Find schools and get information on the program that’s right for you.
FEEDBACK (C)1998-2012 All Rights Reserved.
Site last updated 28 October, 2012
History of Philosophy
by Turner, William (S.T.D.) Life. Plato was born at Athens some years after the beginning of
the Peloponnesian War. The exact year of his birth is unknown, but 427
or 428 B.C. is the most probable date. His father's name was Aristo;
his mother, Perictione, was descended from Dropides, a near relative of
Solon. Plato was originally called Aristocles, Platôn
being a nickname given by his master in gymnastics on account of his
Concerning his early life we do not possess much reliable information.
We may, however, presume that he profited by all the educational
advantages that were within the reach of a noble and wealthy Athenian
youth. Zeller calls attention to three circumstances which had a
determining influence on the development of Plato's mind. The first of
these was the political condition of Athens. The city was just then
experiencing the full effects of demagogic rule, and the conditions at
home and abroad were such that the mind of the aristocratic young
student naturally turned towards idealistic schemes of state
organization, schemes which were later to find expression in  The
Republic. The second circumstance is the fact that in early life
Plato devoted much attention to poetry, composing poems of no mean
artistic value. These early studies were not without effect on his
philosophy; they influenced the entire spirit of his system as well as
the language, so remarkable for its grace and beauty, in which that
system was set forth. Indeed, it is true, in a sense, that Plato became
a philosopher without ceasing to be a poet. The circumstance, however,
which was most decisive in determining the life and philosophy of Plato
was the personal influence of Socrates; for though he had studied the
doctrines of Heraclitus under Cratylus, his philosophical training may
be said to date from his first meeting with Socrates.
After the death of Socrates, Plato, who had spent about eight years as
disciple, began his travels preparatory to establishing a school of his
own. He first repaired to Megara, Plato, etc., pp. 7 ff
where some of the disciples of
Socrates were gathered under the leadership of Euclid. Thence he went
to Italy to obtain a more intimate acquaintance with the doctrines of
the Pythagoreans. The exact order of his subsequent journeys is not
certain still, there is no reason to doubt that he visited Egypt,
although the tales that are told of the vast stores of learning which
he acquired in that country are far from reliable. We may accept as
true the story of his journeys to Sicily, and of his relations with the
elder Dionysius, who sold him into slavery, as well as with Dionysius
the younger, whom he tried to convert to his Utopian scheme of state
 Some historians doubt the accuracy of this statement, which rests
on the authority of Hermodorus, a disciple of Plato.
It was after his first journey to Sicily that Plato began his career at
Athens as a teacher. Imitating his master, Socrates, he gathered round
him the young men of the city, but, unlike Socrates, he refused to
teach in the public squares, preferring the retirement of the groves
near the gymnasium of Academus. There he met his disciples, conversing
with them after the manner of Socrates, though it is natural to suppose
that in his style as well as in his choice of illustrations he departed
from the Socratic example of studied plainness. On his return from his
third journey to Sicily, Plato took up his residence permanently in
Athens, and thenceforth devoted himself unremittingly to teaching and
writing. He lived to the age of eighty, dying in the midst of his
intellectual labors. If Cicero's story be true, cf. Zeller,
op. cit., p. 14, note 26.
he died in the act of
writing; according to another tradition prevalent in ancient times, he
died at a wedding feast.
Cf. Cicero, De Senectute, V, 13.
Plato's Character. Even in antiquity, the character of Plato was
violently assailed. His dealings with Socrates and afterwards with his
own disciples, his visits to Sicily, his references to the
philosophical systems of his predecessors, were all made the pretext
for accusations of self-assertion, tyranny, flattery of tyrants,
plagiarism, and willful misrepresentation. His aristocratic ways and
his disdain of the ostentatious asceticism of the Cynics served as the
basis for charges of love of pleasure and immorality. The evidence on
which all these accusations rests is of the flimsiest nature, while, on
the contrary, everything that Plato wrote bears testimony to the lofty
nobility of the man. The truth is that Plato's character was not easily
understood. When the idealism and poetic temperament which were his by
instinct and early training broke loose from the restraint of Socratic
influence, he was merely realizing in his personal character the ideal
of Greek life -- an ideal which, by reason of its many-sidedness, was
a contradiction and a scandal to the narrow-minded advocates of
asceticism and abstemiousness. The importance which Plato attached to a
larger culture was taken by the Cynics and his other adversaries as a
sign that he had abandoned, whereas he was in reality but rounding out
and perfecting, the Socratic idea of what a philosopher ought to be.
Plato's Writings. We are fortunate in possessing all the genuine
works of Plato. The so-called Platonic dialogues which are spoken of as
lost are certainly spurious. The  Divisions mentioned by
Aristotle is neither a Platonic nor an Aristotelian treatise; the
agrapha dogmata, of which Aristotle also makes mention, is most
likely a collection of the views which Plato himsell had not committed
to writing, but which some disciple collected for the use of the
While nothing that Plato wrote has been lost, it is by no means easy to
determine how many of the thirty-six dialogues that have come down to
us are undoubtedly authentic. With respect to Cf. Ueberweg, History of Philosophy, English trans.,
pp. 108 ff.
The Banquet, Gorgias, The Republic, Timaeus, Thaetetus, and
Phaedo , there can be no reasonable doubt. Others, like
Parmenides, Cratylus, The Sophist, are not so certainly genuine;
while in the case of Minos, Hipparchus, etc., the balance of
evidence is against their authenticity.
 The paging employed in citations from Plato's
Next comes the question of the Works is that
of the Stephanus edition (Paris, 1578). This paging is preserved in the
more recent editions, for example, Bekker's (Berlin, 1816-1823),
Didot's (Paris, 1846 ff.), and also in Jowett's translation ( The
Dialogues of Plato, Oxford, 1871; third edition, New York and
London, 1892). For general bibliography, cf. Weber, op.
cit., p. 77, n.; Ueberweg, op. cit., p. x7; to these lists
add Ritchie, Plato (New York, 1902).
order or plan of the
Platonic dialogues. Ueberweg mentions the three principal theories held
by scholars. They are (1) that Plato wrote according to a definite
plan, composing first the elementary dialogues, then the
mediatory, and finally the constructive discourses; (2)
that he had no definite plan, but that the dialogues represent the
different stages in the development of his mind; (3) that he
deliberately portrayed in his dialogues the several stages in the life
of Socrates, the ideal philosopher. Zeller, however, very sensibly
remarks that the question has been argued too much on  a
priori grounds, and suggests that the first thing to do is to
determine the order in which the dialogues were written -- a task that
is by no means easy.
