius' treatise of the same name. During the Imperial era,
several prominent public figures were associated with the Stoic
school. Appointed to the court of Emperor Augustus in the late 1st
century BCE was the Stoic philosopher Arius Didymus, and a generation
later
 Seneca
 served as advisor to Nero.
 Epictetus,
 a former slave, was expelled from Rome by Domitian along with other
philosophers in 93 CE, and his works, recorded by his student Arrian,
heavily influenced
 Marcus Aurelius,
 Roman Emperor from 161-180 CE. Also active in the second
century CE was the Stoic philosopher Hierocles, whose detailed
treatise on psychology and ethical theory, *The Elements of
Ethics*, is partially extant (see Ramelli 2009).



Over this remarkable span of time during which the Stoic school
operated in some form or another, evolutions in views and shifts in
focus unsurprisingly took place. The nature and extent of these
intra-school developments and disagreements - some of which we
will consider below - remains the subject of ongoing scholarly
debate.


### 1.2 Systematicity



Stoic philosophy was, from Zeno onwards, conceived of as comprising
three parts: physics (*phusike*), logic
(*logike*), and ethics (*ethike*).
Each of these parts includes a wide array of further topics nowadays
dealt with separately. Logic, for example, includes not only formal
logic, but also questions now typically falling under the remit of
philosophy of language, epistemology, and philosophy of mind. In
addition, all three parts of philosophy were thought by the Stoics to
work together to form an interconnected and coherent system (exactly
how strongly the claim of systematization is to be taken is disputed;
see below). The Stoics emphasized this point with a number of
analogies intended to illustrate how the three parts of philosophy fit
together and form a whole:



> 
> 
> They compare philosophy to a living being, likening logic to bones and
> sinews, ethics to the fleshier parts, and physics to the soul. They
> make a further comparison to an egg: logic is the outside, ethics what
> comes next, and physics the innermost parts; or to a fertile field:
> the surrounding wall corresponds to logic, its fruit to ethics, and
> its land or trees to physics. (Diogenes Laertius, 26B; see our
>  bibliography
>  for a guide to citations in this entry)
> 
> 
> 



The latter two analogies seem to point to the idea that the purpose of
philosophy, according to the Stoics, is to become virtuous, that is,
to attain wisdom and thereby lead the good life, so that the
overarching goal (the crop or the egg white, which the ancients
assumed was nourished by the yolk) is ethical. Nonetheless, the other
parts of philosophy play an essential and necessary part in achieving
this goal, and the orthodox Stoic position is that mastery of all
three parts of philosophy is required for human flourishing. This is
apparent in the way the Stoics treat a number of philosophical
questions and in the many connections visible between the different
parts of their theory: conclusions in one part of Stoic philosophy
tend to reinforce and ratify those in another. For recent discussion
of the unity of the Stoic system, see Bronowski 2019, ch. 1; cf.
Christensen 1962, Ierodiakonou 1993, and Inwood 2012. For debates on
the connection of Stoic ethics to other parts of the system,
especially physics, see Annas 1993, who takes the ethical part to be
largely independent of physical theory, and Cooper 1999a and 2012, who
sees them as thoroughly intertwined (see also Betegh 2003).


### 1.3 Sources



It is impossible to consider the philosophical contributions of the
Stoics without noting a significant exegetical challenge: the paucity
of original texts. We do not possess a single complete work authored
by any of the first three heads of the Stoic school, Zeno, Cleanthes,
and Chrysippus, despite their prolific output in antiquity.
Chrysippus, for example, is reported to have written over 150 works,
of which only fragments remain. Likewise, the treatises authored in
the Middle Stoa are no longer extant. The only complete works by Stoic
philosophers that survive are those by writers of Imperial times,
Seneca, Epictetus, and Marcus Aurelius, as well as by lesser known
authors such as Cornutus, Cleomedes, and Hierocles (discussed in
Inwood 2022). Seneca, Epictetus, and Marcus focus to a significant
degree on ethics and only sparingly present the wide and extensive
theoretical bases of the system (for their views on logic, see Barnes
1997). These later Stoics also had philosophical agendas of their own,
so that their work might not always straightforwardly reflect the
views of their predecessors.



For detailed information about the Old Stoa, we have to depend on
either later doxographies, including Diogenes Laertius'
encyclopedia account in book 7 of his *Lives of Eminent
Philosophers*, pseudo-Plutarch's *Philosophers'
Opinions on Nature* (*Placita*), and Stobaeus'
*Excerpts* (*Eclogae*) - and their sources Aetius
(circa 1st c. CE) and Arius Didymus (1st c. BCE-CE) - or
other philosophers who discuss the Stoics for their own purposes.
Nearly all of the latter group are hostile witnesses. Among them are
the Aristotelian commentator
 Alexander of Aphrodisias
 (late 2nd c. CE) who criticizes the Stoics in *On Mixture* and
*On Fate* and contrasts their views piecemeal with those of
Aristotle in other works; the Platonist
 Plutarch
 (1st-2nd c. CE) who authored anti-Stoic tracts such as *On Stoic
Self-Contradictions* and *Against the Stoics on Common
Conceptions*; the medical writer
 Galen
 (2nd c. CE); the Pyrrhonian skeptic,
 Sextus Empiricus
 (2nd c. CE) who sharply criticizes most aspects of the Stoic system,
and in so doing provides detailed reports of Stoic doctrine; the
Neo-Platonist
 Plotinus
 (3rd c. CE); the Christian bishops Eusebius (3rd-4th c. CE),
Nemesius (circa 400 CE); and the sixth-century Neo-Platonist
commentator,
 Simplicius.
 Another important source is
 Cicero
 (1st c. BCE). Though his own philosophical position derives from that
of his teacher
 Philo of Larissa
 and the New Academy, Cicero is not without sympathy for what he sees
as the high moral tone of Stoicism. In his philosophical works -
especially *On Academic Skepticism*, *On the Nature of the
Gods*, and *On Moral Ends* (*De Finibus*) - he
provides summaries in Latin, with critical discussion, of Stoic views.
See also the entry on the
 Doxography of Ancient Philosophy.



From these sources, scholars have assembled collections of quotations
and doxographical reports. The first collection of its kind, von
Arnim's *Stoicorum Veterum Fragmenta* (SVF), gathered
fragments of Stoic works and testimonia in their original Greek and
Latin into a three-volume set in 1903-5. Fragments and
testimonia of the early Stoics are often referred to by von
Arnim's volume numbers and text numeration, e.g. SVF I.345. The
second half of the 20th century saw a revival of interest in
Hellenistic philosophy and in the Stoics in particular, not least
thanks to A. A. Long and D. Sedley's 1987 *The Hellenistic
Philosophers* (LS) which contains (in vol. 1) English translations
and commentary of many important texts on the Stoics, Epicureans, and
Skeptics. This was followed by *Hellenistic Philosophy* in
1988, a collection of primary texts edited by B. Inwood and L. P.
Gerson, with a second edition in 1997. In 1987, fragments pertaining
to dialectic were collected with a German translation in K.
Hulser's *Die Fragmente zur Dialektik der Stoiker*
(FDS). More recently, in 2022, *Later Stoicism 155 BCE to CE
200* by B. Inwood has made available the works of some often
neglected Stoic writers. 



The surviving evidence so gathered allows readers to piece together a
picture of the content and, in some cases, the development of Stoic
doctrine. In some areas, there is a fair bit of consensus about what
the Stoics thought, and we can even attach names to particular
innovations. However, in other areas the interpretation of our meager
evidence is hotly contested.


## 2. Physical Theory



Stoic physical theory included topics traditionally covered by natural
philosophy, and it is where the Stoics developed their ontology and
metaphysics. As is to be expected of their systematic approach to
philosophy, much of Stoic physics is fundamental in underpinning their
views in ethics and also interacts with some of their logic and
philosophy of language.


### 2.1 Bodies and Incorporeals



Stoic ontology is radically materialist or, more precisely,
corporealist. According to the Stoics, only bodies exist, because only
bodies have the capacity to act or be acted upon (Cicero, 45A; Sextus,
45B, Nemesius, 45C). This bold stance has wide-ranging implications:
the soul is a body, as are its attributes, so that wisdom, too, for
example, is a body (see below,
 2.9).
 This follows from the intricate make up of the world by principles
 (2.3).



Bodies nonetheless do not exhaust their ontology. Although only bodies
exist, i.e. only bodies have being, the Stoics allow for entities with
a lesser, or, at any rate, distinct, ontological status, that of
"subsisting" (*huphistanai*). This is the case of
the four incorporeals: time, place, void, and *lekta*. Of
these, void is perhaps the most intuitively grasped: it is
"incorporeal and intangible, neither has shape nor takes on
shape, neither is acted upon in any respect nor acts, but is simply
able to receive body" (Cleomedes, 49C). Void is essential to the
universe, not least because it surrounds it and allows for bodies to
move into it during the cyclical conflagrations (more on which below,
 2.5;
 on void, see de Harven 2015). Place's incorporeal status is
similarly justified insofar as it can be the receptor of body but
lacks the power to act or be acted upon. Understanding the incorporeal
status of time is trickier (for a recent treatment, see Salles 2018).
Some of what we might consider aspects of time are uncontroversially
bodies: day and night, or years, for example. We are also told that
the past and the future subsist, while the present
"obtains" or "is realized"
(*huparchein*, a term which has been the subject of much
scholarly attention: see Goldschmidt 1972, Barnes 2007, p. 69, Bailey
2014). One way of understanding the sense in which time is incorporeal
is by analogy with place, as the temporal intervals through which
bodies pass (cf. Sedley 1999, section 6). *Lekta*, the final
kind of incorporeal item, seem to stand out on this list. Usually
translated as "sayables" (from *legein*, "to
say"), they are roughly the sorts of things that can be said or
expressed by linguistic expressions and form the contents of
impressions and thoughts. They are treated in more detail in the
section on logic
 (3.2),
 but they also play a role in causation
 (2.8),
 and their metaphysical status has been the subject of much debate.
For a recent treatment of *lekta*, see Bronowski 2019; see also
Frede 1994b.



It is particularly interesting that the incorporeals are said to
"subsist" (*huphistanai*): the nature of this
ontological status remains a puzzle. What, if anything, they depend on
for their subsistence is not clear. It is usually agreed that place,
void, and time are mind independent, and many agree that this is also
the case of *lekta* (Long 1971 is perhaps the strongest
proponent of the alternative view that lekta are
mind-*dependent*). It is in any case generally clear that
incorporeals together with bodies are in some way essential to the
makeup of the universe, and that bodies and incorporeals share the
status of being "something" (*ti*).


