University of Virginia Library

Search this document 
Dictionary of the History of Ideas

Studies of Selected Pivotal Ideas

collapse sectionII. 
collapse sectionII. 
collapse sectionII. 
collapse sectionVI. 
collapse sectionVI. 
collapse sectionVI. 
collapse sectionVI. 
collapse sectionIII. 
collapse sectionI. 
collapse sectionVI. 
collapse sectionVI. 
collapse sectionI. 
collapse sectionVI. 
collapse sectionVI. 
collapse sectionVI. 
collapse sectionVI. 
collapse sectionVI. 
collapse sectionIV. 
collapse sectionIV. 
collapse sectionII. 
collapse sectionIV. 
collapse sectionV. 
collapse sectionIII. 
collapse sectionVI. 
collapse sectionIII. 
collapse sectionIII. 
collapse sectionV. 
collapse sectionVI. 
collapse sectionIII. 
collapse sectionIII. 
collapse sectionVI. 
collapse sectionVI. 
collapse sectionVI. 
collapse sectionV. 
collapse sectionV. 
collapse sectionVII. 
collapse sectionV. 
collapse sectionI. 
collapse sectionI. 
collapse sectionV. 
collapse sectionVI. 
collapse sectionVII. 
collapse sectionIII. 
collapse sectionIII. 
collapse sectionIII. 
collapse sectionVII. 
collapse sectionIII. 
collapse sectionI. 
collapse sectionIII. 
collapse sectionVI. 
collapse sectionII. 
collapse sectionVI. 
collapse sectionI. 
collapse sectionV. 
collapse sectionIII. 
collapse sectionI. 
collapse sectionVII. 
collapse sectionVII. 
collapse sectionII. 
collapse sectionVI. 
collapse sectionV. 
collapse sectionV. 
collapse sectionI. 
collapse sectionII. 
collapse sectionII. 
collapse sectionIV. 
collapse sectionV. 
collapse sectionV. 
collapse sectionV. 
collapse sectionII. 
collapse sectionII. 
collapse sectionV. 
collapse sectionV. 
collapse sectionIV. 


When E. R. Dodds chose to entitle his 1949 Sather
Lectures “The Greeks and the Irrational,” his intention
was doubtless to present a paradox. For the Greeks
are generally taken to be the discoverers of rationality,
or at least to have made the first giant steps on the
path of rational inquiry into the nature of the universe
and the good life for man. Some such generalization
as this is certainly acceptable. But it is not easy to pick
out and describe those qualities exhibited by extant
Greek writers which entitle them to be called “ra-
tional,” without being vague and trivial. And there is
no single equivalent in Greek for “rationality” such
that one could examine its uses and leave it at that;
the word logos comes near it, but it covers a wider
range of meanings. It seems best therefore to concen-
trate on certain definite topics which fall within the
field, in the knowledge that other quite different arti-
cles might be written under the same heading.

Section I describes some of the stages of the devel-
opment from myth to rationality. The criterion that
has been kept in mind to distinguish rationality is the
presence of reasoned argument for preferring one al-
ternative to others. Section II reviews the theories of
Greek and Roman moralists who, in some way or other,
teach that to be virtuous is to be rational. Section III
discusses theories that find rationality in the cosmos
and in the workings of nature.

There is little space, and the author lacks the
competence, to include other topics which might well
find a place under his heading, such as the origin and
development of logic, the various manifestations of
irrationalism in the Greco-Roman world, such as magic
and astrology, and the “rationalism” of classical Greek
art and architecture.


The earliest surviving Greek literature is in the realm
of myth, in which rationality is not much to be
expected. Even here, however, it has often and cor-
rectly been observed that Greek myth, as compared
with that of other nations, contains a striking degree
of rationality. For example, the powers of the gods in
the Homeric poems, though supernatural, are never-
theless distributed according to a pattern in which
reason can be seen. The cosmogonical myths, too, in
Homer and Hesiod are not so extravagantly inconsist-
ent and fantastic as some of the myths of the Near
East. It is noteworthy that Hesiod's Theogony includes
among the lists of gods several personifications of con-
cepts drawn from human society—Wisdom, Right,
Lawfulness, Justice, Peace.