The form of the Platonic writings is, as is well known, the dialogue;
the reasons why Plato adopted this literary form are not far to seek.
In the first place, he was influenced by the Socratic method; secondly,
he was poet enough to recognize the dramatic effect of which the
dialogue is capable, and the room which it affords for local coloring
and portrayal of character. Finally, he must have recognized that the
dialogue afforded him the amplest opportunity of presenting the life of
the model philosopher in the words and acts of the idealized Socrates.
Philosophy was for Plato a matter of life as well as of thought; "true
philosophy, therefore, could only be represented in the perfect
philosopher, in the personality, words, and demeanor of Socrates." Plato, pp. 118 ff.
The Platonic dialogue has been well described as occupying a middle
position between the personal converse of Socrates and the purely
scientific continuous exposition of Aristotle. Plato, adopting a
stricter idea of method than Socrates adopted, excludes the personal
and contingent elements which made the discourse of Socrates so
picturesque; while at times, when he explains the more difficult points
of doctrine, he abandons almost altogether the inductive method for the
deductive, the dialogue well-nigh disappears and gives way to unbroken
discourse. This is especially true of the  Timaeus.
In his use of the dialogue, Plato constantly has recourse to the myth
as a form of expression. The poetical and artistic value of the myth is
conceded by all, but it offers no small difficulty when there is
question of the philosophical doctrine which it was meant to convey.
Whatever may have been Plato's purpose in introducing the myth, --
whether it was to elucidate by concrete imagery some abstract
principle, or to mislead the unthinking populace as to his religious
convictions, or to conceal the contradictions of his thought, striving
to "escape philosophical criticism by seeking refuge in the license of
the poet," -- there can be no doubt that the myth was intended to be a
mere allegory, and Plato himself warns us against taking such
allegories for truth, the shadow for the substance. Cf. Zeller, op. cit., p. 153.
Definition of Philosophy. Plato's philosophy is essentially a
completion and extension of the philosophy of Socrates. What Socrates
laid down as a principle of knowledge, Plato enunciates as a principle
of Being; the Socratic concept, which was
epistemological, is succeeded by the Platonic Idea, which is a
metaphysical notion. Socrates taught that knowledge through concepts is
the only true knowledge; therefore, concludes Plato, the concept, or
the Idea, is the only true reality. Thus, for Plato, philosophy is the
science of the Idea, or, as we should say, of the unconditioned basis
In the Phaedrus Plato describes how the soul, at sight of
singular phenomena, is moved to a remembrance of its heavenly home
and of the archetypes which it contemplated in a previous existence,
and of which it now beholds the imperfect copies. Thereupon, the soul,
falling into an ecstasy of delight, wonders at the contrast between the
Idea (archetype) and the phenomenon (copy), and from this wonder
proceeds the impulse to philosophize, which is identical with the
impulse to love. For, while it is true that there is a contrast between
every Idea and its phenomenon, the contrast is more striking in the
case of the  Idea of the beautiful, this Idea shining through its
visible copies more perfectly than any other Idea. Philosophy, then,
is the effort of the human mind to rise from the contemplation of
visible copies of Ideas to the knowledge of Ideas themselves.
To the question, How is this knowledge of Ideas to be attained? Plato
answers, By means of dialectic -- to this all other training is
preliminary. Plato, moreover, is careful to distinguish between
knowledge ( epistêmê) and opinion
( doxa), -- so that, when he defines philosophy as knowledge, we
must understand him to speak of knowledge in the stricter sense of the
Cf. Gorgias, 454 D; Meno, 97 E.
Division of Plato's Philosophy. Plato, unlike Aristotle, neither
distinguished between the different parts of philosophy, nor made each
part the subject of a separate treatise. Still, the doctrines found in
the dialogues may be classed under the three heads of Dialectic,
Physics, and Ethics -- a division which, according to Cicero, was
made by Plato himself, although it is more probable
that it was first formulated by Xenocrates, as Sextus says. Under
the title  Dialectic it is customary to include not only logic,
but also the doctrine of Ideas. Under the division Physics are
comprised Plato's doctrine concerning the world of phenomena in
general, his teaching regarding the relation between Idea and
phenomenon, his cosmogenetic theories, his notions of matter, space,
and so forth. Finally, under Ethics are included not only
questions which belong to the science of morals, but also the political
doctrines which play so important a part in the Platonic system.
Mathem., VII, 16.
Dialectic. It would be idle to look to Plato for a system of
logic. We find, indeed, that he mentions certain laws of thought, but
he enunciates them as laws of being, making them serve a metaphysical
rather than a logical purpose.  It is owing, perhaps, to this
tendency of Plato's mind towards the metaphysical view that definition
and division receive more of his attention than do the other problems
of logic; dialectic, he teaches, is concerned (as is every part of
philosophy) with the Idea, or, more explicitly, dialectic has for its
object to reduce what is manifold and multiple in our experience of
phenomena to that unity of concept which belongs to a knowledge of
Ideas, and, furthermore, to establish an organic order among the
concepts thus acquired. Dialectic has, therefore, the double task of
defining universal concepts by  induction
( sunagôgê) and classifying them by division
Definition and division together with some remarks on the problem of
language are the only logical doctrines to be found in the dialogues.
Dialectic, however, includes, besides logical doctrines, the theory of
Ideas, which is the center of all Platonic thought; for dialectic is
the doctrine of the Idea in itself, just as physics is the doctrine of
the Idea imitated in nature, or as ethics is the doctrine of the Idea imitated in human action. Under the
title of Cf. Lutoslawski, Origin and Growth of Plato's Logic,
etc. (London, 1897).
 Cf. Phaedo, 100 A; Tim., 28 A.
 Cf. Phaedrus, 265 E.
Dialectic, therefore, the theory of Ideas is studied; it
includes the following questions: (1) origin of the theory of Ideas;
(2) nature and objective existence of the Ideas; (3) their expansion
into plurality: formation of the world of Ideas.