### 2.2 Something: the Supreme Genus



"Something" (*ti*) is described as the
"supreme genus" (Seneca, 27A), broader than being, which
constitutes "the all" (*to pan*). The Stoics
recognize other entities to which they deny being, including fictional
entities and concepts or universals, which they place on a par with
each other as "figments of the mind" (Diogenes Laertius,
32C). Universals, in particular, are famously said to be
quasi-somethings (*hosanei ti*) or not-somethings
(*outina*) (Diogenes Laertius, 32C; Stobaeus, 30A). This has
led to much debate and speculation as to the status of these entities
and in particular where they stand relative to the class of
"somethings". For different views on the matter, see
Brunschwig 1988; Sedley 1984, 1999; Caston 1999; Sellars 2011; Bailey
2014. The metaphysical status of limits is similarly debated: see Ju
2009.


### 2.3 Principles and Mixture



Fundamental to Stoic physics and the explanations of natural phenomena
it offers are the two principles (*archai*), the active
principle and the passive principle, which bear complex and often
debated relations to *pneuma*, primary matter, the four
elements (air, water, fire, earth), and the cosmos as a whole. These
terms appear to be used in different senses in the surviving
fragmentary evidence, making the task of reconstructing a coherent and
unified physical theory somewhat challenging.



The active and passive principles together make up the world and
everything in it. To achieve this, the active principle, which is
identified with God or Zeus (see
 2.7
 for further discussion of Stoic theology), acts on the passive
principle, which is also called (at least by Zeno) primary matter.
Primary matter is eternal, unqualified, formless, and inert. Primary
matter is suffused throughout by the active principle in order to
create objects in the world. The active and the passive principles in
this way both constitute the cosmos and all objects in it. The Stoics
stressed that they are entirely blended, or mixed "through and
through" (Galen, 47H; Alexander of Aphrodisias, 48C), and
developed a theory of mixture which allowed for two bodies to be in
the same place at the same time (Hensley 2018; cf. Helle 2018 and
2022).



The vehicle for the divine active principle is called *pneuma*,
literally "breath" (Hensley 2020). *Pneuma*, by its
nature, has a simultaneous movement inward and outward which
constitutes its inherent "tensility". *Pneuma*
passes through all (other) bodies; in its outward motion it gives them
the qualities that they have, and in its inward motion makes them
unified objects (Nemesius, 47J; cf. Helle 2021). *Pneuma* comes
in gradations and endows the bodies which it pervades with different
qualities as a result. The *pneuma* which sustains an inanimate
object is a "tenor" (*hexis*, lit. "a
holding"). *Pneuma* in plants is, in addition,
"physique" (*phusis*, lit. "nature"),
and in animals, it is "soul" (*psuche*, see
 2.9
 below). 


### 2.4 Elements



The four elements, fire, air, water, and earth, are also important
entities to which the Stoics appeal in their physical theory. Sources
offer contradicting evidence as to the relationship of the elements to
other bodies and notably to the two principles. Unlike the passive
principle, elements appear to have some qualities (fire, for example,
is hot). Nonetheless, the elements also sometimes seem to constitute
or make up the principles themselves. The active principle, for
example, is said to be made up of fire and air, while matter is
sometimes said to be made up of water and earth (Nemesius, 47D). The
active principle is described as fiery (Galen, *On the Habits of
the Soul*, 4.783) and the tensility of *pneuma* is
sometimes accounted for by the interaction of hot fire and cold air
which rarefy and condense in turn, modifying the density of other
elements.


### 2.5 Cosmic Cycle and Conflagration



The elements, especially fire, play a central role in the cosmogony
and the cosmogonic process (Hensley 2021, Salles 2015, Long 2008, Hahm
1977). The Stoics hold that the cosmos goes through a cycle of endless
recurrence with periods of conflagration, a state in which all is
fire, and periods of cosmic order, with the world as we experience it
(Nemesius, 52C). In between these periods, the generation of the
elements occurs to create the cosmos in which all four elements exist.
(This apparently orthodox Stoic view was rejected by some, notably
Panaetius (Van Staaten, fr. 65).)



This idea of world-cycles punctuated by conflagrations raises a number
of questions. Will there be another you reading this encyclopedia
entry in the next world cycle? Or merely someone exactly similar to
you? Different sources attribute different answers to the Stoics on
these questions. (For sameness of person, see Alexander, 52F; for
someone indistinguishable, but somehow not identical, see Origen,
52G.) The doctrine of eternal recurrence also bears on the Stoic view
of time. Did they suppose that the moment in the next world cycle at
which you (or someone indistinguishable from you) reads this entry is
a moment in the future (so time is linear) or the very same moment
(with some notion of circular time)? The Stoic definition of time as
the "dimension (*diastema*) of motion" or
"of the world's motion" (Simplicius, 51A) hardly
seems to settle the question. For a clear exchange on the issue, see
Long 1985 and Hudson 1990; see also Greene 2018 and Salles 2018.


### 2.6 Categories



Aside from the basic ontology, the Stoics identify four genera of
being usually referred to as "categories" (see especially
Menn 1999): matter or substance (*hupokeimenon*), quality
(*poion*), disposition (*pos echon*), relative
disposition or relation (*pros ti pos echon*). Substance
is a portion of passive principles or elements. An object so conceived
just is a lump of matter (unlike prime matter, not entirely
undifferentiated insofar as it is a portion of it, distinct from some
other portion). Quality, which is subdivided into common and proper is
a portion of *pneuma*, organizing the matter so as to give it
certain properties. In particular, the portion of *pneuma*
serves to unify the underlying matter or substance so as to make it a
particular object. This latter role is likely to be that of what is
identified as a proper quality, for example the quality of being
Socrates (on proper qualities, see Nawar 2017). Proper qualities play
an important role in questions about identity and individuation (cf.
Sedley 1982, Lewis 1995). Objects do not exclusively belong to one or
the other category. We can speak of an object as the underlying
substance (the *hupokeimenon*) or of a qualified object capable
of bearing further qualities. Disposition and relations are
paradigmatically properties of already qualified objects, so that the
fist, for example, is said to be the hand disposed in a certain way
(Sextus, 33P). Relations are properties which depend on the relata, so
that a change in the relata causes the relation to cease to exist, for
example "being on the right of". The categories are put to
work in various ways, including in ethics and psychology (see
Alexander, 29A and Seneca, 29B), e.g. in the claim that knowledge is
the commanding faculty disposed in a certain way (Sextus, 33P).


### 2.7 God



In accord with their ontology, the Stoics make God a corporeal entity,
identical with the active principle. God is further characterized as
eternal reason (*logos*: Diogenes Laertius, 44B) or intelligent
designing fire or breath (*pneuma*) which structures matter in
accordance with its plan (Aetius, 46A). The Stoic God is thus immanent
throughout the cosmos and directs its development down to the smallest
detail. The entire cosmos is a living thing, and God stands to the
cosmos as an animal's life force stands to the animal's
body, enlivening, moving and directing it by its presence throughout.
The designing fire is likened to sperm or seed which contains the
first principles or directions of all the things which will
subsequently develop (Diogenes Laertius, 46B; Aristocles in Eusebius,
46G). This makes cosmic nature and all its parts inherently governed
by a rational force. God and divine actions are not, like the gods of
Greek Mythology, random and unpredictable. It is rather orderly,
rational, and providential. The association of God with
*pneuma* may have its origins in medical theories of the
Hellenistic period: see Baltzly 2003 and Annas 1992. On the issue of
God and its relation to the cosmos in Stoicism, see the essays in
Salles 2009.


### 2.8 Causes and Determinism



An important issue that straddles metaphysics and logic is that of
causal determinism. The Stoics are determinists about causation, who
regard the present as fully determined by past events, but who
nonetheless want to preserve scope for moral responsibility by
defending a version of compatibilism.



The Stoic analysis of causation is peculiar and might sound odd to the
modern ear. They say that every cause is a body which becomes the
cause to a body of something incorporeal. For instance, the scalpel, a
body, becomes the cause to the flesh, a body, of the incorporeal
predicate "being cut". (Sextus, 55B; cf. Stobaeus, 55A).
In addition, the Stoics develop a taxonomy of causes, the sources on
which are complex and not always clear, but which they brought to bear
in their defense of compatibilism.



What the Stoics call fate, which they identify with the working out of
the - rational and predictable - will of Zeus, is "a
certain natural everlasting ordering of the whole: one set of things
follows on and succeeds another, and the interconnexion in
inviolable" (Aulus Gellius, 55K). In other words, every event
that occurs in the world is the result of a cause or chain of causes,
so that everything that happens is metaphysically determined by
preceding causes in the chain (but not logically necessary; cf. de
Harven 2016). This sequence of causes is inescapable.



The inescapability of this sequence of causes leads to concerns about
action and moral responsibility. The first worry, which takes the form
of the so-called "lazy argument" (Cicero, 55S) is that, if
all my actions and their consequences are predetermined, there is no
point in acting at all: why call the doctor when ill, if it is
determined that the doctor will come? The second worry is that if my
actions come about by prior causes, they are not in my power and I am
therefore not truly responsible for them.



In response to the former challenge, Chrysippus claimed that not all
events are independent of one another. Rather, some are co-fated: part
of one and the same causal chain in such a way that they cannot be
dissociated. The call to the doctor and the doctor's coming are
so joined, as is the patient's healing. The doctor will not come
if she is not called, and the patient will not heal if the doctor does
not come. Calling the doctor is thus not superfluous or pointless. The
consequences of our actions may be predetermined, but only insofar as
they are caused by our actions. Our actions are thus not pointless: we
must act in order to ensure their consequences come about (see further
critical discussion in Brennan 2005, ch. 16).



In response to the concern about moral responsibility, Chrysippus
begins by distinguishing different types of causes. Although nothing
happens without an antecedent cause, he claims, not all antecedent
causes are sufficient for bringing about their effect (Plutarch, 55R):
some antecedent causes - those which are called "auxiliary
and proximate" (Cicero, 62C) - function as merely
necessary conditions.