This may help to explain why it was that the Greeks,
rather than other nations, were the first to put forward
theories about the natural world which could be criti-
cized on rational criteria. The Milesians (Thales,
Anaximander, and Anaximenes) in the sixth century B.C.
explained the origin of the world, not by the mating
of powerful divinities, but as a natural process of
growth from a simple substance to a complex form.
They explained the relationship of the constituent parts
of the world by using analogies drawn from men's
social experience (such as justice or war), or arts and
crafts, in such a way that reasons could be offered for
preferring one theory to another. The Milesians did
not explain what the difference was between their
theories and the stories about the natural world told
in the myths; but it is clear that they operated with
an idea of rationality which was well advanced, even
if not explicitly formulated.

Towards the end of the sixth century, a significant
step forward was taken by Xenophanes of Colophon,
who criticized the theology of the Homeric poems and
Hesiod. The surviving fragments give his criticisms and
assertions without the reasoning. “Homer and Hesiod
attribute all things to the gods that among men are
a shame and a disgrace” (frag. 11). “God is one, greatest
among gods and among men, in no way like men in
form and thought” (frag. 23). “Always he remains in
the same [place], moving not at all, nor is it fitting
for him to move, here, now there” (frag. 26). “If
oxen and horses and lions had hands or could paint
and make things with their hands like men, then they
would paint the forms of gods and make their bodies
each according to their own shapes, horses like horses,
oxen like oxen” (frag. 15). The basis of his criticism
appears to have been that he saw an inconsistency
between the concept of god as something different
from man, and the stories told about the gods, which
made them behave as men do.

Contemporary with Xenophanes, Pythagoras moved
in a new direction to explain the phenomenal world
in terms of a rational structure behind appearances.
“Things are numbers.” It is notoriously hard to know
what was the precise meaning and range of the theory
propounded by the founder of the Pythagorean school;
but he certainly began the way of thought later fol-
lowed by Plato and all mathematical physicists in
seeking for a rational system, expressible in mathe-
matical concepts, which would unify the multifarious
changing appearances presented to the senses. In the
earliest form of this theory, it seems that there was
a demand for extreme simplicity: the whole world was
to be explained without using more than the first few
integers in the number series. It was a piece of bravado
typical of the pre-Socratics to claim that such a vast


and complex object as the cosmos itself could be
reduced to the simplest elements in this way, and so
could be understood by the human mind. It was
Pythagoras, according to one tradition, who used the
word cosmos for the world for the first time, as part
of his claim that there is an orderly pattern in the world
which can be understood and expressed.

In this early period of Greek philosophy, the idea
began to emerge that there is an order, a reasona-
bleness, in the natural world, which somehow corre-
sponds with the human mind. Perhaps the idea was
formulated as early as Anaximenes of Miletus, who
identified the stuff of which the world is made with
the human psyche, saying that both are air. It ap-
pears unmistakably in the work of Heraclitus (ca.
500 B.C.), who professed to be the mouthpiece of
the Logos according to which all things come to pass
(frag. 1).

The earliest fully conscious plea for consistency in
philosophical theory (or at least, the earliest that has
survived) is the poem of Parmenides of Elea, “On
Nature” (Περί Φύσεως; first half of the fifth century).
One of the striking peculiarities of this work is its
mixture of myth and reason. The content is presented
as a revelation that was granted to Parmenides by an
unnamed goddess. But at the same time it is a closely
reasoned argument, and the goddess says “judge by
reason (logos) the hard hitting criticism that I have
spoken” (frag. 7.5). The criticism is aimed at earlier
theories, such as those of the Milesians and Heraclitus,
which asserted of things that they “are and are not.”
Parmenides shows clearly a characteristic that is deeply
rooted in Greek thought: the desire that the words used
to describe the world shall pick out with absolute and
inviolable clarity the objects they are intended to iden-
tify. A statement about something in the world should
state what is the case in such a way that its truth is
not affected by circumstances like change of time or
change of the place of observation or change in the
observer. Parmenides carried this demand so far that
he denied the reality of the changing world. To say
that something “is not” is to say nothing about it, or
rather it is to talk about nothing; and such talk is
nonsensical. Hence one can only say “it is.” But all
descriptions of change must necessarily say that some-
thing (the state of affairs before the change) “is not,”
and hence they all contain this element of nonsense:
“So coming to be is extinguished, and destruction is
unintelligible” (frag. 8.21). He went on to make a sharp
distinction between “the way of truth,” which says only
that “it is, and cannot not be... one, continuous,”
and the “way of seeming,” a deceitful way, in which
there is plurality and variation. It is a distinction very
similar in its intention to Plato's distinction between
the Forms, perfect, unchanging, and intelligible, and
the “unreal” phenomena of the sensible world.