1. Origin of the theory of Ideas. The theory of Ideas, as has
been remarked above, is a natural development of the Socratic doctrine
of concepts. Knowledge, as distinct from opinion, is the knowledge of
reality. Now, Socrates taught that in order to know a thing it is
necessary and sufficient to have a concept of that thing. Therefore,
the concept, or Idea, is the only reality. To deny that the Idea is a
reality is to deny the possibility of scientific knowledge.
Such is the first and most immediate derivation of the theory of Ideas.
Starting from Socratic premises, Plato argues that the theory of Ideas
is the only explanation of the objective value of scientific knowledge.
Elsewhere, however, as in the Cf. Tim., 51.
Philebus, he derives the
doctrine of Ideas from the failure of Heraclitus and the Eleatics to
explain Being and Becoming. Heraclitus was right in teaching that
Becoming exists; he was wrong in teaching that Being does not exist.
The Eleatics, on the contrary, were right in teaching that Being is,
but they were wrong in teaching that Becoming is not. The truth is that
both Being and Becoming exist. When, however, we come to analyze
Becoming we find that it is made up of Being and not-Being.
Consequently, in the changing world around us, that alone is real which
is unchangeable, absolute, one, namely the Idea. For example, the
concrete, changeable just is made up partly of what we would call the
contingent element, the element of imperfection, of not-Being, and
partly of the one immutable Idea, justice, which alone possesses real
being. To say, then, that the Idea of  justice does not exist is
to say that the just (a just man or a just action) is all not-Being and has no reality. And what is
said of justice may be said of any other Idea. The Idea is the core of
reality underlying the surface qualities which are imperfections,
Thus the reality of Being and the reality of scientific knowledge
demand the existence of the Idea, and this Phileb., 54 B.
double aspect of the
Idea is never absent from Plato's thought: the Idea is a necessary
postulate if we maintain, as we must maintain, the reality of
scientific knowledge and the reality of Being. These are the two
roads that lead to the Idea, -- the Socratic doctrine of concepts and
the problem of Being and Becoming, a problem that was stated, though
not satisfactorily solved, by Heraclitus and the Eleatics.
Besides these philosophical principles which led to the theory of
Ideas, there existed in the mind of Plato what may be called a
temperamental predisposition to adopt some such theory as the doctrine
of Ideas and by means of it to explain knowledge and reality; for Plato
was a poet and in him the Cf. Arist., Met., I, 6, 987 a, 29.
artistic sense was always predominant.
He was a Greek of the Greeks, and the Greek even in his mythology loved
clearly cut, firmly outlined forms, definite, visible shapes. It was
natural, therefore, for Plato not merely to distinguish in things the
permanent element which is their Being and the object of our knowledge,
but also to extract, as it were, this element from the manifold and
changeable in which it was embedded, and to hypostatize it, causing it
to stand out in a world of its own, in all its oneness and definiteness
2. The nature and objective existence of the Ideas. From what
has been said, it is clear that the Idea is the element of reality in
things -- the one uniform, immutable element, unaffected by
multiplicity, change, and partial not-Being. The expressions which
Plato uses to describe the Idea always imply one or several of these
attributes. For instance, he calls it
ousia, aidios ousia, ontôs on, pantelôs on, kata tauta
on, aei kata tauta echon akinêtôs, etc. The name,
however, by which the Idea is most commonly designated is eidos,
or idea, which primarily denotes something objective, though in
a secondary sense the Platonic Idea is also an idea in our meaning of
the word, a concept by which the object is known. But whether the Idea
be considered subjectively or objectively, -- and the objective aspect
is always to be considered first, -- it is essentially universal, or,
to use Aristotle's phrase, hen epi pollôn. We may call it
the universal essence if we are careful to dissociate from the
word essence the meaning of something existing in things; for
nothing is clearer than that Plato understood by the Idea something
existing apart from ( chôris) the phenomena which make up
the world of sense. The Idea transcends the world of concrete
existence; it abides in the heavenly sphere, the topos noetos,
where the gods and the souls of the blessed contemplate it. It is
described in the Phaedrus as follows: "Now of the heaven
which is above the heavens no earthly poet has ever sung or ever will
sing in a worthy manner. I must tell, for I am bound to speak truly
when speaking of truth. The colorless and formless and intangible
essence is visible to the mind, which is the only lord of the soul.
Circling this in the region above the heavens is the place of true
knowledge." In  The Banquet the Idea of beauty is described
"beauty only, absolute,  separate, simple, and everlasting."
There can be no doubt, therefore, that Plato separated the world of
Ideas from the world of concrete existence. He hypostatized, so to
speak, the Idea, and it was against this separation
( chôrizein) of the Idea that Aristotle directed his
criticism of Plato's theory. According to Aristotle, the Platonic world
of Ideas is a world by itself, a prototype of the world which
we see, and in this interpretation Aristotle is supported and
sustained by all the later Scholastics. It is no longer seriously
maintained that the Platonic Ideas exist merely in the human mind.
More worthy of consideration is the view of St. Augustine, who,
following the example of early Christian Platonists, identifies the
world of Platonic Ideas with the mind of God. This view,
supported as it is by the authority of some of the greatest of
Christian philosophers as well as by that of the later Platonists and
of all the Neo-Platonists, is not lightly to be set aside. On the other
hand, the statements of Aristotle are explicit, and we must remember
that Aristotle was an immediate disciple of Plato; we have no reason to
suppose that he willfully misrepresented his master in this most
important point, and we have every reason to believe that he was fully
capable of understanding his master's teaching. 
So far the Idea has been described as the objective correlative of our
universal concept; but while the universality of our concepts is a
product of dialectical thought, the universality of the Idea is
 Ibid., 210.
 Met., 1, 9, 990 b; XIII, 4, 1078; Phys., IV, 2, 209
b, et alibi.