Chrysippus deploys this distinction among antecedent causes in the
course of explaining how human actions are both causally determined
and subject to moral evaluation. Though the details are difficult, the
general strategy is clear enough and illuminated by the famous
cylinder and cone analogy:



> 
> 
> [Chrysippus] resorts to his cylinder and cone: these cannot begin to
> move without a push; but once that has happened, he holds that it is
> thereafter through their own nature that the cylinder rolls and the
> cone spins. 'Hence', he says, 'just as the person
> who pushed the cylinder gave it its beginning of motion but not its
> capacity for rolling, likewise, although the impression encountered
> will print and, as it were, emblazon its appearance on the mind,
> assent will be in our power.' (Cicero, 62C; see also Gellius,
> 62D)
> 
> 
> 



Consider two differently shaped solids - a cylinder and a cone
- both sitting atop the same steep slope. The two solids are
given a push of equal strength and begin to tumble down the hill. But
whereas the cylinder rolls in a straight path, the cone spins and
veers off to the side. Neither of these movements could have occurred
without the push, Chrysippus argues, but the particular way each solid
moves - whether it rolls or spins - is caused by its own
nature and "capacity for rolling". The push therefore
functions as an "auxiliary and proximate" antecedent
cause, which on its own is sufficient for causing the solid to move,
but not for causing it to roll rather than spin. Rather, it is the
individual nature of each solid that is so responsible. (Note that,
given the push the solid receives, together with its own nature and
capacity for rolling, each solid could not do otherwise than move in
the way that it does.)



Now consider two agents with different psychological profiles -
for instance, one person who is a glutton for sweets and another who
is not - both of whom are presented with a thick slice of carrot
cake. That the glutton rushes towards the cake and eagerly gobbles it
up, whereas the other agent does not (perhaps picking at it slowly
over a few hours), maps onto the cylinder's rolling and the
cone's spinning. Both agents receive the same external stimulus
for action and form "impressions" (mental representations,
*phantasiai* / *visa*) of the cake, but, like the push
in the case of the solids, these are not sufficient to cause the
differential behavioral response in the two agents. Rather, it is
their individual psychological profiles and the activity of giving or
withholding mental "assent" to the impression that eating
the cake is fitting to do which cause them to gobble the cake or not
(more on impression, assent, and action in
 2.9
 below). One's psychological profile is causally efficacious for
action, over and above the external stimulus. So among the antecedent
causes for human action - and by far the most decisive -
is the agent himself, his individual nature or psychological profile,
with the result that our actions are "up to us" or
"in our power" in a way that is relevant for the notion of
responsibility.



Much more could be said on this analogy. Detailed scholarly work on
the question of freedom and determinism in Stoicism can be found in
Bobzien 1998. See also Brennan 2005, ch. 14-15, Salles 2005, and
the entry on
 Ancient Theories of Freedom and Determinism.


### 2.9 Psychology



One further topic treated as part of Stoic physics is psychology, the
account of the soul. Here the Stoics argue that the soul is corporeal,
i.e. a body of a certain kind, since it is causally efficacious in a
way that only bodies are. If the soul were incorporeal, as some
ancient philosophers maintain, then it could not causally interact
with the body it animates, as it does e.g. in feeling pain when the
body suffers a flesh-wound or in causing the cheeks to blush when it
feels shame (Nemesius reporting Cleanthes, 45C). Furthermore, if
*x* and *y* come into contact with each other, then
*x* and *y* must be bodies. But the soul and the body it
animates are in constant contact, the Stoics hold, and are later
separated from each other at death (Nemesius reporting Chrysippus,
45D). Therefore the soul is corporeal.



What kind of body is the soul? As mentioned above
 (2.3),
 the Stoics identify the soul as *pneuma* at a certain degree
of tensility, more rarified than *pneuma* in the condition of
tenor (*hexis*), which is responsible for the coherence of
solid objects, and than *pneuma* in the condition of nature
(*phusis*), which regulates vital activities such as nutrition
and growth (Philo, 47P, Q). *Pneuma* in the condition of soul
enables the animal to take in perceptual information from its
surroundings, by forming impressions (*phantasiai*), and to
move itself from place to place, by forming impulses (*hormai*)
(Origen, 53A).



In a noteworthy break from both ordinary Greek usage and earlier
philosophical theories, the Stoics deny that all living things have
souls. Plants have tenor-*pneuma* and nature-*pneuma*
but not soul, since they do not engage in perception or
self-locomotion (Philo, 47P; Origen, 53A). Ensouled life is therefore
distinguished by the possession of the representational and
motivational faculties just mentioned: impression and impulse. In
narrowing the conception of the soul from a general principle of life
to one that refers specifically to these more obviously mental
characteristics, the Stoics take an important step forward in the
history of the philosophy of mind (on which see Annas 1992, Nawar
2020, and the entry on
 Ancient Theories of Soul).



Among ensouled creatures, some, such as mature human beings, possess
reason (*logos*) and are called "rational"
(*logikos*), while others, such as dogs or cows, do not and are
called "non-rational" (*alogos*). What can the
rational soul do that the non-rational cannot? Arguably, the most
important difference is the power of assent (*sunkatathesis*).
Assent is a faculty found only in the rational soul - in
particular, only in the ruling part or commanding faculty
(*hegemonikon*) of the rational soul (Aetius, 53H;
Iamblichus, 53K) - which enables us to adopt a critical stance
towards our own impressions and pass judgment on them (Origen, 53A).
Rational creatures give assent to the impression that *p* when
they deem *p* to be true; otherwise, they suspend assent on
*p*. ("Dissenting", or taking *p* to be
false, seems to be more precisely analyzed by the Stoics as suspending
assent on *p* and then giving assent to *not-p*.)
Rational creatures are morally and epistemically responsible for our
acts of assent, but not for the kinds of impressions we form: assent
is "in our power" or "up to us" in a way that
receiving an impression is not (cf. the cylinder and cone analogy
above,
 2.8).
 For the Stoics, there is no exaggeration in the claim that what kind
of person we are - whether we are virtuous or not, or
knowledgeable or not - depends entirely on our acts of assent.
The Stoic conception of assent is therefore of far-reaching
importance, both within their own system and for a proper
understanding of later philosophical debates (cataloged in Nawar 2020;
see also Frede 2011).



According to Stoic psychological theory,
 the outcome of giving assent to the impression that *p* will
be either a doxastic commitment of a certain kind (knowledge,
cognition, or the opinion that *p*; see
 3.7
 below) or a "rational impulse". Impulse, in general, is
the psychological event responsible for action, and in rational
creatures all impulses are "rational impulses" -
"movements of thought towards something in the sphere of
action" (Stobaeus, 53Q). Since assent is necessary and
sufficient for any rational impulse to be created, the Stoics can be
seen to endorse a strong form of "motivational
cognitivism": all cases of human action require, and follow
upon, the agent forming the judgment that the action in question is
appropriate for them to do (Klein 2015; Graver 2007; Inwood 1985).
This account would seem to rule out the possibility of occurrent
mental conflict, or *akrasia*, in the form of simultaneously
conflicting impulses, since it is impossible for the rational mind as
a whole to maintain, at one and the same time, conflicting judgments
(acts of assent) about what is fitting to do. (Some Stoics seem to
have re-analyzed cases of putatively simultaneous *akrasia* as
instead a rapid oscillation between opposing practical judgments:
Plutarch, 65G.) Stoic psychology and action theory can therefore be
understood as a rejection of the Platonic-Aristotelian approach of
positing non-rational sources of cognition and motivation in the
mature human soul, which can potentially oppose the dictates of
reason, in favor of a reversion to the monistic intellectualism of
Socrates. Like Socrates, the Stoics are committed to the claim that
human action invariably reflects the assessment of the rational mind
as a whole concerning what is appropriate to do in the scenario.



Given this theory, the Stoics construe the skeptical practice of
global suspension of judgment as entailing *apraxia*, i.e.
total inaction (cf. Plutarch, 69A). For further discussion of the
*apraxia* charge, see Obdrzalek 2012 and the entries on
 Arcesilaus
 and
 Ancient Skepticism.



According to the Stoics, human beings are not born with reason but
rather acquire it later in life (at age seven, according to Aetius,
39E). In childhood, then, we utilize a non-rational soul, just like
non-rational animals, and thus form impulses without the intervention
of assent. (On the development of rationality in humans, see Frede
1994c.) Interestingly, the Stoics also distinguish between rational
and non-rational *impressions*, i.e. the impressions formed by
rational and non-rational creatures (Diogenes Laertius, 39A). Exactly
how rational impressions (*phantasiai logikai*) differ from
their non-rational counterparts remains the subject of lively
scholarly debate. It is broadly agreed, however, that only rational
impressions are created under the direct influence of the
perceiver's concepts (*ennoiai*; cf. Galen, 53V), and
that only rational impressions express propositions
(*axiomata*, one kind of sayable or *lekton*) (see
Frede 1983, 1994c; Brittain 2002; Shogry 2019; for alternative views,
see Caston forthcoming, and Sorabji 1990).


## 3. Logic



The scope of the branch of philosophy the Stoics called
"logic" (*logike*) was wide, including not
only the analysis of argument forms and the development of a formal
system of logic, but also rhetoric, grammar, epistemology, and what we
might now call philosophy of language, including extensive theories of
language and meaning. Stoic contributions to logic and philosophy of
language, as well as the backdrop of Aristotelian and Megarian views
in the Hellenistic period, are thoroughly surveyed in Barnes, Bobzien
and Mignucci 1999, and in an abbreviated version by Bobzien in Inwood
2003.


### 3.1 Rhetoric and Dialectic



The branch of logic is subdivided into rhetoric and dialectic
(Diogenes Laertius, 31A). The former is described as "the
science [or knowledge, *episteme*] of speaking
well", though it also included, for example, extensive study of
etymology (for more on rhetoric, and in particular how narrow its
scope might have been, see Atherton 1988). Dialectic is "the
science [or knowledge, *episteme*] of what is true,
false, and neither" or "the science [or knowledge,
*episteme*] of what signifies and what is
signified" (Diogenes Laertius, 32C), mastery of which is
required for wisdom, since "the Sage is always a
dialectician" (Diogenes Laertius, 31C; the "Sage"
being the Stoic label for the ideal human being, i.e. the wise and
virtuous person). Dialectic as a field of study first sprung from the
practice of dialectic in the form of questions and answers but became,
largely under the influence of Chrysippus, increasingly systematized
and more technical to include the in-depth study of language, meaning,
arguments, and epistemology (cf. Gourinat 2000; Castagnoli 2010). It
is in fact in dialectic that we find most of the material that
influences the later so-called technical grammarians (on which see
more below,
 5.1,
 cf. Atherton and Blank 2003). This goes hand in hand with the
systematicity of Stoic philosophy. The Stoics believed language to be
inherently natural and to be such as to match the natural, rational
order of things, so that language has a natural propensity to capture
objects in the world and its structure. The study of language in
dialectic is thus an integral part of Stoic philosophy as a whole.