Parmenides was thus led by the exigencies of his
reasoning to reject the evidence of the senses com-
pletely. According to Plato (Parmenides 128d), some
made fun of the argument “by showing that it led to
many absurdities and contradictions”; Parmenides'
pupil, Zeno, then came to the help of his master with
arguments to show that the opponents' supposition that
there is plurality leads to even more absurd conse-
quences. According to this view of them (which is
likely to be historically correct), Zeno's paradoxes had
as their aim a reductio ad absurdum of the proposition
that there are many things in existence. The paradoxes
themselves, e.g., Achilles and the tortoise, the flight
of an arrow, etc., and other reductio ad absurdum
illustrations of change and diversity, are too well
known to need description. They are typical of Eleatic
philosophy as a whole, which succeeded in issuing a
great intellectual challenge to all who wanted to phi-
losophize about the nature of the world. The Eleatics
showed that concepts must be examined with a new
rigor, and inferences must be free from contradictions.

It has sometimes been asserted that the work of the
philosophers of Elea shows the influence of mathe-
maticians, in that the structure of their arguments is
similar to that of mathematics, especially of geometry.
However, the state of mathematics in the fifth century
is very obscure. Some believe that by the middle of
the century (approximately when Zeno was writing),
there already existed a system of geometry in which
theorems were deduced from a few postulates and
axioms, by means of a few explicit rules of inference.
Others claim that the first “Elements” must be put
much nearer the date of Euclid (ca. 300 B.C.). It seems
reasonable to say that to explain the characteristics of
Eleatic philosophy by assuming a connection with
mathematical reasoning is to explain ignotum per

However this may be, the Eleatics, in the earlier
half of the fifth century, adopted in its strongest form
a position that was responsible for both the strengths
and the weaknesses of Greek philosophy; they were
confident that by reasoning or “pure thought” one
might be entitled in theory to ignore and reject the
evidence of sense perception.

We must now look at the growth of consciousness
about method in fields of Greek thought other than

Two of the medical writings attributed to Hippocra-
tes, generally thought to belong to the late fifth cen-
tury, are particularly interesting for their recom-
mendations about method. Airs, Waters, Places begins:
“Whoever wishes to pursue properly the science of


medicine must proceed thus.” The recommendation is
to take careful note of the effects of geographical
conditions and climate upon health. The statement of
these effects is highly dogmatic; but the work shows
clearly a remarkable interest in comparative observa-
tions of different peoples, and a desire to do better
than rely on traditional lore and crude trial and error.
The doctor, says the author, must have a rational the-
ory of health, as affected by environment. The Sacred
is well known for its insistence on natural
causes of the disease in question, and its rejection of
superstitious ideas about its origin and attempts to cure
it by “purifications and incantations.”

Sometimes it has been said that there is a striking
difference between the kind of reasoning employed by
the Hippocratic doctors and that of the early Greek
philosophers (a particularly notable expression of this
view is F. M. Cornford's Principium sapientiae). The
philosophers, it is said, demonstrated a ruthless in-
difference to empirical evidence, and were prepared
to generalize extraordinarily widely on the basis of one
or two observations or ideas. The doctors, on the other
hand, resisted such all-embracing theories and recog-
nized the need for detailed observation and even ex-
periment. The Hippocratic treatise On Ancient Med-
begins with a denunciation of those who base all
their work on a “hypothesis”—“heat, cold, moisture,
dryness, or anything else that they may fancy”—ignor-
ing the professional discoveries and records of earlier
practitioners. However, this is a difference that should
not be overstated. The medical writers denounced the
“hypotheses” of the philosophers, but could not free
themselves from other, equally sweeping and uncon-
trolled, generalizations. Scientific research into an-
atomy, physiology and pathology, controlled by
systematic observation, began rather later, with Aris-
totle and his successors, and the medical writers of
the Hellenistic period, e.g., Erasistratus (third cen-
tury B.C.).

