Ancient Greek Philosophy

1. Presocratics

Our western philosophical tradition began in ancient Greece in the 6th
century BCE. The first philosophers are called "Presocratics" which
designates that they came before Socrates. The Presocratics were from
either the eastern or western regions of the Greek world. Athens —
home of Socrates, Plato and Aristotle — is in the central Greek region
and was late in joining the philosophical game. The Presocratic's most
distinguishing feature is emphasis on questions of physics; indeed,
Aristotle refers to them as "Investigators of Nature". Their
scientific interests included mathematics, astronomy, and biology. As
the first philosophers, though, they emphasized the rational unity of
things, and rejected mythological explanations of the world. Only
fragments of the original writings of the presocratics survive, in
some cases merely a single sentence. The knowledge we have of them
derives from accounts of early philosophers, such as Aristotle's
Physicsand Metaphysics, The Opinions of the Physicists by Aristotle's
pupil Theophratus, and Simplicius, a Neoplatonist who compiled
existing quotes.

The first group of Presocratic philosophers were from Ionia. The
Ionian philosophers sought the material principle (archê) of things,
and the mode of their origin and disappearance. Thales of Miletus
(about 640 BCE) is reputed the father of Greek philosophy. He declared
water to be the basis of all things. Next came Anaximander of Miletus
(about 611-547 BCE), the first writer on philosophy. He assumed as the
first principle an undefined, unlimited substance (to apeiron)itself
without qualities, out of which the primary opposites, hot and cold,
moist and dry, became differentiated. His countryman and younger
contemporary, Anaximenes, took for his principle air, conceiving it as
modified, by thickening and thinning, into fire, wind, clouds, water,
and earth. Heraclitus of Ephesus (about 535-475 BCE) assumed as the
principle of substance aetherial fire. From fire all things originate,
and return to it again by a never-resting process of development. All
things, therefore, are in a perpetual flux. However, this perpetual
flux is structured by logos– which most basically means 'word,' but
can also designate 'argument,' 'logic,' or 'reason' more generally.
The logos which structures the human soul mirrors the logos which
structures the ever-changing processes of the universe.

Philosophy was first brought into connection with practical life by
Pythagoras of Samos (about 582-504 BCE), from whom it received its
name: "the love of wisdom". Regarding the world as perfect harmony,
dependent on number, he aimed at inducing humankind likewise to lead a
harmonious life. His doctrine was adopted and extended by a large
following of Pythagoreans, including Damon, especially in Lower Italy.

That country was also the home of Eleatic doctrine of the One, called
after the town of Elea, the headquarters of the school. It was founded
by Xenophanes of Colophon (born about 570 BCE), the father of
pantheism, who declared God to be the eternal unity, permeating the
universe, and governing it by his thought. His great disciple,
Parmenides of Elea (born about 511), affirmed the one unchanging
existence to be alone true and capable of being conceived, and
multitude and change to be an appearance without reality. This
doctrine was defended by his younger countryman Zeno in a polemic
against the common opinion, which sees in things multitude, becoming,
and change. Zeno propounded a number of celebrated paradoxes, much
debated by later philosophers, which try to show that supposing that
there is any change or multiplicity leads to contradictions.

Empedocles of Agrigentum (born 492 BCE) appears to have been partly in
agreement with the Eleatic School, partly in opposition to it. On the
one hand, he maintained the unchangeable nature of substance; on the
other, he supposes a plurality of such substances — i. e. the four
elements, earth, water, air, and fire. Of these the world is built up,
by the agency of two ideal principles as motive forces — namely, love
as the cause of union, strife as the cause of separation. Empedocles
was also the first person to propound an evolutionary account of the
development of species.

Anaxagoras of Clazomenae (born about 500 BCE) also maintained the
existence of an ordering principle as well as a material substance,
and while regarding the latter as an infinite multitude of
imperishable primary elements, qualitatively distinguished, he
conceived divine reason or Mind (nous) as ordering them. He referred
all generation and disappearance to mixture and resolution
respectively. To him belongs the credit of first establishing
philosophy at Athens, in which city it reached its highest
development, and continued to have its home for one thousand years
without intermission.