### 3.2 Philosophy of Language and *Lekta*



With the distinction of "what signifies" and "what
is signified", the Stoics introduce what is perhaps their most
celebrated innovation in the philosophy of language: the
*lekta* or "sayables". What signifies is uttered or
written language (words, sentences) in the form of air struck or
symbols in ink or in clay, and, as such, a body. What is signified, on
the other hand, is an incorporeal, namely a *lekton*. The term
itself is notoriously difficult to translate: from the verb
*legein*, "to speak" but also "to
reason", it is literally "what can be said" -
and not all *lekta* are in fact said. *Lekta* are
defined as "that which subsists in accordance with a rational
impression" (Sextus, 33B), and they form the contents of
rational impressions, concepts, and judgments.



The relationship of language to *lekta* is the subject of
debate, but it seems clear that *lekta* do not map neatly onto
the language that express them (Bobzien 2021). This is likely one of
the roots of the Stoic interest in ambiguity (on which see Atherton
1993). Nonetheless, the Stoics identified and classified different
parts of speech (proper noun, common noun, verb, conjunction, article,
to which some add *mesotes*, which is usually taken to be
the participle, though it could be adverbs: Diogenes Laertius 33A,
33M), each of which appear to express distinct signifieds. Verbs, for
example, typically express predicates
(*kategoremata*, 33M; see detailed discussion in
Bobzien and Shogry 2020). Whether all parts of speech express
*lekta* is unclear. Nouns, for example, may signify the elusive
cases (*ptoseis*), or qualities, or both (Diogenes
Laertius 33A, 33M, 34K; see Frede 1994a, Gaskin 1997, Bronowski 2019,
ch. 8-9).



The Stoics provide an extensive taxonomy of *lekta*. They begin
by dividing them into complete and incomplete. Incomplete
*lekta* include predicates, while complete *lekta*
appear to be those usually expressed by syntactically complete
sentences and include wishes, commands, questions, and the
all-important propositions (*axiomata*), which are
typically expressed by declarative sentences.


### 3.3 Propositions



Propositions are the only bearers of truth-value and the central
entity in much of Stoic philosophy of language and logic. Sometimes
also translated as "assertibles", Stoic propositions bear
some similarities to the modern proposition, but also some important
differences. Notably, Stoic propositions change truth-value over time,
so "it is day" is true while it is day, will become false
when it is night, and true again the following day, etc. The Stoics
also distinguish different types of propositions on the basis of their
subject (Sextus, 34E; Diogenes Laertius, 34K). The major
three types of simple affirmative propositions are the definite or
categorical, composed of a deictic or demonstrative and a predicate
("this one walks"); the middle or categoreutical, whose
subject is expressed by a noun ("Socrates walks",
"man sits"); and the indefinite whose subject is expressed
by an indefinite pronoun ("someone is sitting"). These
different types of propositions have different semantic but also
epistemological properties, as a result of the modes of references of
their subject (Durand 2019). For example, one perhaps surprising
property of the definite is that it can only be said of objects to
which one has successfully referred, so that, for example, the
proposition "this one is dead", can only be said of
something or someone that exists, but is "destroyed", that
is, is no longer a proposition and no longer has a truth-value if and
when the referent ceases to exist. As a result, "this one is
dead" can never be said truly, since it would be true only of
objects to which reference cannot be fixed deictically. This odd
feature is appealed to in the Stoic response to competing accounts of
modality
 (3.5).



The so-called simple propositions can be combined to form complex
propositions, composed of multiple simple propositions joined by a
connective. The Stoics thus developed accounts of the truth-conditions
of the conjunction ("*p* and *q*"),
disjunction ("*p* or *q*"), which they
treated as exclusive, and entered the lively ancient debate over the
correct understanding of conditionals ("if *p*, then
*q*"). (For more on this, see the entry on
 Ancient Logic, section 5.2.)
 They also treated the negation as truth-functional and as negating a
whole proposition ("it is not the case that *p*":
Alex. Aphr., *in Ar. An. Pr.* 402.12-19 = FDS 921), which
could be applied to simple or complex propositions. The Stoic interest
in non-simple propositions and their logical relations was shared
with, and built upon work by, philosophers in the
 Dialectical School.


### 3.4 Syllogistic



Arguments themselves are composed of complex propositions, including
at least two premises and one conclusion (Diogenes Laertius,
31A). This definition of arguments made the Stoic system one of
what we might now call propositional logic, by contrast with
Aristotle's logic of terms or predicate logic.



Syllogisms are arguments that take the form of one of the five
so-called "indemonstrables", which are axiomatic
arguments, or can be reduced to one by means of one of four rules of
inference, the *themata*. The five indemonstrables are familiar
argument forms presented in the following abbreviated way (Diogenes
Laertius, 36A, cf. Sextus, *M* 8.224-5, where
"the first" and "the second" are used in place
of *p* and *q*, following standard Stoic practice):


* if *p* then *q*; *p*; therefore *q*
(*modus ponens*);
* if *p* then *q*; not-*q*; therefore
not-*p* (*modus tollens*);
* not: both *p* and *q*; *p*; therefore
not-*q*;
* either *p* or *q*; *p*; therefore
not-*q*;
* either *p* or *q*; not-*p*; therefore
*q.*



A syllogism is a valid argument (Diogenes Laertius, 36A), as is any
argument whose conclusion follows from the premises, that is, in
Chrysippean terms, if the (Chrysippean) conditional formed from its
premises as antecedent and its conclusion as consequent is true
(Sextus, 72I; Diogenes Laertius, 36A). An argument is sound (literally
"true") if it is valid and its premises are true. For more
on the details on Stoic syllogistic, including a reconstruction of the
*themata*, see the entry on
 Ancient Logic sections 5.3-4
 and Bobzien 1996.


### 3.5 Modality



The Stoics also contributed to questions about modality, following in
the footsteps, indirectly, of
 Aristotle
 and, more directly, of the
 Megarians.
 At the heart of their interest were issues of possibility and
necessity tied in part to their commitment to causal determinism.



These matters primarily came to the fore in discussions of the
so-called
 Master Argument
 introduced by Diodorus Cronus. The Master Argument itself does not
survive and the details are the subject of debate (cf. e.g. Gaskin
1995, Denyer 1999). It involved the three apparently inconsistent
claims that (i) past truths are necessary, (ii) nothing impossible
follows from the possible, and (iii) there is something possible but
does not yet happen (Epictetus, 38A). Just why these claims are
incompatible is not entirely clear, though the Master Argument
reportedly worked to establish this result. In response, one had to
give up one of the claims. Which one of them one rejects has serious
implications for one's commitments with regards to the notions
of possibility and necessity. Diodorus Cronus rejected (iii), arguing
that what is possible is limited to what either is or will be true at
some point in the future (Boethius, 38C). Among the Stoics, Cleanthes
reportedly rejected (i), while Chrysippus rejected (ii). He argued
that the conditional "if Dion is dead, this one is dead"
is a counterexample, by appealing to the semantics of deictic
reference and reference failure (Alex. Aphr., 48F, cf. above
 3.3
 and Durand 2019). This arguably *ad hoc* argument enables
Chrysippus to retain both the necessity of the past and the thesis
that there are things which are possible but do not happen. This in
turn allows him to introduce a distinction between metaphysical
necessity (since all things are fated and pre-determined by antecedent
causes, see above
 2.8)
 and logical necessity (de Harven 2016) at the heart of his
compatibilist account. For more on Stoic views on modality, see
Bobzien 1986.


### 3.6 Paradoxes



The Stoics were interested in logical paradoxes and tackled a number
of them, including the Liar and the Sorites (Chrysippus, 37G; Cicero,
37H; Plutarch, 37I). The evidence on the solutions they offered is
poor but suggests a great deal of thought and sophistication. On the
Liar, see Cavini 1993 and Mignucci 1999. On the Sorites, see Bobzien
2002 and Vogt 2022. On the so-called Horned One, see Bobzien 2012.
(These logical paradoxes and the Stoic efforts to solve them should
not be confused with the "Stoic Paradoxes" discussed by
Cicero in his treatise of the same name; the latter refer to Stoic
doctrines in ethics running contrary to common opinion.)


### 3.7 Epistemology



The Stoics develop their epistemological theory as a sub-branch of
logic, but here, as in so many other cases, their conclusions lend
support to, and draw on, doctrines in other parts of their
philosophical system. Readers should familiarize themselves with the
 Stoic psychological theory
 presented above.



One central task of Stoic epistemology is to provide an account of
knowledge (*episteme*). Like Plato and Aristotle,
the Stoics conceive of knowledge as the paramount intellectual
achievement available to human beings and, accordingly, place
demanding conditions on its possession. Knowledge, for the Stoics, is
a maximally stable and modally robust grasp of reality, in the sense
that if *S* knows that *p*, then not only is *p*
true, but also *S* will not revise their commitment to
*p* in response to any degree of dialectical scrutiny that may
be applied to *S*. This requirement is registered in the Stoic
claim that knowledge is "secure and unchangeable by
reason" (Stobaeus, 41H) and seems originally born out of
reflection on the action of Plato's Socratic dialogues: whoever
asserts *p* but is led to accept *not-p* as a
result of elenctic cross-examination thereby reveals his own lack of
knowledge of *p* (even in cases where *p* happens to be
true) (Frede 1983).



Crucially, for the Stoics, the immutability characterizing
*S*'s knowledge that *p* does not rest on churlish
stubbornness in *S* or on their unquestioning faith in
*p*, but rather on *S*'s ability to understand
what makes *p* true and why the arguments against *p*,
if ever they are presented to *S*, are unsound. This thesis has
two significant consequences. First, to know *p* requires a
mastery of a comprehensive suite of dialectical skills, including
"irrefutability", i.e. "strength in argument, so as
not to be carried away into the contradictory" (Diogenes
Laertius, 31B), and a grasp of the canons of formal logic and Stoic
syllogistic, in order to distinguish valid from invalid arguments and
detect when the latter are offered in favor of *not-p*. Second,
knowledge is essentially systematic (Stobaeus, 41H). In knowing
*p*, *S* is in a position to appreciate how *p*
fits into a larger body of information, both within *p*'s
domain and in other parts of philosophical inquiry. Thus our Stoic
sources use "knowledge" to pick out both a stable
psychological condition and a token activity: the knowledge that
*p* (token activity) is only possible in a mind in which
*p* has been integrated and organized into a complex unified
structure (stable condition) (Vogt 2012, ch. 7; Brennan 2005, ch. 6).
For these reasons, the Stoics restrict knowledge to the Sage (Cicero,
41A; Sextus, 41C). Only the perfected human agent genuinely knows
anything, because only she possesses the wide-ranging argumentative
expertise necessary to defend what she has affirmed against any
possible challenge, together with a grasp of the further facts that
explain its truth.