The second half of the fifth century saw the begin-
ning of historiography, and the advance from
straightforward storytelling to a reasoned analysis of
events was dramatically swift. The beginnings of a
critical approach can already be seen in Herodotus,
who wrote: “I must tell what is told me, but I need
not believe it entirely” (7, 152). He does indeed include
some wildly improbable stories in his history, especially
about the more remote regions of the earth; but he
often sounds a note of rational skepticism about what
he has been told. He can sometimes, although not
always, make allowances for a biased source.
Thucydides, by contrast, frames his story largely to
bring out his own analysis of cause and effect, and of
the motives—often the hidden motives—of the partic-
ipants. The idea of applying reason to the explanation
of the conduct of peoples and their leaders is fully
developed in Thucydides.

It is clear that in the second half of the fifth century
the audience for whom the Greek writers wrote be-
came accustomed, very rapidly, to new standards of
rationality in all fields of human creativity. Traditions
once taken on trust were now questioned and criti-
cized. The organization of society and even its religious
institutions became subjects for debate. In Athens at
least, it appears that arguing became a favorite
pastime, and the subject matter might be anything
under the sun.

There is no point in seeking for a simple explanation
of this phenomenon; all that can be done is to mention
some of its manifestations. One was the Sophistic
movement. The Sophists, that is, Protagoras, Hippias,
Prodicus, Antiphon, Thrasymachus, and others less
famous, found that they could earn a living by teach-
ing young men various subjects, especially the art of
public speaking. There had previously been no
organized higher education, and the Sophists found a
ready market. The young men responded with alacrity
to the invitation to join in questioning traditional
beliefs and customs. The Sophists came from many
parts of the Greek world and were widely travelled;
their pupils learnt that the way of life in their own
city-state was not the only one possible. The fact that
there were wide differences in morality among differ-
ent societies suggested that all moral rules might be
questioned and criticized—and rejected if they could
not be rationally defended. The literature of the period
contains many references to the distinction between
nature and custom: some Sophists claimed that the
only universally applicable moral rules were those
imposed by nature; all others were “merely” a matter
of conventional agreement.

Naturally such a widespread questioning of tradition
aroused opposition. Aristophanes' Clouds is a comic
poet's version of the conflict. The pupil of the Sophist
(Aristophanes uses Socrates as the representative of the
Sophists, ignoring certain essential differences) learns
that not Zeus but “Vortex” is the ruler of the world,
he learns to reject the convention of filial obedience,
and he learns to use argument with skillful dexterity
to get what he wants. Much more seriously, there were
several trials in Athens for “impiety,” the most famous
of course being those of Protagoras, Anaxagoras, and
Socrates. The charge against Socrates, according to
Plato's Apology, was that he was “guilty of corrupting
the youth, and of believing not in the gods whom the
state believes in but in other new divinities.” What
lay behind this charge, according to Plato, was the
resentment caused by Socrates' questioning of the tra-
ditional sources of morality, and his encouragement of
his young listeners to do the same.


The literature of the period in which the Sophistic
movement arose (or at least, Athenian literature) shows
one outstanding characteristic: an extraordinary taste
for and skill in argument. The Sophists themselves
taught the technique of arguing both sides of a ques-
tion, as a method of imparting skill in speaking. The
common occurrence of two-sided debates in Greek
tragedy, especially in Euripides, shows the popularity
of this kind of contest. The surviving law court
speeches are of course only a small proportion of the
speeches composed during this time; Athens suffered
from litigation as from some endemic disease. What is
to be noticed in the surviving speeches is an emphasis
on rational argument, on what is “probable” or “rea-
sonable” (eulogon), as opposed to irrational methods
of persuasion, such as swearing oaths or offering one's
slaves to be questioned on the rack.