 For bibliography, cf. Ritter and Preller, op. cit.,
p. 244, note d.
objective, that is, independent of the human mind. This
objective universality is explained in the Sophist, in which
Plato attacks the Eleatic doctrine of the oneness of Being, maintaining
that the Idea is at the same time  one and many. But how
are the unity and multiplicity of the Idea to be reconciled? Plato
answers that they are reconciled by the community
( koinônia) of concepts. As a concept, for example
Being, is differentiated into its determinations, such as motion and
rest, so in the objective order (as Plato shows in the
Parmenides by a more cogent process of direct argument) the
Idea is identical with another thing (  tauton) and at the same
time is different from other things ( thateron). In this way, we
have unity in plurality and plurality in unity. A
Scholastic would say that the fundamental unity of the subject is not
incompatible with the formal multiplicity of its qualities, and while
this is not precisely
what Plato meant, it is certainly a better illustration of Plato's
meaning than is the Neo-Platonic interpretation, according to which by
Ideas Plato meant numbers. It is, however, very likely that Plato did
not clearly understand how unity and multiplicity could belong to the
Just as Plato attacked the Eleatic doctrine of the oneness of Being so
did he Cf. especially 256.
 Parm., 137.
attack the Eleatic doctrine of immobility.  The Idea is
active, for, if it were inert, it would be capable neither of being
known by us nor of constituting reality; and to cause things to be
known and to constitute their reality are, so to speak, the two
functions of the Idea. Not only is the Idea described as active, but
even as the only true cause. In a remarkable passage,  Socrates is
represented as saying that he was dissatisfied with the speculations of
the Physicists, that he was disappointed in his hope that Anaxagoras
would explain the origin of things, and that he finally discovered that
Ideas are the only adequate causes of phenomena. Aristotle, therefore,
is right in saying  that he knew of no efficient causes in the
doctrine of Plato except Ideas, and thus we are forced to accept
without attempting to explain the Platonic doctrine that Ideas, without
being caused, are causes; that although they are not subject to
Becoming, they are the power by whose agency all phenomena become.
Still, in justice to Plato, it should be remembered that while he
maintains the dynamic function of the Ideas, holding them to be living
powers, he is primarily concerned with their static, or plastic,
function, inasmuch as they are the forms, or types, of existing things.
3. Sophis., 248.
 Phaedo, 96 ff.
 Phaedo, loc. cit.
 Met., I, 9, 991, 992;
De Gen. et Corr., II, 9, 335 b.
The world of Ideas. Plato hardly ever speaks of the Idea, but
always of Ideas in the plural, for there is a world of Ideas. Indeed,
we may say that for Plato there are three worlds: world of concrete
phenomena, the world of our concepts, and the world of Ideas
( kosmos, or topos noêtos). The relation
between the first and third of these worlds will be discussed later
under the head of Physics. The relation between the world of concepts
and the world of Ideas lies in the fact that the former is the faint
reflection of the latter. This is how Plato would describe it; in
modern terminology we should say the world of Ideas is the logical and
ontological prius of the world of concepts. But, however we view
the relation between the two worlds, it cannot be denied that there is
at least a parallelism between them. To every concept
corresponds an Idea, and to the laws of thought which rule the world of
concepts correspond the laws of Being which rule the world of Ideas.
In the first place, just as our concepts are many, the Ideas are many.
Everything has its Idea, -- what is small and worthless as well as
what is great and perfect. Products of art as well as objects of
nature; substances, qualities, relations, mathematical figures, and
grammatical forms, -- all these have their Ideas. That alone has no
Idea which is mere Becoming. The number of Ideas, then, is indefinite.
In the second place, our concepts possess a logical unity, and so in
all the multiplicity of Ideas there is Cf. Parm., 130.
a unity which may be called
organic. The Ideas form a series descending in well-ordered
division and subdivision from the highest genera to the individual, and
it is the task of science to represent this series, -- to descend in
thought from the one to the multiple. Plato himself attempted to
perform this task, naming, as the most universal Ideas,  Being and
not-Being, like and unlike, unity and number, the straight and the
crooked, -- an attempt which suggests on the one hand the ten
opposites of the Pythagoreans and on the other hand the ten
Aristotelian categories. The classification is of course incomplete.
Of greater importance than this incomplete enumeration of the highest
kinds of Ideas is Plato's doctrine of the supremacy of the Thaet., 184, 186.
good. As in the material universe the sun is the
source of light and life, illumining the earth and filling every part
of it with life-producing warmth, so in the supersensible world of
Ideas the Idea of good is the light and life of all the other Ideas
causing them both to be and to be known. But what does Plato mean by
this Idea of good? Is it merely the absolute good, acting as final
cause, the goal of human activity, the ultimate end of all things? If
this were Plato's meaning, the good might be defined as a final cause;
it could not be defined as efficient cause, and it certainly is so
described.  Moreover, in the  Philebus
the good is
identified with divine reason. The only rational interpretation,
therefore, of Plato's doctrine of the good is that by the Idea of good
Plato meant God Himself. It is true that for us who are accustomed to
represent the Deity as a person, it is not easy to realize how Plato
could hypostatize a universal concept and call it God, or how he could
conceive the source of life and energy to be intelligent, and yet
describe it in terms inconsistent with self-consciousness. The correct
explanation seems to be that the relation between personality and
intelligence did not suggest itself to Plato. (Not only he, but the
ancient philosophers in general, lacked a definite notion of what
personality is. Plato, it must be understood, did not deny the
personality of God. Indeed, he often speaks of God as a person. He was
simply unconscious of the problem which suggests itself so naturally
to us, How to reconcile the notion of personality with the Idea of good
which he identified with God?
From the consideration of the Idea of good we are led to the next
division of Plato's philosophy, namely, physics; it was because of his
goodness that God created phenomena. We pass therefore, as it were,
through the Idea of good, from the world of Ideas to the world of
phenomena. Cf. Rep., VI, 508.
 Cf. Rep., loc. cit.
 Phileb., 22 C.
Physics. Under this head are included all the manifestations of
the Idea in the world of phenomena. Now the world
of phenomena is the world of sense-presentation, the region of change
and multiplicity and imperfection and, therefore, of partial not-Being.
It presents a striking contrast to the world of Ideas, which stands "in
viewless majesty" above it, and where there is no change, no
imperfection, no not-Being. Yet these two worlds have something in
common: there is a contact ( koinônia) of the lower
with the higher, for the phenomenon partakes ( metechei) of the
Idea. Thus the  concrete good (good men, good actions)
partakes of the absolute good: a horse or a fire in the concrete
world partakes of the horse-in-itself or of the fire-in-itself which
exists in the world of Ideas. In the Parmenides the
participation is explained to be an  imitation
( mimêsis), the Ideas being prototypes
( paradeigmata) of which the phenomena are ectypes, or
copies ( eidôla). This participation is, however, so
imperfect that in beauty and luster and grandeur the world of phenomena
falls far short of the world of Ideas.