Like virtue and happiness (see
 4.2
 below), knowledge does not come in degrees. One's endorsement
of *p* is either maximally stable and unable to be overturned
through rational means, or it is not, and virtue (as we will see) is
itself analyzed as knowledge of what is good, bad, and neither (cf.
Stobaeus, 61D, 61H). Since virtue is necessary and sufficient for
happiness (Diogenes Laertius, 61A), it follows that those lacking
knowledge will not be happy.



Given the fundamental importance of knowledge, how can it be acquired?
Attaining knowledge is exceedingly difficult, the Stoics concede
- not even the leaders of the school claimed to have it -
but, for all that, still humanly possible.



Here it is useful to consider the Stoics' three-fold distinction
between knowledge (*episteme*), cognition
(*katalepsis*), and ignorance (*agnoia*) (on which
Chrysippus wrote four books, now lost; Diogenes Laertius, 7.201).
Whereas knowledge is found only in the Sage, only the non-Sage is
afflicted by ignorance (Stobaeus, 41G). Knowledge and ignorance are
thus mutually exclusive conditions. This result also falls out of the
Stoic definition of ignorance, as "changeable and weak
assent" (Stobaeus, 41G). The Stoics therefore divide human
agents into two sharply disjoint categories, the knowledgeable and the
ignorant, with the overwhelming majority of us falling into the latter
camp. To account for the move from a condition of ignorance to a
condition of knowledge, Zeno introduces a mental state he calls
*katalepsis* (translated by Long and Sedley as
"cognition" but elsewhere as "grasp" or
"apprehension"; in non-technical contexts the Greek word
connotes an act of seizing something with the hands).



The basic idea behind Zeno's proposal is that, when *S*
cognizes (= has *katalepsis* of) *p*, *S*
successfully latches on to or grabs hold of a truth, because the
relationship between *S* and *p* ensures that *p*
cannot be false: roughly, the process through which *p* enters
*S*'s mind and the clarity and distinctness with which
*p* is represented are such as to guarantee *p*'s
truth. Cognition is therefore factive - there is no cognition of
falsehoods - but not all true judgments amount to cognition, as
when, for instance, one assents to *p* in a state of
hallucination or intoxication but *p* happens to be true
(Sextus, 40E). Cognition, then, is a mental state characterized in the
first instance by its representational fidelity to the external world
and not - as with knowledge and ignorance - by the
disposition of the agent to retain or revise it under varying
dialectical circumstances. In this sense, cognition is "placed
between" knowledge and ignorance (Cicero, 41B): it is an
intellectual achievement shared by both Sages and non-Sages (Sextus,
41C). This entails, however, that any token cognition that *p*
will count as either knowledge or ignorance, depending on the
character of the cognizer. The Sage's cognition that *p*
is a piece of knowledge, since it is immutable and systematically
organized in the manner described above, while the non-Sage's is
a piece of ignorance (Cicero, 41B), since it is still insecure and
prone to be abandoned in the face of contrary argumentative pressure
(Plutarch, 31P; see Shogry 2022). This led the Academic skeptic
Arcesilaus to object that cognition will be an empty category and have
no independent existence apart from knowledge and ignorance (cf.
Sextus, 41C). But the Stoics have good reasons for presenting their
tripartite distinction as they do, because they see cognition as the
"natural foundation" (or "starting point":
*principium*) for knowledge (Cicero, 41B).



Beginning with Zeno, the Stoics characterize cognition
(*katalepsis*) as an assent to a special kind of
impression, one that functions as a criterion of truth and thus
guarantees its own veridicality: such an impression they call
"cognitive" (lit. "cognition-prompting",
*kataleptikos*) (Sextus, 41C; see also *PH* 3.241
and *M* 8.397). While some scholars simply transliterate this
label as "kataleptic", Long and Sedley's translation
of "cognitive", whatever its infelicities, helpfully
replicates the connection, visible in the Greek, with the outcome of
assenting to such an impression: "cognition". (Similarly,
when *katalepsis* is translated as "grasp" or
"apprehension", we find "graspable" or
"apprehensive" for *kataleptikos*; Cicero
translates the two terms into Latin as *comprehensio* and
*comprehendibile*, respectively.) So cognition is guaranteed to
be true because it is analyzed as an assent to an impression that is
itself guaranteed to be true: cognitive impressions "have a
peculiar power of revealing their objects" (Cicero, 40B).



The existence of cognitive impressions makes cognition possible, and
knowledge, the Stoics hold, is attained when all of one's acts
of assent amount to cognition: the Sage is distinguished from the
non-Sage in assenting exclusively to cognitive impressions.
"Assent iff cognitive" therefore functions as a norm of
Stoic epistemology and sketches a pathway to progress from ignorance
to knowledge. The Stoics assume that cognition, especially of
perceptual facts, is commonplace and regularly achieved by the
non-Sage, and so that on these occasions there is no great obstacle to
obeying the norm. For instance, ordinary agents regularly entertain
and accept the cognitive impression that "it is day" when
standing in a sunny field at noon. But other cases present greater
challenges, such that the non-Sage will assent to an impression that
fails to be cognitive and thus infect their mind with
"opinion" (*doxa*) (Plutarch, 41E). By contrast,
the Sage is entirely free of opinion, since she withholds assent on
any impression that is non-cognitive (Stobaeus, 41G). (Scholars
dispute the status of opinion in Stoic epistemology, but on one
well-attested usage *doxa* is the label used specifically for
the non-Sage's acts of assent to non-cognitive impressions; for
an alternative view, on which opinion is identical to ignorance, see
Meinwald 2005 and Vogt 2012, ch. 7.)



Unsurprisingly, then, the Stoics expend no small effort explaining
what distinguishes cognitive and non-cognitive impressions. Zeno
eventually settled on the following three-clause definition of the
cognitive impression, which was retained throughout the history of the
school. According to the Stoics, "a cognitive impression is one
which:


1. arises from what is, and
2. is stamped and impressed exactly in accordance with what is,
3. of such a kind as could not arise from what is not."
(Sextus, 40E)



These three clauses are construed by the Stoics as providing
individually-necessary and jointly-sufficient conditions for an
impression to be cognitive (Nawar 2014). Together, they are supposed
to capture the feature(s) shared by all and only cognitive
impressions, in virtue of which they serve as criteria of truth
(Diogenes Laertius, 40A). However, their precise interpretation
remains highly controversial.



One longstanding dispute concerns the meaning of "what is"
as it features in clause (1): is it to be understood
*existentially* or *veridically*? On the existential
interpretation, "what is" refers to a being or real
object, so that clause (1) requires the cognitive impression to be
caused by ("arise from") an existing object in the
external world. So construed, clause (1) rules out cases where an
impression is formed solely through the activity of the mind (e.g. in
a hallucinatory episode). However, this reading has been challenged on
both textual and philosophical grounds. Textually, the Greek phrase
translated by Long and Sedley as "what is" does not use a
form of "to be" (*einai*) but rather a different,
technical expression: "to obtain" (*huparchein*).
According to Stoic metaphysics (see above,
 2.1),
 only bodies "are" or "exist"
(*einai*), and so if clause (1) were intended to refer
specifically to external objects (bodies), we would expect a form of
*einai*, not *huparchein*. Philosophically, the
existential reading implies there are only cognitive impressions of
bodies. However, the Stoics acknowledge the possibility of cognition
concerning incorporeal propositions, for instance, truths about the
nature of the gods (Diogenes Laertius, 40P), and insofar as cognition
consists in an assent to a cognitive impression, there should be
cognitive impressions of these true incorporeal propositions as well.
(On this issue, see Schwab forthcoming, and the recent exchange
between Vogt 2022 and Nawar 2022.) The veridical interpretation points
to a resolution of both these difficulties. On this reading,
"what is" picks out a true proposition, in line with the
Stoic claim that true propositions "obtain" rather than
"exist" (cf. Sextus, 34D) and with further evidence in
Cicero (cf. 40I and *Acad*. 2.112). Thus clause (1) amounts to
a veridicality requirement: all cognitive impressions must be true.
Moreover, a veridical reading of clause (1) would also seem to allow
for the possibility that there are cognitive impressions of true
propositions, though this point is controversial: see Sedley 2002 and
Nawar 2014. For an effort to rehabilitate a version of the existential
reading, see Stojanovic 2019 and Caston forthcoming.



The major debate over clause (2) turns on whether it serves to
characterize the cognitive impression's phenomenological
character, causal history, or both, and one's stance on this
question affects one's interpretation of clause (3) in turn.
Both Cicero and Sextus report that clause (3) was added by Zeno to an
earlier definition consisting just of clauses (1) and (2) (40D, E),
and the grammar of clause (3) itself suggests it should be read as a
further elucidation of clause (2). According to what has come to be
called the "internalist" interpretation, clause (2)
requires that the cognitive impression display a unique level of
clarity and phenomenological sharpness, which is lacking in any false
impression (clause (3)) (Sedley 2002). By contrast, on the
"externalist" reading, clause (2) stipulates that the
cognitive impression is appropriately caused, i.e. "exactly in
accordance with" the fact it represents and not any other,
without speaking to its phenomenological qualities: the causal link
between the cognitive impression and its object is "of such a
kind as" no false impression will possess (clause (3)) (Frede
1983; for the viability of this interpretation, see the exchange
between Perin 2005 and Shogry 2018). A "hybrid" view reads
clauses (2) and (3) as stating that the cognitive impression enjoys
maximal phenomenological clarity *because* it is caused in the
appropriate way, i.e. by the state-of-affairs it represents and no
other (Nawar 2014; cf. Frede 1999).



From its initial formulation by Zeno, the Stoic account of the
cognitive impression was fiercely contested by the school's
skeptical opponents, provoking a centuries-long debate over its
tenability (Annas 1990). Academic skeptics, such as Arcesilaus and
Carneades, argued that no impression could meet all three clauses of
Zeno's definition (40 H, J), with the result that cognition, as
the Stoics conceive of it, is impossible, since cognitive impressions
do not exist. For discussion of these Academic arguments, see the
entries on
 Ancient Skepticism,
 Arcesilaus,
 Carneades,
 and
 Philo of Larissa.
 Sextus Empiricus presents a number of further arguments devised by
Pyrrhonian skeptics to show that cognitive impressions cannot serve as
criteria of truth.