“Socrates,” Aristotle wrote, “believed all the virtues
to be forms of knowledge, so that to know justice
entails being just; for once we have learnt geometry
and architecture we are geometers and architects”
(Eudemian Ethics, Book 1, Ch. 5, 1216b 7). That this
was truly a belief of Socrates is confirmed by the
portrait of him given in Plato's earlier dialogues. It
is far from clear, however, how the paradox is to be
interpreted. What kind of knowledge is virtue? The
analogy with the arts and crafts suggested by Aristotle
and often used by the Platonic Socrates suggests some
kind of skill derived from practice and instruction. But
the Socratic method illustrated by Plato's dialogues was
rather a search for definitions, conducted as a rule
between two people, by question and answer. Socrates
encouraged his listeners to ask and try to answer such
questions as “What is piety?” (Euthyphro), “What is
courage?” (Laches). The implication is that if one could
give a satisfactory answer, then he would have the
corresponding virtue. “No man willingly, does wrong.”
That is to say, if a man knows what is the right and
virtuous thing to do in given circumstances, he will
do it; failures are due to some kind of ignorance.

The most important feature, perhaps, of Socrates'
belief was that it led to searching inquiries into ethical
concepts and the relations between them, inquiries that
had consistency as their first demand. Socrates in the
Platonic dialogues is often engaged in showing one of
his interlocutors that some proposition advanced by
him is inconsistent with something else that he wants
to assert, or with something that has already been
agreed. A set of propositions about what the virtues
are which was free of such inconsistencies would
apparently constitute the knowledge that makes a man

Plato's elaborate structure upon this Socratic foun
dation is set out in the Republic. The ideal state is
described as wholly devoted to instilling knowledge
into those who will be rulers of the state, and to making
sure that they will always be in a position to bring
their knowledge to bear on the life of the community.
The objects of their knowledge form a far more
integrated structure than Socrates envisaged, and the
method of acquiring it was to be a long and single-
minded educational process far different from the cas-
ual conversation of Socrates and his friends. The
proposals of the Republic are accompanied by an anal-
ysis of the human psyche into three parts: the intellect,
the spirited part, and the appetite. Goodness of char-
acter consists in the subordination of the two “lower”
parts to the intellect, just as the virtue of the state
consists in the subordination of the two lower classes
of citizens, the armed forces and the producers, to the
philosophic rulers. The object of the knowledge thus
enthroned, both in the individual and in the state, is
nothing in the sensible world: it is the eternal Forms
of Plato's theory, “the Good itself,” “Beauty itself,”
accessible only to the eye of reason after a long training
in mathematics and dialectic.

Aristotle differed considerably from Plato in his view
of the place of reason in ethics. He made a distinction
between theoretical reason and practical reason. It was
a mistake, he thought, to expect in ethics the same
kind of precision that is required in the subjects studied
by the theoretical sciences. Ethics deals with individual
cases. Universal propositions are of course possible, and
necessary, but their application to human behavior will
never be direct and simple. The man of practical wis-
dom is one who has much experience of human affairs,
and has learnt how to act both by studying the precepts
and examples of others and by having acted himself.

In spite of this distinction between the theoretical
intellect and practical thought, Aristotle returns in the
end to an almost Platonic evaluation of the life of pure
thought. It turns out that although moral goodness is
not dependent on theoretical knowledge, yet the best
life for man is the life of “theory” or contemplation.
This is because such a life is the most godlike. The
characteristic virtue of man, according to this line of
thought, is the functioning of the highest part of the
soul; plants have only a nutritive and reproductive soul,
animals have this and a sensitive soul in addition, and
only men (and gods) have souls which are also capable
of reasoning. Reason is therefore the highest of men's
faculties, and the exercise of reason is the best life for
a man.