The first explicitly materialistic system was formed by Leucippus
(fifth century BCE) and his pupil Democritus of Abdera (born about 460
BCE). This was the doctrine of atoms — literally 'uncuttables' — small
primary bodies infinite in number, indivisible and imperishable,
qualitatively similar, but distinguished by their shapes. Moving
eternally through the infinite void, they collide and unite, thus
generating objects which differ in accordance with the varieties, in
number, size, shape, and arrangement, of the atoms which compose them.

The efforts of all these earlier philosophers had been directed
somewhat exclusively to the investigation of the ultimate basis and
essential nature of the external world. Hence their conceptions of
human knowledge, arising out of their theories as to the constitution
of things, had been no less various. The Eleatics, for example, had
been compelled to deny that senses give one any access to the truth,
since to the world of sense, with its multitude and change, they
allowed only a phenomenal existence. However, reason can give one
knowledge of what the One is like–or, more accurately, what it is not
like.

Retaining the skepticism of the Eleatics about the senses, while
rejecting their doctrines about the ability of reason to reach truth
apart from the senses, the Sophists held that all thought rests solely
on the apprehensions of these senses and on subjective impression, and
that therefore we have no other standards of action than convention
for the individual. Specializing in rhetoric, the Sophists were more
professional educators than philosophers. They flourished as a result
of a special need for at that time for Greek education. Prominent
Sophists include Protagoras, Gorgias, Hippias, and Prodicus.
2. Socrates and his Followers

A new period of philosophy opens with the Athenian Socrates (469-399
BCE). Like the Sophists, he rejected entirely the physical
speculations in which his predecessors had indulged, and made the
thoughts and opinions of people his starting-point; but whereas it was
the thoughts of and opinions of the individual that the Sophists took
for the standard, Socrates questioned people relentlessly about their
beliefs. He tried to find the definitions of the virtues, such as
courage and justice, by cross-examining people who professed to have
knowledge of them. His method of cross-examining people, the elenchus,
did not succeed in establishing what the virtues really were, however;
they simply exposed the ignorance of his interlocutors.

Socrates was an enormously magnetic figure, who attracted many
followers, but he also made many enemies. Socrates was executed for
corrupting the young of Athens and for disbelieving in the gods of the
city. This philosophical martyrdom, however, simply made Socrates an
even more iconic figure than would have been otherwise, and many later
philosophical schools took Socrates as their hero.

Of Socrates' numerous disciples many either added nothing to his
doctrine, or developed it in a one-sided manner, by confining
themselves exclusively either to dialectic or to ethics. Thus the
Athenian Xenophon contented himself, in a series of writings, with
exhibiting the portrait of his master to the best of his
comprehension, and added nothing original. The Megarian School,
founded by Euclides of Megara, devoted themselves almost entirely to
dialectic investigation of the one Good. Stilpo of Megara became the
most distinguished member of the school. Ethics predominated both with
the Cynics and Cyrenaics, although their positions were in direct
opposition. Antisthenes of Athens, the founder of the Cynics,
conceived the highest good to be the virtue which spurns every
enjoyment. Cynicism continued in Greece with Menippus and on to Roman
times through the efforts of Demonax and others. Aristippus of Cyrene,
the founder of the Cyrenaics,considered pleasure to be the sole end in
life, and regarded virtue as a good only in so far as it contributed
to pleasure.
3. Plato

Both aspects of the genius of Socrates were first united in Plato of
Athens (428-348 BCE), who also combined with them many the principles
established by earlier philosophers, and developed the whole of this
material into the unity of a comprehensive system. The groundwork of
Plato's scheme, though nowhere expressly stated by him, is the
threefold division of philosophy into dialectic, ethics, and physics;
its central point is the theory of forms. This theory is a combination
of the Eleatic doctrine of the One with Heraclitus's theory of a
perpetual flux and with the Socratic method of concepts. The multitude
of objects of sense, being involved in perpetual change, are thereby
deprived of all genuine existence. The only true being in them is
founded upon the forms, the eternal, unchangeable (independent of all
that is accidental, and therefore perfect) types, of which the
particular objects of sense are imperfect copies. The quantity of the
forms is defined by the number of universal concepts which can be
derived from the particular objects of sense.