1. Whence, we are forced to ask, comes this imperfection, this partial
not-Being? For answer, Plato is obliged to assume a principle directly
antithetical to the Idea. He does not call this principle
Cf. Arist., Met., I, 6, 987 b, 9.
 Parm., 132 D.
matter, the word hulê being first used in this
sense by Aristotle; and it is a mistake to interpret Plato's thought as
if by the principle of imperfection he meant a material substratum of
existence. The phrase by which it is designated varies in the different
dialogues; it is called, for example, space
( chôra), mass ( ekmageion), receptacle
( pandeches), the unlimited ( apeiron), and,
according to some interpreters, it is not-Being ( mê
on), and the great and small. It is described in the
Timeaus as that in which all things appear, grow up, and decay.
Consequently, it is a negative principle of limitation, more akin to
space than to matter, and Aristotle is right in contrasting  his own
idea of the limiting principle with that of Plato. The so-called
Platonic matter is essentially a negation, whereas in
Aristotle's philosophy negation (  steresis) is but a quality of
The concept of Platonic matter is not easy to grasp. It is a mere form,
yet it is not a form of the mind in any Kantian sense. It is a form
objectively existing, and yet it is not a reality. Plato himself
recognized the difficulty which the concept of the principle of
limitation involved. In the Tim., 48ff.
 Phys., IV, 2, 209b; ibid., 210 a.
Timaeus he tells us that it is
known by a kind of  spurious reason ( logismô
nothô) and is hardly a matter of belief. The
confession does not surprise us, for in this attempt to designate a
limiting principle lies the fatal flaw of the whole Platonic theory. To
derive the limited from the unlimited, the partial not-Being from
Being, is a task which neither Plato nor Spinoza could fulfill
consistently with his first assumptions. Aristotle detected this
weakness in the idealistic monism of Plato, as well as in the
materialistic monism of the early Physicists, and it was in order to
supply the defects of both that he introduced the dualistic concept of
a world which is the outcome of the potential and the actual.
Plato, therefore, failed to account satisfactorily for the derivation
of the sensuous from the supersensuous world. He had recourse, as
Aristotle remarks, Tim., 52.
to such widely different expressions as
 participation, community ( koinônia),
imitation ; but he must have been aware that by these phrases
he evaded rather than solved the real problem. One point, however, is
beyond dispute: Plato assumed that a limiting principle, the source of
all evil, and imperfection, exists. He assumed it, illogically, in
defiance of his doctrine that the Idea is the only reality. He is,
therefore, as one who would be a dualist did his premises allow him to
depart from the monism which is the starting point of all his
2. In order to explain the world of phenomena, Plato was obliged to
postulate, besides the Idea and the principle of limitation, the
existence of a Met., I, 6, 987 b.
world-soul ( Nous), which mediates
between the Idea and matter and is the proximate cause of all life and
order and motion and knowledge in the universe. The universe, he
taught, is a living animal ( zôon ennoun), endowed with the
most perfect and most intelligent of souls, because, as he argues in
the Timaeus, if God made the world as perfect as the nature
of matter (the principle of limitation) would allow, He must have
endowed it with a soul that is perfect. This soul is a perfect harmony:
it contains all mathematical proportions. Diffused throughout the
universe, ceaselessly self-moving according to regular law, it is the
cause of all change and all Becoming. It is not an Idea, for the Idea
is uncaused, universal, all-Being, while the world-soul is derived and
particular and is partly made up of not-Being. Although it is conceived
by a kind of analogy with the human soul, the question whether it is
personal or impersonal never suggested itself to Plato. 
After the general problem of the derivation of the sensuous from the
supersensuous world come the particular questions which belong to what
we call Tim., 30, 35.
 Cf. Zeller, Plato, p. 358.
cosmology. Plato himself informs us that since nature
is Becoming rather than Being, the study of nature leads not to true
scientific knowledge (  epistême), but to belief only
( pistis). Cosmology, therefore, and physical science in general
have a value far inferior to dialectic, which is the science of the
3. As to the Tim., 59 C.
origin of the universe: The so-called Platonic
matter is eternal. The universe, however, as it exists had its origin
in time. This seems to be the natural and obvious sense of Timeus, 28,
although Xenocrates, an immediate disciple of Plato, was of opinion
that Plato taught the temporal origin of the world merely for the sake
of clearness -- to emphasize the fact that it had an origin. Now,
since matter existed from eternity, the universe was not created. From
out the chaos which was ruled by necessity ( anagke), God, the
Demiurgos, or Creator, brought order, fashioning the phenomena in
matter according to
the eternal prototypes, the Ideas, and making the phenomena -- for He
was free from jealousy -- as perfect as the imperfection of matter
would allow. First, He produced the world-soul; then, as the sphere is
the most perfect figure, He formed for this soul a spherical body
composed of fire, air, earth, and water -- substances which Empedocles
had designated as the root principles of the world, and which are now,
for the first time in the history of philosophy, called
elements. The question, Why are the elements four in number?
Plato answers by assigning a teleological as well as a physical
reason, thus exhibiting the two influences, Socratic and
Pythagorean, which more than any other causes contributed to determine
his physical theories. The four elements differ from one another by the
possession of definite qualities; all differences of things are
accounted for by different combinations of the elements themselves --
bodies are light or heavy according as the element of fire, which is
light, or the element of earth, which is heavy, prevails.
4. In his explanation of the Cf. Tim., 31 B.
world-system as it now is, Plato
shows still more evidently the influence of the Pythagoreans, and
especially of Philolaus. Add to this influence the natural tendency
of Plato's mind towards the idealistic and artistic concept of
everything, and the doctrine that  the heavenly bodies are created
gods -- the most perfect of God's creatures, from whose fidelity to
their paths in the firmament man may learn to rule the lawless
movements of his own soul -- will cease to appear out of keeping
with the seriousness of Plato's attempt to solve the problems of human
knowledge and human destiny.