Rationality as a virtue was emphasized most of all
by the Stoic school, beginning in the third century B.C.
and adopted with much enthusiasm by many Roman
thinkers. The Stoics based this emphasis, more thor-
oughly than Aristotle, on a view of man as part of


nature. The rational soul of man was declared to be
part of a universal reason (logos), which interpenetrated
the whole of the cosmos in the form of pneuma. The
proper aim of a man's life was defined as “to live in
accordance with nature”; but since the whole of nature
was directed by the universal reason, this aim could
also be described as living according to reason. In
practice, this ideal, which could probably in theory
be interpreted in an almost infinite variety of ways,
turned out to have two important consequences for
Stoic moral theory. First, it gave substance to the
notion that those actions are morally correct for which
reasons can be given; this played an important part
in shaping the Stoic list of “duties” (officia) and in
determining the Stoics' attitude to them. Secondly, the
very high value placed on reason went along with a
devaluation of the emotions, which were held to be
merely “disturbances of the soul.” The ideal Stoic, the
wise man, is described by Cicero (De finibus 3, 75-76):
once reason has taught him that moral goodness is the
only thing of any real value, he is happy forever; he
is more truly a king than Tarquin, who could not rule
either himself or his people; more truly a leader than
Sulla, who was a leader in vice; more free than anyone,
because his mind is not enslaved by desires and cannot
be chained.


It has already been mentioned that the word “cos-
mos” was first applied to the universe by Pythagoras,
if the traditional story is correct, and that his purpose
was to indicate the orderliness of the universe. From
that time on, two aspects of order fascinated the
philosophers: the regularity of the motions of the stars,
planets, sun, and moon, with the attendant seasons and
seasonal changes on earth; and the evidences of
purposiveness in nature, especially in the structure of
living things. The explanation of these two aspects of
order was a dominating theme in the natural philoso-
phy of the Greco-Roman world.

Anaxagoras (mid-fifth century B.C.) first named Mind
as the originator of the cosmos. It appears, however,
that he used this concept only to explain how the world
was first set in motion, and did not go on to explain
how the cosmic mind organized the cosmos into its
orderly and purposive form. Plato's Timaeus is the first
surviving account of this. He represents the world as
the product of two causes: mind (or reason) and neces-
sity. Mind is put into the world by the divine Demiurge
who created it; necessity is a property of the material
with which he had to work. Mind is responsible for
the orderly and regular features of the cosmos, Neces-
sity, also called “the wandering cause,” for the irregu-
larities of the cosmos.

The Timaeus cosmology is in the form of a myth,
so that it is not easy to know how it is to be interpreted.
Aristotle, however, used a similar distinction, and in
a much more literal way. His model for explanation
of events in the natural world is still human craftsman-
ship, but he is clear, as Plato is not, that this is only
a model, and not to be taken at face value; there is
no craftsman who made the cosmos, because the cos-
mos had no beginning and will have no end. Nature
is like art, in that it is purposive; explanations of the
phenomena of nature will therefore seek first for the
“purpose” or end that they serve. Not everything is
purposive; the rest must be explained as coming from
the “necessity” of matter.

Aristotle's conviction that nature works “for an end”
amounts to a belief in the rationality of the cosmos,
since the end is always what would be chosen if the
natural process were directed by a rational agent.
Aristotle's idea of the activity of god was that he is
perpetually engaged in thinking. Since his god's activ-
ity is the cause of the continuity of motion in the
cosmos, primarily the motion of the stars and other
heavenly bodies and derivatively of the continual in-
terchange of the earthly elements, it might appear that
the rationality of nature could be simply explained as
the deliberate choice of a rational god. But it is clear
that this connection was not made by Aristotle—or at
any rate not in his most mature and serious work on
cosmology. The rational working of nature is simply
a fact; it has always been so, and so it does not call
for any genetic explanation.

The Stoic school came closer to Plato in explaining
the rationality of nature as the work of a rational god.
They went, in fact, as far along this path as it is possible
to go. God is identified as a rational spirit which
permeates, as a physical presence, every part of the
cosmos, and causes all the changes which take place
in the cosmos, according to a providential plan. This
faith in the rationality of everything in nature, backed
up by the collection of evidences (see especially Cicero,
De natura deorum II), was a necessary presupposition
of the Stoic moral doctrine which taught that the right
way to live was “in conformity with nature.”