The highest form is that of the Good, which is the ultimate basis of
the rest, and the first cause of being and knowledge. Apprehensions
derived from the impression of sense can never give us the knowledge
of true being — i.e. of the forms. It can only be obtained by the
soul's activity within itself, apart from the troubles and
disturbances of sense; that is to say, by the exercise of reason.
Dialectic, as the instrument in this process, leading us to knowledge
of the ideas, and finally of the highest idea of the Good, is the
first of sciences (scientia scientiarum). In physics, Plato adhered
(though not without original modifications) to the views of the
Pythagoreans, making Nature a harmonic unity in multiplicity. His
ethics are founded throughout on the Socratic; with him, too, virtue
is knowledge, the cognition of the supreme form of the Good. And since
in this cognition the three parts of the soul — cognitive, spirited,
and appetitive — all have their share, we get the three virtues:
Wisdom, Courage, and Temperance or Continence. The bond which unites
the other virtues is the virtue of Justice, by which each several part
of the soul is confined to the performance of its proper function.

The school founded by Plato, called the Academy (from the name of the
grove of the Attic hero Academus where he used to deliver his
lectures) continued for long after. In regard to the main tendencies
of its members, it was divided into the three periods of the Old,
Middle, and New Academy. The chief personages in the first of these
were Speusippus (son of Plato's sister), who succeeded him as the head
of the school (till 339 BCE), and Xenocrates of Chalcedon (till 314
BCE). Both of them sought to fuse Pythagorean speculations on number
with Plato's theory of ideas. The two other Academies were still
further removed from the specific doctrines of Plato, and advocated
skepticism.
4. Aristotle

The most important among Plato's disciples is Aristotle of Stagira
(384-322 BCE), who shares with his master the title of the greatest
philosopher of antiquity. But whereas Plato had sought to elucidate
and explain things from the supra-sensual standpoint of the forms, his
pupil preferred to start from the facts given us by experience.
Philosophy to him meant science, and its aim was the recognition of
the purpose in all things. Hence he establishes the ultimate grounds
of things inductively — that is to say, by a posteriori conclusions
from a number of facts to a universal. In the series of works
collected under the name of Organon, Aristotle sets forth the laws by
which the human understanding effects conclusions from the particular
to the knowledge of the universal.

Like Plato, he recognizes the true being of things in their concepts,
but denies any separate existence of the concept apart from the
particular objects of sense. They are inseparable as matter and form.
In matter and form, Aristotle sees the fundamental principles of
being. Matter is the basis of all that exists; it comprises the
potentiality of everything, but of itself is not actually anything. A
determinate thing only comes into being when the potentiality in
matter is converted into actuality. This is effected by form, inherent
in the unified object and the completion of the potentiality latent in
the matter. Although it has no existence apart form the particulars,
yet, in rank and estimation, form stands first; it is of its own
nature the most knowable, the only true object of knowledge. For
matter without any form cannot exist, but the essential definitions of
a common form, in which are included the particular objects may be
separated from matter. Form and matter are relative terms, and the
lower form constitutes the matter of a higher (e.g. body, soul,
reason). This series culminates in pure, immaterial form, the Deity,
the origin of all motion, and therefore of the generation of actual
form out of potential matter.

All motion takes place in space and time; for space is the
potentiality, time the measure of the motion. Living beings are those
which have in them a moving principle, or soul. In plants the function
of soul is nutrition (including reproduction); in animals, nutrition
and sensation; in humans, nutrition, sensation, and intellectual
activity. The perfect form of the human soul is reason separated from
all connection with the body, hence fulfilling its activity without
the help of any corporeal organ, and so imperishable. By reason the
apprehensions, which are formed in the soul by external
sense-impressions, and may be true or false, are converted into
knowledge. For reason alone can attain to truth either in cognition or
action. Impulse towards the good is a part of human nature, and on
this is founded virtue; for Aristotle does not, with Plato, regard
virtue as knowledge pure and simple, but as founded on nature, habit,
and reason. Of the particular virtues (of which there are as many as
there are contingencies in life), each is the apprehension, by means
of reason, of the proper mean between two extremes which are not
virtues — e.g. courage is the mean between cowardice and
foolhardiness. The end of human activity, or the highest good, is
happiness, or perfect and reasonable activity in a perfect life. To
this, however, external goods are more of less necessary conditions.