5. In Plato's Cf. ibid., 33 B.
 Cf. ibid.,38 E.
anthropological doctrines the mixture of myth and
science is more frequent and more misleading than in any other portion
of his philosophy. As to the origin of the soul, he teaches
that when the Creator had formed the universe and the stars He
commanded the created gods to fashion the human
body, while He Himself proceeded to form the human soul (or at least
the rational part of it), taking for this purpose the same materials
which He had used to form the world-soul, mixing them in the same cup,
though the mixture was of inferior purity.
Plato rejects Ibid., 41 A
the doctrine that the soul is a harmony of the body,
on the ground that the soul has strivings which are contrary to the
inclinations of sense, and which prove it to be of a nature different
from that of the body. The soul is expressly defined  as a
 self-moving principle. It is related to the body merely as a
causa movens. How, then, did it come to be united to the body?
Plato answers by the "figure," or allegory, in which is conveyed
the doctrine of  preëxistence. In the Timaeus,
however, the mythical form of expression is laid aside, as when, for
example, the soul is said to have been united to the body by virtue
of a cosmic law.
The doctrine of preëxistence gave rise to the doctrine of
Phaedo, 93, 95.
 Phaedrus, 245 C.
 Ibid., 246 ff.
 Timaeus, 41 D.
recollection, although sometimes, as in the Meno, the
previous existence of the soul is proved from the possibility of
learning. The doctrine of recollection implies that in our
supercelestial home the soul enjoyed a clear and unclouded vision of
the Ideas, and that, although it fell from that happy state and was
steeped in the river of forgetfulness, it still retains an indistinct
memory of those heavenly intuitions of the truth; so that the sight of
the phenomena -- mere shadows of the Ideas -- arouses in the soul a
clearer and fuller recollection of what it contemplated in its previous
existence. The process of learning consists, therefore, in recalling
what we have forgotten:  to learn is to remember.
If preëxistence is one pole in the ideal circle of the soul's
existence, Meno, 81.
immortality is the other. The sojourn of the soul in
the world of ever-changing phenomena is but a period of punishment which
ends with the death of the body. Underlying the mythical language in
which Plato conveyed his psychological
doctrines, there is a deep-seated conviction of the reality of the
future life, a genuine belief in the immortality of the soul. Indeed,
Plato is the first Greek philosopher to formulate in scientific
language and to establish with scientific proof an answer to the
question, Does death end all things? Hitherto, the immortality of the
soul had been part of the religious systems of Asia and of Greece; now
it appears for the first time as a scientific thesis, as part of a
purely rational system of philosophy.
The dialogue which deals expressly with the problem of immortality is
the Phaedo; there Socrates is represented by the narrator as
discoursing on the future existence, while the jailer stands at the
door of the prison with the fatal draught in his hand. The arguments
which Socrates uses may be summed up as follows:
1. Opposites generate opposites. Out of life comes death: therefore,
out of death comes life.
2. The soul, being without composition, is akin to the absolutely
immutable Idea. The body, on the contrary, is, by its composition, akin
to things which change. When the body is destroyed, the soul, by virtue
of its affinity to the indestructible, is enabled to resist all decay
and destruction. Phaedo, 70 E.
3. If the soul existed before the body, it is natural to expect that it
will exist after the body. That it existed before the body is proved by
the doctrine of recollection. Op. cit., 78-81.
4. Besides these arguments, the following proof is used by Plato. Op. cit., 72-79.
The dissolution of anything is accomplished by the evil which is
opposed to it. Now, moral evil is the only evil which is opposed to the
nature of the soul; if, then, sin does not destroy the soul, -- as
it certainly does not, -- the reason must be that the soul is
Underlying all the foregoing arguments is the one pivotal thought of
Plato's psychology, that Rep., X, 609.
life necessarily belongs to the
Idea of the soul. This thought is brought out in the last of the
5. An Idea cannot pass into its opposite, -- a Scholastic would say
essences are immutable. An Idea, therefore, which has a definite
concept attached to it excludes the opposite of that concept. Now, life
belongs to the Idea of the soul. Consequently, the soul excludes death,
which is the opposite of life. A dead soul is a contradiction in
The same Phaedo, 103 ff.
ontological argument occurs in Phaedrus, 245,
and it is evidently the chief argument on which Plato bases his
conviction that the soul is immortal. Yet in the Phaedo, after
each of Socrates' listeners has signified his acceptance of the proof,
Socrates is made to agree with Simmias that there is no longer room for
any uncertainty except that which arises from the greatness of the
subject and the feebleness of the human mind.
Closely allied with the doctrine of immortality is the doctrine of
Op. cit., 107.
transmigration of souls and of future retribution. Plato
recognized that immortality involves the idea of future retribution of
some sort, just as the necessity of a future retribution involves
immortality. He did not determine scientifically the precise nature of
retribution in the next life. He was content with adopting the
transmigration myths which he derived from the mysteries. Yet, for
Plato, these myths contained a germ of truth, although the most that
can be safely said is that he seriously maintained the doctrine of
transmigration in a generic sense: the details so carefully set forth
in the Timaeus and in the Phaedo are not to be taken as
part of Plato's scientific thought.
When we speak of immortality we must not imagine that Plato held every
part of the soul to be immortal. He enumerates three parts of the
soul, -- the rational ( logos), the irascible
( thumos), and the appetitive ( epithumia) parts.
These are not faculties or powers of one substance, but parts
( merê) the distinction
of which is proved by the fact that appetite strives against reason,
and anger against reason and appetite. Reason resides in the head;
the irascible soul, the seat of courage, is in the heart; and appetite,
the seat of desire, is in the abdomen. 
Of these three, the rational part alone is immortal. It alone is
produced by God. By maintaining that the soul has parts Plato weakens
his doctrine of immortality and exposes it to many objections. Rep., IV, 436 A.
 Cf. Cicero, Tusculanae Disputationes, I, 20.
Plato in his theory of knowledge bases his distinction of kinds
of knowledge on the distinction of objects. Objects of knowledge are
divided as follows:
Supersensible objects ( Noêton genos)
Ideas ( Ideai)
Mathematical entities ( Mathêmatika)
Sensible objects ( Horaton genos)
Real bodies ( Sômata)
Semblances of bodies ( Eikones)
To this corresponds the division of knowledge: Cf. Rep., VI, 509; Ueberweg, op. cit., p. 122
Supersensible knowledge ( Noêsis)
Intellect ( Nous)
Reason ( Dianoia)
Opinion: sense-knowledge ( Doxa)
Sense-perception ( Pistis)
Imagination ( Eikasia)
Knowledge begins with sense-perception. The senses, however, cannot
attain a knowledge of truth. They contemplate the imperfect copies of
the Ideas; as long as we look upon the objects of sense we are merely
gazing at the shadows of things which, according to the celebrated
Allegory of the Cave, are moving where we cannot see them, namely,
in the world of Ideas from which the soul has fallen. (Yet though the
senseperceived world cannot lead us to a knowledge of Ideas, it can
and does remind us of the Ideas which we saw in a previous existence.