For helpful comments on the relation in Stoicism between reasonable
impressions and cognitive impressions, see Brennan 1996 (with Diogenes
Laertius, 40F). For articles exploring the influence of Plato's
*Theaetetus* on the development of the Stoic account of the
cognitive impression, see Shogry 2021 and Long 2002.


## 4. Ethics



Stoic ethics is eudaimonist in structure, in the sense that it posits
happiness (*eudaimonia*) - a well-lived, flourishing life
- as the rational agent's ultimate practical goal or end
(*telos*). Thus the Stoics characterize happiness as "the
end, for the sake of which everything is done, but which is not itself
done for the sake of anything" else (Stobaeus, 63A). This core
eudaimonist thesis is shared by the Epicureans, Peripatetics, and
other philosophical schools contemporary with the Stoics, and is
regarded as an uncontroversial starting-point for further ethical
reflection and theorizing (Annas 1993). Every human agent, it is
assumed, wants nothing more than to live a flourishing, happy life and
therefore arranges their own projects and efforts according to what
they think will accomplish this goal. Unfortunately, however, most
human beings are mistaken about what will in fact make them happy.
Regardless of what they themselves might say about the value and
success of their lives, most humans, according to the Stoics, hold
false opinions about what their happiness consists in, i.e. false
opinions about what is good. In the eudaimonist framework in which
Stoic ethics is articulated, to claim that *x* is good (or a
good) is to claim that *x* is a constituent or causal source of
happiness. Stoic ethical theory therefore aims to provide an account
of what *really* is good and what *really* brings
happiness to a human being, so that we can guide our lives
accordingly. In this respect, the Stoics' aims are continuous
with those of the Epicureans, Peripatetics, and other rival ethical
schools, but the eudaimonist philosophers of the Hellenistic and Roman
periods put forward different accounts of what human happiness
genuinely consists in, so that it became standard practice among
ancient writers to distinguish each school by its view of "the
highest good" (*summum bonum*) and "the end"
(*telos* / *finis*) (cf. the title of Cicero's
treatise, *De Finibus*).


### 4.1 The Telos



What, then, is the Stoic account of the end? How do they describe the
kind of activity in which human happiness consists?



> 
> 
> Zeno represented the end as: 'living in agreement'. This
> is living in accordance with one concordant reason, since those who
> live in conflict are unhappy... Cleanthes, [Zeno's] first
> successor, added 'with nature', and represented it as
> follows: 'the end is living in agreement with nature'.
> (Stobaeus, 63B)
> 
> 
> 



Although our Stoic sources record a number of further descriptions of
the *telos*, some of which we will consider below, the
formulation attributed in this passage to Cleanthes (and elsewhere to
Zeno himself, see Diogenes Laertius 63C) - "living in
agreement with nature" - offers a convenient entry-point
into the Stoic ethical system.



One feature of the happy life brought out by Zeno's shorter
formulation - "living in agreement" - is
agreement *with oneself*. The flourishing human being is free
of both internal psychological division and vacillation in her
practical commitments and priorities, such that she enjoys "a
good flow of life" (Stobaeus, 63A). In characterizing the
flourishing life as one which adheres to "one concordant
reason" (Stobaeus, 63B), i.e. one coherent practical outlook
that is never at odds with itself or discordant over time, Zeno
respects what is arguably a basic intuition about human happiness
(Cooper 2012; cf. Aristotle, *Nic. Eth.* 1.4,
1095a22-26).



With the longer formulation, the Stoics underscore their commitment to
a bolder thesis, that, in living with agreement with herself, the
happy agent is also living in agreement with nature and so with the
cosmos as a whole:



> 
> 
> Therefore, living in agreement with nature comes to be the end, which
> is in accordance with the nature of oneself and that of the whole,
> engaging in no activity wont to be forbidden by the universal law,
> which is the right reason pervading everything and identical to Zeus,
> who is this director of the administration of existing things.
> (Diogenes Laertius, 63C)
> 
> 
> 



As we saw above
 (2.7)
 in the context of Stoic physics - i.e. the study of nature
- God or Zeus is identified with the active principle of the
universe, the corporeal mind present everywhere within it, structuring
and shaping the underlying matter according to an all-encompassing,
perfectly rational plan. For a human being to live "in
agreement" (*homologoumenos*) with cosmic nature
therefore requires attuning her own reason (*logos*) with that
of the whole, by thinking the same thoughts about her situation and
circumstances as does Zeus in governing the portion of the world she
occupies (Cooper 2012). In this way, the flourishing agent lives in
conformity "with the will of the administrator as the
whole" (Diogenes Laertius, 63C).


### 4.2 Virtue



To bring our mind into this state of agreement and achieve the
*telos*, the Stoics argue that only one thing is needed:
virtue. Virtue is the perfected condition of human reason (Seneca,
63D), or "a soul which has been fashioned to achieve consistency
[or agreement, *homologia*] in the whole of life"
(Diogenes Laertius, 61A). Having developed her own power of reason to
its fullest extent, the virtuous agent not only lives a life that is
the highest expression of human nature - the best possible
condition for a human being to be in, given the kind of creature we
are - but also replicates in herself the condition of the divine
(Seneca, 60H; Plutarch, 61J). To live virtuously is therefore to live
in agreement with both human nature and cosmic or divine nature at
once (Chrysippus in Diogenes Laertius, 63C).



Since virtue is the perfection of human rationality, and knowledge is
the highest rational achievement open to us, it is unsurprising that
the Stoics identify the virtues as forms of knowledge. The virtue of
courage, for instance, just is knowledge of what should be endured and
feared, and the Stoics argue that this virtue is inseparable from all
the rest: whoever has one virtue has them all (61B-H; see Schofield
1984). Thus the knowledge that constitutes courage entails a
systematic grasp of further topics in ethics (e.g. of what should be
done and what is choiceworthy, the provinces of prudence and
moderation, respectively) and also, remarkably, of the truths of logic
and physics as well (Cooper 1999a, Menn 1995; for an alternative view,
see Annas 1993). One cannot genuinely know (e.g.) what should be
endured or feared without also knowing how knowledge itself is
acquired (a topic in logic) and how nature operates in both human
beings and the cosmos at large (a topic in physics). The knowledge
that makes up virtue therefore ranges beyond the narrowly ethical, and
since knowledge is an all-or-nothing affair, so too is virtue
(Plutarch, 61T). For the Stoics, comprehensive knowledge of reality
(including but not limited to moral facts) is what is necessary and
sufficient to live in agreement with nature and be happy.


### 4.3 Indifferents



This sketch of Stoic eudaimonism allows us to better appreciate two of
their most contentious ethical doctrines: (1) human happiness is fully
in our power and (2) virtue is the only good.



Recall that, for the Stoics, the possession of knowledge depends
solely on the agent's acts of assent, and all acts of assent are
in the agent's power (see above,
 2.8
 and
 2.9).
 So if virtue is knowledge and both necessary and sufficient for
happiness, it follows that happiness will also be in the agent's
power and entirely up to them.



Let us grant for the sake of argument that virtue and knowledge are in
the agent's power. Even so, one might object that it is
impossible to be happy in the midst of grave misfortune and material
deprivation: a terminally ill patient racked with pain, impoverished
from medical bills, and reviled by all of society cannot be happy,
even if he is virtuous. This intuitive thought led Academic and
Peripatetic philosophers working in the eudaimonist tradition to argue
that, while virtue is necessary for happiness, it is not sufficient,
or to recognize different degrees of happiness and hold that, while
virtue is necessary and sufficient for a minimal amount of happiness,
it does not suffice for full or maximal happiness (cf. Cicero, *De
Finibus* 5.77; Seneca, *Moral Letters* 85.18-23). On these
views, some things other than virtue and lying outside the
agent's power - i.e. his share of "external
goods" - will make a difference to his happiness.



The Stoics reject such approaches:



> 
> 
> They [the Stoics] say that some existing things are good, others are
> bad, and others are neither of these. The virtues - prudence,
> justice, courage, moderation and the rest - are good. The
> opposites of these - foolishness, injustice and the rest -
> are bad. Everything which neither does benefit nor harms is neither of
> these: for instance, life, health, pleasure, beauty, strength, wealth,
> reputation, noble birth, and their opposites, death, disease, pain,
> ugliness, weakness, poverty, low repute, ignoble birth and the like.
> For just as heating, not chilling is the peculiar characteristic of
> what is hot, so too benefiting, not harming is the peculiar
> characteristic of what is good. But wealth and health no more do
> benefit than they harm. Therefore wealth and health are not something
> good. (Diogenes Laertius, 58A)
> 
> 
> 



In sharp contrast with eudaimonist theories which regard health,
wealth, reputation, etc. as "external goods", the Stoics
maintain that such items are neither good nor bad and, thus,
"indifferent" (*adiaphora* /
*indifferentia*) to human happiness. To establish this
conclusion, the Stoics do not rely on the claim that wealth, for
instance, *sometimes* benefits and *sometimes* harms the
agent. Instead, the Stoic position is that wealth "neither does
benefit nor harms": in no case is a human life ever made better
or worse by the possession or deprivation of wealth (or health or
reputation etc.). Just as what is hot necessarily provides heat, so
too what is good necessarily provides benefit (cf. Sextus, 60G). The
Stoics' fundamental axiological thesis, then, is that only
virtue benefits a human being and makes our lives go well, so only
virtue is good.



The Greek Stoics were prolific in crafting arguments in support of
this thesis, a number of which survive in our sources (e.g. Cicero,
60N; see also Seneca, *Moral Letters* 82, 85, and 87). Among
other strategies, Chrysippus appealed to his account of human nature
to show that only virtue is good, arguing that human nature is such
that only the perfection of reason is genuinely beneficial to us (cf.
Cicero, 64K and Brennan 2009; see also Klein 2016). In any event, the
Stoics fully embrace the conclusion that Aristotle considers too big a
bullet to bite (cf. *Nic. Eth.* 1.5, 1095b33-1096a2):
they maintain that, even while being tortured on the rack, his body
mutilated and searing with pain, and isolated from all his family and
friends, the virtuous person is maximally happy (Cicero, *De
Finibus* 3.42). Indeed, according to the Stoics, he is equally
happy as he was before the torture began, since at both times he
possesses the one thing that is really beneficial - virtue
- despite having a different share of indifferents (physical
pain, health, etc.). Human happiness therefore does not come in
degrees, on the Stoic view. Provided that the agent is virtuous (and
regardless of *how long* she continues to possess virtue:
Cicero, *De Finibus* 3.45-7), nothing external will
detract from or add to her personal flourishing.