The followers of Aristotle, known as Peripatetics (Theophrastus of
Lesbos, Eudemus of Rhodes, Strato of Lampsacus, etc.), to a great
extent abandoned metaphysical speculation, some in favor of natural
science, others of a more popular treatment of ethics, introducing
many changes into the Aristotelian doctrine in a naturalistic
direction. A return to the views of the founder first appears among
the later Peripatetics, who did good service as expositors of
Aristotle's works.

The Peripatetic School tended to make philosophy the exclusive
property of the learned class, thereby depriving it of its power to
benefit a wider circle. This soon produced a negative reaction, and
philosophers returned to the practical standpoint of Socratic ethics.
The speculations of the learned were only admitted in philosophy where
serviceable for ethics. The chief consideration was how to popularize
doctrines, and to provide the individual, in a time of general
confusion and dissolution, with a fixed moral basis for practical
life.
5. Stoicism

Such were the aims of Stoicism, founded by Athens about 310 by Zeno of
Citium (in Cyprus), and brought to fuller systematic form by his
successors a heads of the school, Cleanthes of Assos, and especially
Chrysippus of Soli, who died about 206. Important Stoic writers of the
Roman period include Epictetus and Marcus Aurelius. Their doctrines
contained little that was new, seeking rather to give a practical
application to the dogmas which they took ready-made from previous
systems. With them philosophy is the science of the principles on
which the moral life ought to be founded. The only allowable effort is
towards the attainment of knowledge of human and divine things, in
order to thereby regulate life. The method to lead men to true
knowledge is provided by logic; physics embraces the doctrines as to
the nature and organization of the universe; ethics draws from them
its conclusions for practical life. Regarding Stoic logic, all
knowledge originates in the real impressions of things on the senses,
which the soul, being at birth a blank slate, receives in the form of
presentations. These presentations, when confirmed by repeated
experience, are syllogistically developed by the understanding into
concepts. The test of their truth is the convincing or persuasive
force with which they impress themselves upon the soul.

In physics the foundation of the Stoic doctrine was the dogma that all
true being is corporeal. Within the corporeal they recognized two
principles, matter and force — that is, the material, and the Deity
(logos, order, fate) permeating and informing it. Ultimately, however,
the two are identical. There is nothing in the world with any
independent existence: all is bound together by an unalterable chain
of causation. The agreement of human action with the law of nature, of
the human will with the divine will, or life according to nature, is
virtue, the chief good and highest end in life. It is essentially one,
the particular or cardinal virtues of Plato being only different
aspects of it; it is completely sufficient for happiness, and
incapable of any differences of degree. All good actions are
absolutely equal in merit, and so are all bad actions. All that lies
between virtue and vice is neither good nor bad; at most, it is
distinguished as preferable, undesirable, or absolutely indifferent.
Virtue is fully possessed only by the wise person, who is no way
inferior in worth to Zeus; he is lord over his own life, and may end
it by his own free choice. In general, the prominent characteristic of
Stoic philosophy is moral heroism, often verging on asceticism.
6. Epicureanism

The same goal which was aimed at in Stoicism was also approached, from
a diametrically opposite position, in the system founded about the
same time by Epicurus, of the deme Gargettus in Attica (342-268), who
brought it to completion himself. Epicureanism, like Stoicism, is
connected with previous systems. Like Stoicism, it is also practical
in its ends, proposing to find in reason and knowledge the secret of a
happy life, and admitting abstruse learning only where it serves the
ends of practical wisdom. Hence, logic (called by Epicurus
(kanonikon), or the doctrine of canons of truth) is made entirely
subservient to physics, physics to ethics. The standards of knowledge
and canons of truth in theoretical matters are the impressions of the
senses, which are true and indisputable, together with the
presentations formed from such impressions, and opinions extending
beyond those impressions, in so far as they are supported or not
contradicted by the evidence of the senses. In practical questions the
feelings of pleasure and pain are the tests. Epicurus's physics, in
which he follows in essentials the materialistic system of Democritus,
are intended to refer all phenomena to a natural cause, in order that
a knowledge of nature may set men free from the bondage of disquieting
superstitions.