Let my first conviction be [wrote the Emperor Marcus
Aurelius, Meditations X 6] that I am part of a Whole which
is under Nature's governance; and my second, that a bond
of kinship exists between myself and all other similar parts.
If I bear these two thoughts in mind, then in the first place
... I shall cheerfully accept whatever may be my lot; in
the second place, I shall do nothing which might injure
the common welfare of my fellow parts.... Thus doing,
I cannot but find the current of my life flowing smoothly

(trans. Maxwell Staniforth, Baltimore, 1964).


The Platonists, Aristotelians, and Stoics represent,
for all the considerable differences between them, a
common tradition in their assumption of rationality in
the cosmos. An alternative was offered by the atomists,
first Leucippus and Democritus in the late fifth century,
and later Epicurus and his Roman follower Lucretius.
The atomists did not deny that rational explanations
could be given for natural events; indeed they insisted
on it. But they denied that nature works for an end.
They explained everything as the outcome of collisions
of atoms, moving at random in the infinite void, with
no mind of their own and no god to steer them. They
did not deny the regularities and signs of purposiveness
in the world. They offered the motions of atoms as
an alternative explanation of the regularities; and the
evidences of purpose they explained as having emerged
by natural processes in the course of time, by natural
selection, or trial and error. It is curious that the only
words of Leucippus that survive assert that “nothing
happens at random, but everything from reason (logos)
and necessity.” It can only be supposed that he meant
that every event has an explanation in previous events;
there are no completely spontaneous or uncaused

The atomists attempted to depart from the model
of human reason in talking about the natural world.
But the model had too strong a hold. Their mode of
explanation remained less plausible in the ancient
world than the teleology of Aristotle or the Stoics, and
atomists were on the whole an eccentric minority. The
chief reason for this (apart from the fact that the atomic
theory was wedded to a peculiar moral theory by
Epicurus) was that the theory could not explain the
regularities of the cosmos and the artistry of nature
without any knowledge of elementary laws of motion
and without exact measurement.


Arthur W. H. Adkins, Merit and Responsibility: a Study
in Greek Values
(Oxford, 1960). H. Boeder, “Der frühgriech-
ische Wortgebrauch von Logos und Aletheia,” Archiv für
4 (1959), 82-209. F. M. Cornford,
Principium sapientiae (Cambridge, 1952); see the review by
G. Vlastos, Gnomon, 27 (1955), 65-76. E. R. Dodds, The
Greeks and the Irrational
(Berkeley, 1951). Ludwig
Edelstein, Ancient Medicine (Baltimore, 1967). A.-J.
Festugière, La révélation d'Hermès Trismégiste, Vol. II, Le
dieu cosmique
(Paris, 1949). W. K. C. Guthrie, A History
of Greek Philosophy,
3 vols. (Cambridge and New York,
1962; 1965; 1970). G. S. Kirk, Myth: Its Meaning and
Function in Ancient and Other Cultures
(Cambridge and
Berkeley, 1970), esp. pp. 238-51. Gilbert Murray, Five
Stages of Greek Religion,
3rd ed. (New York, 1951). Wilhelm
Nestle, Vom Mythos zum Logos, 2nd ed. (Stuttgart, 1942).
A. S. Pease, “Caeli enarrant,” Harvard Theological Review,
34 (1941). Max Pohlenz, Die Stoa (Göttingen, 1948). Karl
R. Popper, “Back to the Presocratics,” in his Conjectures
and Refutations
(London and New York, 1962). Gerasimos
Santas, “The Socratic Paradoxes,” Philosophical Review, 73
(1964), 147-64. Bruno Snell, Die Entdeckung des Geistes
(Hamburg, 1948); trans. T. G. Rosenmeyer as The Discovery
of the Mind
(Oxford and Cambridge, Mass., 1953). G.
Vlastos: see Cornford. James L. Walsh, Aristotle's Conception
of Moral Weakness
(New York and London, 1963).


[See also Historiography; Irrationalism; Necessity; Plato-
nism; Pre-Platonic Conceptions; Pythagorean Doctrines,
Harmony; Stoicism.