With respect to their contribution to happiness, then, all
indifferents are on a par (Diogenes Laertius, 58B). From this bracing
thesis, one might be tempted to infer that there is no reason to exert
oneself in the pursuit of one type of indifferent (e.g. health) over
its opposite (e.g. disease). While some marginal figures in
Zeno's circle endorsed this kind of absolute equality of
indifferents, such a position was explicitly rejected by Chrysippus,
and it did not become Stoic orthodoxy (Cicero, 58I; cf. Sextus, 58F).
Instead, the mainstream Stoic view is that some indifferents -
such as health, wealth, and reputation - are of a promoted or
preferred type (*proegmena* / *praeposita*), have
value (*axia* / *aestimatio*), and are according to
nature (*kata phusin* / *secundum naturam*), such that
is appropriate or dutiful or one's proper function
(*kathekon* / *officium*) to select them over
their opposites in normal circumstances (Cicero, 59D; Stobaeus 58C-E).
For this reason, the virtuous agent will typically pursue (e.g.)
health and undertake the further steps needed to obtain it (e.g. eat
salad, exercise, etc.), even though her successful acquisition of
health - her actually being healthy rather than unhealthy
- makes no difference to her happiness and is neither good nor
bad. The virtuous agent is therefore not lackadaisical in her attitude
toward indifferents, according to the orthodox Stoic account, but
rather energetic and conscientious in her pursuit of those which are
preferred, valuable, and according to nature: her general policy will
be to select these and reject their opposites.



The Stoics' ancient critics replied that this doctrine was
incoherent, even confused, and it is indeed difficult to see how
something could be both indifferent to our happiness and nevertheless
rational to care about and pursue. The ancient critique of the Stoic
account of indifferents can be formulated as a dilemma (cf. Plutarch,
64C; Cicero, 64F, L; see Klein 2015, Barney 2003). According to these
critics, there are just two ways the Stoics can explain why we should
pursue health, wealth, and other preferred indifferents, both of which
leading to self-contradiction: either (i) these items really are good
and directly or indirectly contribute to human happiness, or (ii)
happiness is not the ultimate practical goal. Option (i) makes the
pursuit of these items intelligible, on the grounds that possessing
them is good for human beings and happiness-affecting, but is
inconsistent with the Stoic claim that only virtue is good. On this
option, "preferred indifferents" turn out to be external
goods by another name. Option (ii) respects the Stoic insistence that
these items are genuinely indifferent to our happiness, but sacrifices
the bedrock eudaimonist thesis that happiness is "the end, for
the sake of which everything is done" (Stobaeus, 63A). On option
(ii), indifferents are pursued for the sake of a goal independent
from, and standing outside of, the agent's own happiness, but
this result is one that no eudaimonist school can consistently
accept.



Whether the Stoic account is ultimately impaled on these two horns
remains the subject of ongoing scholarly debate. However, the
epistemic interpretation of Stoic indifferents - first sketched
by Cooper 1999a and Brennan 2005 but authoritatively presented in
Klein 2015 - deserves further consideration here, as a promising
attempt to rescue the Stoics from the dilemma. On this interpretation,
the agent is justified in selecting (e.g.) health over its contrary
indifferent, illness, not because health is itself good or because
there is some happiness-independent reason to be healthy as opposed to
sick, but instead because, for finite agents like us, who lack
knowledge of future events, selecting promoted indifferents over their
opposites is generally the most epistemically responsible way of
following the will of Zeus (cf. Chrysippus in Epictetus, 58J).



Recall that the *telos* is standardly specified as
"living in agreement with nature". Chrysippus holds that
this formulation is equivalent to "living in accordance with
experience of what happens by nature" (Diogenes Laertius, 63C).
According to Diogenes of Babylon, the *telos* can also be
described as "reasoning well in the selection and dis-selection
of things in accordance with nature" (Stobaeus, 58K).
Diogenes' formulation suggests that the correct
*selection* of indifferents makes a positive contribution to
human happiness, even though their *possession* does not.
Moreover, the Stoics think that a selection can be correct even if
Zeus decides not to produce the indifferent that the agent pursues:
like excellent dancing, virtuous selection of indifferents does not
require the acquisition of any object external to the agent in order
to count as successful (Cicero, 64H). So, on the epistemic
interpretation, when the virtuous agent selects health over illness,
she does not act for the sake of obtaining health, as if being healthy
rather than sick would make a difference to her flourishing, but
instead because pursuing health on this occasion reflects her
"experience of what happens by nature" and follows upon
her best assessment of what conformity to Zeus' providential
cosmic plan requires of her in this instance. (See Stobaeus 65Q, with
discussion in Inwood 1985, ch. 5, and Brennan 2000, for the
"reservations" included in the Sage's selections of
indifferents.)


### 4.4 Deliberation



So far, for ease of exposition, we have focused on a simplified case
in which an agent deliberates over whether to select one preferred
indifferent over its opposite. But for the Stoics the typical case of
deliberation is much more complicated, with more than one agent and
more than one kind of indifferent at stake, so that it may not be
immediately obvious what the appropriate action or proper function is
in a given scenario. However, since failing to perform one's
proper function is incompatible with living in agreement with nature
(Stobaeus, 59I; Diogenes Laertius, 59J), it is incumbent upon the
Stoic theorist to assist ordinary agents and moral progressors in
their deliberation in these cases. To this end, the Greek Stoics
composed works *On Proper Functions* (*Peri
Kathekonton*), with Panaetius' forming the basis
of Cicero's treatise of the same name (*De Officiis*).
The main assumption guiding these Stoic works is that indifferents
serve as the subject-matter or raw material of virtue (Plutarch, 59A):
the virtuous agent must impartially weigh indifferent against
indifferent when deliberating over what to do. For the Stoics, justice
requires distributing the right amount of indifferents to each person
(cf. Plutarch, 61C and Stobaeus, 61H), and in some cases the just
agent will select a dispreferred indifferent for herself, in order to
allocate a greater amount of preferred indifferents to others. Since
being alive is itself a preferred indifferent, there are cases when
one's proper function is to sacrifice one's own life (e.g.
to save others fleeing the battlefield or to avoid large amounts of
future pain and disease) (Cicero, 66G; Diogenes Laertius, 66H).
Although it might be tempting to attribute to the Stoics a simple
maximization rule, on which one's proper function just is to
maximize the net amount of preferred indifferents for the most agents,
our evidence points against the idea that the Stoics accepted any one
single principle for determining what one's proper function is
in a given scenario (see Brennan 2005, chs. 11-13, and the
exchange between Inwood 1999 and Striker 1987; for defeasible
guidelines or rules of thumb that may assist the ordinary agent in
finding what is appropriate, see e.g. Seneca, *Moral Letters*
94 and 95).


### 4.5 Stoic Cosmopolitanism



How far do the demands of justice extend? To *all*
human-beings, the Stoics insist (Plutarch, 67A; Cicero, 57F;
Hierocles, 57G; Anonymous Commentary, 57H). In virtue of our shared
rationality, all human beings, together with Zeus, make up the
citizenry of one universal city or cosmopolis (Marcus Aurelius, 4.4;
Arius Didymus, 67L). The just agent therefore looks beyond her
immediate physical proximity and conventional political community when
distributing indifferents and takes the interests of every human being
- even the "most distant Mysian" (Anonymous
Commentary, 57H) - into account.



One motivation for characterizing the cosmos as a kind of city is
Stoic thinking on law, which in turn draws on wider tenets of their
physical and ethical theory. According to the Stoics, to live in
agreement with nature and achieve the human *telos* involves
"engaging in no activity wont to be forbidden by the universal
law (*ho nomos ho koinos*), which is the right reason pervading
everything and identical to Zeus" (Diogenes Laertius, 63C; cited
above,
 4.1).
 The providential activity of Zeus in administering the cosmos thus
serves as *universal law*, setting a perfectly
rational standard for human beings to follow and emulate (Marcian,
67R). So, since "a city is a group of people living in the same
place and administered by law" (Dio Chrysostom, 67J), and all
human beings are bound by the universal law of Zeus - a law that
is "diffused over everyone, consistent, everlasting"
(Cicero, 67S) - it follows that the cosmos is a kind of a
city.



For further details of Stoic cosmopolitanism, see Vogt 2008, Schofield
1991, and the entries on
 Ancient Political Philosophy
 and
 Cosmopolitanism.


### 4.6 Oikeiosis



To support their account of cosmopolitan justice and their fundamental
axiological thesis that only virtue is good, the Stoics rely on their
doctrine of *oikeiosis* ("appropriation" or
"affiliation"; the Greek term suggests a process whereby
objects come to be recognized as *oikeion* - as
"appropriate" or "affiliated" or
"belonging" to the creature in question). This doctrine
begins with the observation that, straight from birth, every creature
seeks to preserve its own constitution, even when this is painful
(Diogenes Laertius, 57A; Seneca, 57B): its own constitution is thus
the first thing each creature sees as *oikeion* to it and,
hence, as an object of concern. This is because each animal is born
with a capacity for self-perception, which enables it to detect, among
other things, what is appropriate or harmful to its constitution, and
a capacity for impulse, which enables it to pursue or avoid objects
accordingly (Hierocles, 57C). So, to use Seneca's example, a
turtle that has fallen on its back perceives that this situation is
unfavorable to its constitution and forms an impulse to right itself.
Moreover, the turtle does all this by nature, without having been
trained to do so, showing that non-rational creatures are set-up by
providential nature to perceive what is needed for their own
teleological success and to act appropriately in pursuit of this goal.
Newborn infants and children are no exception: as we saw above
 (2.9),
 humans are not born with reason but rather acquire it later in life,
so that prior to maturing into adults we employ a non-rational soul
and pursue the objects appropriate for a constitution of this kind.
The transition into adulthood comes when "reason supervenes as
the craftsman of impulse" (Diogenes Laertius, 57A), i.e., when
we acquire a rational nature and begin to form "rational
impulses" (Stobaeus, 53Q). The Stoics maintain that the rational
constitution of a mature adult differs from that of a non-rational
child (Seneca, 57B), and so too the things favorable to it.
Furthermore, adding a social dimension to the theory of
*oikeiosis*, the Stoics observe that humans, like members
of certain animal species (bees, ants, etc.), naturally cooperate with
one another, and, in general, "it could not be consistent for
nature both to desire the production of offspring and not to be
concerned that offspring should be loved" (Cicero, 57F).
However, it is not exactly clear how these various observations are
supposed to offer support for the Stoics' ethical commitments.
Scholarly debate has focused on three main issues. First, how, if at
all, are these apparently descriptive claims able to provide any
normative guidance? Second, how could a natural disposition toward
self-preservation underwrite the other-regarding demands of
cosmopolitan justice? Third, in what ways, if any, is a non-rational
creature's pursuit of food, shelter, and other things favorable
to their non-rational constitution analogous to the Sage's
attachment to virtue as the sole good? It is worth noting that one of
our main sources on *oikeiosis* concludes with an account
of the *ideal* agent's development, culminating in her
appreciation that consistency [or agreement, *homologia*] and
harmony of conduct is the only true source of benefit in a human life
(Cicero, 59D). Magrin 2018 and Klein 2016 take up these issues with
admirable clarity and should be consulted for further details; they
also provide an up-to-date bibliography on this wide-ranging
topic.