It is by the doctrine of recollection, therefore, that Plato bridges
over the chasm between sense-knowledge and a knowledge of reality.
Phenomena are not the causes, but merely the occasions of our
intellectual knowledge; for in knowledge, as in existence, the
universal, according to Plato, is the  prius of the individual.
The doctrine of the Rep., VII, 514.
freedom of the will assumes a novel phase in
the philosophy of Plato. Plato unequivocally asserts that the will is
free. Not only is freedom of choice a quality of adult human
activity, but it is free choice also that decides our parentage,
hereditary tendencies, physical constitution, and early education, for
all these are the result of actions freely performed during the
previous existence of the soul. Notwithstanding this doctrine of
freedom, Plato  holds the Socratic principle that no one is
Plato's Cf. Rep., X, 617; Tim., 42.
 Tim., 86 D.
physiological doctrines are of interest as serving to
show the futility of attempting to explain the complicated phenomena of
life with such inadequate experimental data as he had at his command.
He was forced by his philosophical principles to neglect observation
and to underestimate sense-knowledge. Aristotle, who attached greater
value to empirical knowledge, was far more successful in his
investigation of natural phenomena.
Ethics. Under this head are included Plato's ethical and
political doctrines. If Plato's physics was styled the study of the
Idea in the world of phenomena, this portion of his philosophy may be
called the study of the Idea in human action and human society. Ethics,
however, is vastly more important than physics in the Platonic system
of thought; for physics is treated as if it were scarcely more than a
science of the apparent, while such is the importance attached to
ethics that Plato's philosophy as a whole has been described as
And the description is true to a certain extent. All Platonic, as well
as Socratic, speculation starts with an inquiry about the good and the
beautiful, and proceeds, in the case of Plato, through the doctrine of
concepts to the theory of Ideas. Nevertheless, while Socratic influence
is more apparent in Plato's ethics than in any other portion of his
philosophy, it is true that the system of ethics in its completed form
is part of the Platonic structure, and is conditioned by the
metaphysics, anthropology, and physics of Plato, as well as by the
Socratic inquiries concerning virtue.
1. The highest good, subjectively considered, is happiness ;
objectively, it is the Idea of good, which, as has been seen, is
identified with God.  Consequently, the aim of man's actions should
be to free himself from the bonds of the flesh, from the trammels of
the body in which the soul is confined, and by means of virtue and
wisdom to become like to God, even in this life.  Here, however,
Plato shows a moderation which presents a striking contrast to the
narrow-mindedness and intolerance of the Cynics as well as to the
sensualism of the Hedonists; for though virtue and wisdom are the chief
constituents of happiness, there is place also for right opinion, art,
and for such pleasures as are genuine and free from passion. 
2. Symp., 204 E.
 Cf. Thaet., 176 A.
 Phaedo, 64 ff.
 Cf. Phileb., 28, 60, 62.
Virtue differs from the other constituents of happiness in
this, that it alone is essential. It is defined as the order,
harmony, and health of the soul, while vice is the contrary condition.
Socrates had identified all virtue with wisdom; Plato merely assigns to
wisdom the highest place among virtues, reducing all virtues to four
supreme kinds, --  wisdom, fortitude, temperance, and
justice. He differs also from Socrates in his attempt to
reduce the idea of virtue to its practical applications. Socrates, as
has been pointed out, based all practical virtue on
expediency; Plato, on the contrary, abandoned the utilitarian view,
and by attaching to virtue an independent value inculcated greater
purity of intention.
3. It is in the Rep., IV, 443.
 Cf. ibid., IV, 441.
State that we find the most important
applications of Plato's doctrine of virtue. Man should aim at being
virtuous, and could, even in his savage condition, attain virtue.
Without education, however, virtue would be a matter of mere chance,
and without the State education would be impossible. While, therefore,
the State is not the aim and end of human action, it is the
indispensable condition of knowledge and Virtue.
Accordingly, Cf. Rep., VI, 490 ff.
the State should have for its object virtue, or, as
we should say, the establishment and maintenance of morality. Now, the
only power that can remove from virtue what is contingent and casual
and can place morality on a firm foundation is philosophy.
Consequently, in the Platonic State, philosophy is the dominant power,
and Plato teaches expressly that "unless philosophers become rulers or
rulers become true and thorough students of philosophy, there will be
no end to the troubles of states and of humanity." The ideal State
is  modeled on the individual soul, for the State is the larger
man. Now, in the soul there are three parts; in the State, therefore,
there are three orders, -- rulers, warriors, and
In the details of his scheme for the government of the ideal State,
Plato is led by his aristocratic tendencies to advocate a system of
Ibid., V, 473.
 Ibid., III, 415.
state absolutism. He abolishes private interests and private
possessions. He sacrifices the individual and the family to the
community. He subordinates marriage and education to the interests of
the State. He acknowledges, however, that his schemes are difficult of
realization, and it is for this reason that in the Laws he
sketches the scheme which, though inferior to the scheme outlined in
The Republic, is nearer to the level of what the average State
Religion and AEsthetics. This title does not, like physics and
ethics, designate a portion of Plato's philosophy. It is merely a
convenient heading under which are grouped the doctrines of Plato
concerning the existence of God and the nature of the beautiful.
1. Religion. Plato, as we have seen, identifies true religion
with philosophy. The highest object of philosophical speculation and
the object of religious worship are one and the same, for philosophy is
a matter of life and love as well as of theoetical thought. Atheism,
therefore, is as irrational as it is impious. The existence of
God is evident from the order and design which Plato recognizes
as existing not only in animal organisms but also in the larger world
of astronomy, in the cosmos whose soul is so much superior to the souls
of animals and of men. Besides this teleological argument Plato makes
use of the argument from efficient cause.  He combats the principles of
the early Physicists, according to whom all things, including reason
itself, came originally from matter. This he considers to be an
inversion of the true sequence; for reason precedes matter and is the
cause of all material motion and of all the processes of matter.