In ethics he followed within certain limits the Cyrenaic doctrine,
conceiving the highest good to be happiness, and happiness to be found
in pleasure, to which the natural impulses of every being are
directed. But the aim is not with him, as it is with the Cyrenaics,
the pleasure of the moment, but the enduring condition of pleasure,
which, in its essence, is freedom from the greatest of evils, pain.
Pleasures and pains are, however, distinguished not merely in degree,
but in kind. The renunciation of a pleasure or endurance of a pain is
often a means to a greater pleasure; and since pleasures of sense are
subordinate to the pleasures of the mind, the undisturbed peace of the
mind is a higher good than the freedom of the body from pain. Virtue
is desirable not for itself, but for the sake of pleasure of mind,
which it secures by freeing people from trouble and fear and
moderating their passions and appetites. The cardinal virtue is
prudence, which is shown by true insight in calculation the
consequences of our actions as regards pleasure or pain.
7. Skepticism

The practical tendency of Stoicism and Epicureanism, seen in the
search for happiness, is also apparent in the Skeptical School founded
by Pyrrho of Elis (about 365-275 BCE). Pyrrho disputes the possibility
of attaining truth by sensory apprehension, reason, or the two
combined, and thence infers the necessity of total suspension of
judgment on things. Thus can we attain release from all bondage to
theories, a condition which is followed, like a shadow, by that
imperturbable state of mind which is the foundation of true happiness.
Pyrrho's immediate disciple was Timon. Pyrrho's doctrine was adopted
by the Middle and New Academies (see above), represented by Arcesilaus
of Pitane (316-241 BCE) and Carneades of Cyrene (214-129 BCE)
respectively. Both attacked the Stoics for asserting a criterion of
truth in our knowledge; although their views were indeed skeptical,
they seem to have considered that what they were maintaining was a
genuine tenet of Socrates and Plato.

The latest Academics, such as Antiochus of Ascalon (about 80 BCE),
fused with Platonism certain Peripatetic and many Stoic dogmas, thus
making way for Eclecticism, to which all later antiquity tended after
Greek philosophy had spread itself over the Roman world. Roman
philosophy, thus, becomes an extension of the Greek tradition. After
the Christian era Pythagoreanism, in a resuscitated form, again takes
its place among the more important systems. Pyrrhonian skepticism was
also re-introduced by Aenesidemus, and developed further by Sextus
Empiricus. But the preeminence of this period belongs to Platonism,
which is notably represented in the works of Plutarch of Chaeronea and
the physician Galen.
8. Neoplatonism

The closing period of Greek philosophy is marked in the third century
CE. by the establishment of Neoplatonism in Rome. Its founder was
Plotinus of Lycopolis in Egypt (205-270) and its emphasis is a
scientific philosophy of religion, in which the doctrine of Plato is
fused with the most important elements in the Aristotelian and Stoic
systems and with Eastern speculations. At the summit of existences
stands the One or the Good, as the source of all things. It emanates
from itself, as if from the reflection of its own being, reason,
wherein is contained the infinite store of ideas. Soul, the copy of
the reason, is emanated by and contained in it, as reason is in the
One, and, by informing matter in itself non-existence, constitutes
bodies whose existence is contained in soul. Nature, therefore, is a
whole, endowed with life and soul. Soul, being chained to matter,
longs to escape from the bondage of the body and return to its
original source. In virtue and philosophic thought soul had the power
to elevate itself above the reason into a state of ecstasy, where it
can behold, or ascend up to, that one good primary Being whom reason
cannot know. To attain this union with the Good, or God, is the true
function of humans, to whom the external world should be absolutely
indifferent.

Plotinus's most important disciple, the Syrian Porphyry, contented
himself with popularizing his master's doctrine. But the school if
Iamblichus, a disciple of Porphyry, effected a change in the position
of Neoplatonism, which now took up the cause of polytheism against
Christianity, and adopted for this purpose every conceivable form of
superstition, especially those of the East. Foiled in the attempt to
resuscitate the old beliefs, its supporters then turned with fresh
ardor to scientific work, and especially to the study of Plato and
Aristotle, in the interpretation of whose works they rendered great
services. The last home of philosophy was at Athens, where Proclus
(411-485) sought to reduce to a kind of system the whole mass of
philosophic tradition, until in 529 CE, the teaching of philosophy at
Athens was forbidden by Justinian.