### 4.7 Passions



The Stoics famously argue that the virtuous agent feels no passions
(*pathe*) and, so, that the happy life is entirely
passion-free (*apathes*). To better understand this
striking and notorious claim, let us examine how they define the
passions:



> 
> 
> They [the Stoics] say that passion is impulse which is excessive and
> disobedient to the dictates of reason, or a movement of soul which is
> irrational and contrary to nature; and that all passions belong to the
> soul's commanding-faculty. (Stobaeus, 65A)
> 
> 
> 



Notice that all passions are impulses (*hormai*) of a certain
kind, i.e. psychological events directly prefiguring action, which
"belong to the soul's commanding-faculty". This
implies that all passions are "rational impulses", in the
Stoic scheme (Stobaeus, 53Q), insofar as they are created through the
exercise of the agent's rational mind (his
"commanding-faculty"), specifically, through an act of
assent (see
 2.9
 above). Passions are therefore "irrational" and
"disobedient to the dictates of reason" not because they
arise in some part of the mind that lacks reason (like Plato's
spirit or appetite), for the Stoics deny that the human mind has any
non-rational parts. In what sense, then, do the passions disobey the
dictates of reason and count as irrational?



One answer is that, in undergoing a passion, the agent disobeys
*right* reason, i.e. the rationality of the cosmos or the
universal law of Zeus. To suffer a passion is to be in conflict with
nature - to experience "fluttering" rather than the
"good flow" of the happy person (Stobaeus, 65A; cf.
Stobaeus, 63A) - and is therefore a vicious action *par
excellence*, one that frustrates the agent's progress
towards the *telos*. To see why, we need to introduce further
aspects of the Stoic account of passions.



Insofar as each passion follows upon the agent's act of assent,
it is amenable to a cognitivist analysis. According to the Stoics,
each passion can be described as an opinion or judgment or weak
supposition (65B-D), whose content includes two elements, both of
which (in the standard case) are false: (i) an ascription of value to
an object that is present or in prospect and (ii) an assessment that a
particular course of action is appropriate to perform in response
(Graver 2007, ch. 2; Brennan 2005, ch. 7; Inwood 1985, ch. 5). In
standard cases, (i) is false because the passionate agent mistakes
something he currently possesses or expects to possess as either good
or bad, when really it is indifferent. So, for instance, the distress
I feel in learning that I have heart disease involves my mind's
assent to the proposition that illness is both present and something
bad - where "bad" carries the eudaimonist
connotation of being deleterious to my happiness (Cooper 1999b). This
thought is false, of course: disease is dis-preferred, but not bad,
and its presence makes no difference to my happiness. My case of
distress, then, involves a cognitive failure, according to the Stoics:
in suffering this passion, I have incorrectly evaluated illness and
misjudged its connection to my own personal flourishing. As part of my
distress, I may also experience anxious internal constricting and
start to weep, as a result of my mind's assessment that such
actions are appropriate responses to my present illness (element (ii)
above). On the Stoic view, this assessment is also false, for these
are not objectively appropriate reactions to the presence of something
bad (cf. the more complicated Alcibiades case, discussed by Graver
2007, ch. 9).



Distress is one of four main types or genera of passion recognized by
the Stoics. Each type is distinguished by the character of its
intentional object: distress, a present perceived bad; fear, a future
perceived bad; appetite, a future perceived good; delight (or
pleasure), a present perceived good. Appetite and fear are primary,
with distress and delight secondary (Stobaeus, 65A). What is common in
all four genera, however, is a cognitive mistake on the part of the
agent concerning the value of the intentional object or concerning the
appropriate behavioral response - an epistemic failure that is
incompatible with living in agreement with nature. This is one
important upshot of Chrysippus' runner analogy (in Galen, 65J).
Just as a runner moves in such a way that he is "carried
away" and cannot immediately come to a halt, so the passionate
agent acts on impulses "going beyond the rational
proportion", i.e. contrary to the right reason of Zeus (Inwood
1985). However, some commentators see the runner analogy as gesturing
at a sense in which, for Chrysippus, the passionate agent disobeys her
*own* reason as well (Graver 2007, ch. 3). If so, then perhaps
the Chrysippean theory can recognize some form of occurrent mental
conflict after all, although the details of such an interpretation
have not yet been worked out.



Scholars are divided on how exactly to understand Posidonius'
reaction to the Chrysippean account of the passions. From the verbatim
remarks and paraphrases in Galen (65K, M, P, Q), it seems clear that
Posidonius considered some elements of the Chrysippean account
inadequate, but whether Posidonius chose merely to emphasize different
aspects of that account, without substantially revising it, or instead
intended to modify some of its tenets, remains the subject of debate:
see Lorenz 2011 and Cooper 1999b.



In characterizing the ideal human agent as passion-free, what exactly
are the Stoics denying to her? One might suppose that this ideal
implies the eradication of all emotional feelings whatsoever, but the
Stoic account of the virtuous person's "good
feelings" (*eupatheiai*) belies the caricature of the
Sage as an unfeeling robot (Diogenes Laertius, 65F). Whereas passions
are typically directed at indifferents incorrectly judged to be good
or bad, the Sage's good feelings are emotional responses to
genuine goods, i.e. to virtue, virtuous actions, and virtuous friends
(see Graver 2007, ch. 2, and Cooper 2005). Moreover, at some point in
the school's history, the Stoics introduced a category of
feelings called "pre-emotions" (*propatheiai*),
emotional reactions that occur without the intervention of assent and
so able to be experienced by the Sage without compromising the
knowledge in which her virtue consists (Gellius, 65Y; for discussion,
see Graver 2007, ch. 4).


## 5. Influence


### 5.1 On Grammatical Writers



Whether "grammar" was properly speaking a subdiscipline of
Stoic philosophy is debated, but it is generally agreed that Stoic
philosophy of language heavily influenced the works of Ancient
Grammarians. There had long been interest in the study of language,
but the Stoics, and Chrysippus chief among them, with their systematic
study of language, are considered by many to have laid the foundations
for what became the independent discipline of technical grammar. The
Stoic influence can be traced in various works, and Stoic views
(sometimes attributed to "the philosophers") are
explicitly discussed in Scholia, especially to Dionysius Thrax's
*Art of Grammar*. More notably, a debt to the Stoics is
acknowledged by Apollonius Dyscolus, a highly influential second
century CE Greek grammarian, one of the earliest grammarians for whom
we have extant works. Stoic influences can similarly be found in
Priscian, a Latin grammarian of the 6th century CE living in
Constantinople, whose *Institutiones Grammaticae*, in part
based on Apollonius Dyscolus' work, provided much of the
foundation for medieval grammar. The extent and exact nature of this
Stoic influence on the grammatical tradition has, however, been the
subject of considerable debate. On the interactions of grammar and
philosophy, see Lallot 1988, Sluiter 1990, Ildefonse 1997, Swiggers
and Wouters 2002, Atherton and Blank 2013; on the Stoics specifically,
see Frede 1977, Atherton and Blank 2003; on Apollonius Dyscolus, Blank
1982, 2000; and on Latin grammar and Priscian, Baratin 1989, Luhtala
2005, Baratin et al. 2009, Ebbesen 2009.


### 5.2 On Christian Writers



Christian writers were receptive to some elements of Stoicism. There
exists an inauthentic correspondence between St Paul and Seneca
included in the Apocrypha. This forgery is a very ancient one, since
it was referred to in both Jerome (*De Viris Illustribus* 12)
and Augustine (*Epistle* 153.4). But the fact that the letters
were not written by Paul or by Seneca does not mean that Paul was
unaware of Stoic philosophy, nor that his own thought may not be
understood in relation to Stoic theory, cf. Engberg-Pedersen 2000. The
tradition of theories of natural law in ethics seems to stem directly
from Stoicism. (Compare Cicero, *De Legibus* 1.18 with later
writers like Aquinas in *Summa Theologica* II, 2, q. 94.)
Augustine chose to follow the Stoics rather than the Platonists (his
usual allies among the philosophers) on a number of points, including
on the question of animals' membership in the moral community
(*City of God* 1.20) and in his philosophy of language. Sorabji
2000, part IV, argues that the Stoic idea of freedom from the passions
was adapted and transmuted into the idea of seven deadly sins by
Evagrius. In general, see Colish 1985 for the presence of Stoicism in
Latin writers through the sixth century.



The influence of Stoicism on Medieval thought has been considered by
Verbeke 1983. In general, the handling of Stoic ideas in the context
of Christian orthodoxy required a certain delicacy. While it was
agreed by nearly all that God was not a material being, the state of
the human soul was a more controversial matter. In general, ancient
Christian orthodoxy evolved away from materialist anthropology of the
sort found in Tertullian to the immaterialist notion of the soul that
present-day Christians take for granted. Medieval Christians felt it
necessary to reject what they called Stoic fatalism, but notions of
conscience and natural law had clear connections with Stoic
thought.


### 5.3 On Renaissance and Early Modern Philosophy



The late 16th and early 17th centuries saw efforts to form a
systematic synthesis of Christianity and Stoicism. The most important
figure in the Neo-Stoic movement was
 Justus Lipsius.
 The influence of the Hellenistic schools generally on early modern
philosophy is the theme of the essays collected in Miller and Inwood
2003. See also Osler 1991 and Strange and Zupko 2004.


### 5.4 On Contemporary Philosophy



While Stoic texts were not widely read or readily accessible in the
19th and early 20th centuries, some of their views were presented in
anthologies and historical surveys, such as Prantl's 1855
*History of Western Logic*, the first volume of which contains
a lengthy chapter on Stoic logic. A recent study by S. Bobzien (2021)
has suggested that the latter might have found its way to Gottlob
Frege, the 20th century philosopher credited by many with founding
analytic philosophy. In this work, Bobzien produces evidence that some
of Frege's own work is derived from, and heavily indebted to,
these Stoic texts.