The Divinity is the Absolute Good, the Idea of Goodness. Plato extols
His power, His wisdom, and His all-including knowledge and freely
criticises the prevailing anthropomorphic notions of God. God is
supremely perfect: He will never show Himelf to man otherwise than He
really is; for all lying is alien His nature. He exercises over all
things a Providence which orders and governs everything for the
best; Cf. Phileb., 30.
 Laws, X, 893.
sometimes  Plato speaks of God as a personal Being. Besides
this sovereign Divinity, Plato admits the existence of  subordinate
created gods. It is they who mediate between God and matter, and
fashion the body of man as well as the irrational parts of his
soul. Chief among the created gods are the world-soul, the souls of
the stars, and the demons of ether, air, and water.
With regard to popular mythology, Plato employs the names of the gods;
he speaks of Zeus, Apollo, and the other divinities. But "the existence
of these divinities, as held by the Greeks, he never believed, nor does
he in the least conceal it." Tim., 30.
 As in Tim., 37.
 Tim., 41.
2. Plato, p. 500.
AEsthetics. When we consider the importance of art in the
thought and civilization of Greece, we are surprised at the scant
attention which aesthetics received from Greek philosophers before
Plato. And even Plato, though he concerned himself with the analysis of
the beautiful into its metaphysical constituents, seems to have
overlooked the necessity of a psychological study of the sentiment of
Although the good is the highest of the Ideas, the
beautiful is of greatest interest in philosophy, because it
shines more clearly through the veil of phenomena than does any of the
other Ideas. For the essence of the beautiful is harmony, symmetry, and
order, -- qualities which strike the mind of the intelligent observer
of the world of phenomena, even though he fail to penetrate to the
depths of the phenomenon where the good lies hidden.
By a convenient phrase ( kalokagathon) the Greeks identified the
beautiful with the good. The phrase, however, is capable of two
interpretations. It was commonly understood to mean that the
beautiful is good. Plato, following Socrates, interpreted it to
mean that the good is beautiful. Corporeal beauty, he taught, is
lowest in the scale of beautiful things; next come fair souls, fair
sciences, and fair virtues; highest of all is the pure and absolute
beauty to which none of the grossness of the phenomenon cleaves. Now,
the good is harmonious and symmetrical Being. The good, therefore, is
beautiful, and the phenomenon which partakes of the good partakes in
like manner of the beautiful.
Art has for its object the realization of the beautiful. All human
products are imitations; but while, for example, good actions are
imitations of the Idea of good, and beautiful actions are imitations
of the Idea of the beautiful, works of art are imitations of phenomena,
-- imitations of imitations. Consequently, art is not to be compared
with dialectic, nor with industry, nor with the science of government;
it is merely a pastime intended to afford pleasure and recreation,
-- strange doctrine, surely, for one who was himself a poet! Like
other pastimes, it must be controlled, for art too often flatters the
vulgar taste of the wicked and the base. Plato, accordingly, taught
that all artistic productions, the works of sculptors and painters as
well as those of poets and rhetoricians, should be submitted to
competent judges, to whom should be delegated the authority of the
State; Cf. Symp., 208; Phileb., 64 E.
for rhetoric and all the other arts should be placed at the
service of God, and should be so exercised as to assist the statesman
in establishing the rule of morality. 
Cf. Rep., II, 377; Gorgias, 501 ff.
 Phaedrus, 273. Historical Position. There is scarcely, a portion of Plato's
philosophy which does not betray the influence of his predecessors. The
Socratic principle was his starting point. The Pythagorean school
determined to a large extent his cosmological doctrines as well as his
speculations about the future life. Empedocles, Anaxagoras, and the
Earlier Ionians influenced his cosmogenetic theories and his doctrine
of elements, while Heraclitus, Zeno the Eleatic, and Protagoras the
Sophist contributed each in his own way to the Platonic theory of
knowledge. Yet it goes without saying that Plato was no mere compiler.
He modified even the Socratic teaching before making it part of his
philosophical system, and whatever he derived from those who went
before him he molded and wrought so as to fit it for its place in the
vast philosophical edifice the foundation of which is the theory of
Ideas. This distinctively Platonic theory is the basis on which rests the whole
superstructure of physics, dialectic, ethics, theology, and aesthetics.
It is also the unifying principle in Plato's system of thought. Whether
the problem he discusses be the immortality of the soul, the nature of
knowledge, the conditions of the life after death, the mission of the
State, or the nature of the beautiful, his starting point is always the
Idea. It is, therefore, no exaggeration to say that with the doctrine
of Ideas the entire system of Platonic philosophy stands or falls.
Consequently, our judgment of the value of the contents of Plato's
philosophy must be postponed until we can enter with Aristotle into a
critical examination of the value of the theory of Ideas. But whatever
may be our judgment as to the value of his philosophy, no adverse
criticism can detract from his preeminent claim to the first place
among the masters of philosophical style. Even though we refuse to call
him "profound," we cannot but subscribe to the verdict by which all
ages have agreed to give to him the titles divine and sublime.
Subsequent speculation, subsequent discovery, and subsequent increase
in the facilities for acquiring knowledge have corrected much that
Plato taught and added much to what he said, and yet not a single
master has appeared who could dream of rivaling, not to say excelling,
the literary perfection of his philosophical dialogues. This literary
perfection goes deeper than words. It includes a peculiar charm of
manner, by which Plato lifts us from the sordid world of material
things to a world of exalted types and ennobling ideals. His aim as a
philosopher is to demonstrate that true knowledge and true reality
should be sought, not in the things of earth, but in those of that
other world beyond the heavens, where there is no imperfection, change,
or decay. It is this charm of manner that Joubert had in mind when he
wrote: "Plato shows us nothing, but he brings brightness with him; he
puts light into our eyes, and fills us with a clearness by which all
objects afterwards become illuminated.
He teaches us nothing; but he prepares us, fashions us, and makes us
ready to know all. The habit of reading him augments in us the capacity
for discerning and entertaining whatever fine truths may afterwards
present themselves. Like mountain air, it sharpens our organs and gives
us an appetite for wholesome food."