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Plato (427-327BCE)


Doctrine of the Forms
The Person in the World
Knowledge and World: The Divided Line
Influence on Christianity


The photo at right is of a bust of Plato from the National Archeological Museum in Athens, courtesy of Prof. Mark Anderson (click here to see another picture of Plato).

1. Personal life and family

  • Born 427 BCE in aristocratic family, suspicious of new Athenian democracy
  • Never married or had children
  • Served in the military in war of Athens against Sparta
  • Had frustrated political ambitions (see Republic!)
  • Died 347 BCE

2. Philosophical training

  • Student and friend of Socrates, who died when Plato was 31
  • Travelled widely to learn about the world and different societies
  • Made political contacts in an attempt to realize political ideas
  • Probably began writing dialogues at age 40 or 45

3. Plato’s Academy

  • Founded probably just before 370, when Plato was in his mid-50’s
  • Based in Plato’s house, which was called "Academy"
  • Academy closed by the Emperor Justinian in 529 CE
  • Formal education for young men after their schooling in Athens
  • Syllabus described in book7 of the Republic; distinctively academic rather than oriented to professional careers (eg. in politics)
  • Founding teachers included Theaetetus and Eudoxus
  • Most famous graduate was Aristotle, who came at age 17 and stayed for many years, first as a student, and then as a teacher


For a supremely useful introduction to many of Plato's dialogues, see Prof. Mark Anderson's Approaching Plato: A Guide to the Early and Middle Dialogues.

1. Basic Facts

  • Primarily have popular works; few technical works survived
  • Order is difficult to determine, and a matter of ongoing debate

2. Early period

  • Dialogues with Socratic form: genuine objections and arguments
  • Includes: Lysis, Laches, Euthyphro, Charmides, Hippias Major and Hippias Minor, Ion, Protagoras, Euthydemus, Gorgias, Meno, Thrasymachus (BookI of the Republic)

3. Middle period

  • Abandonment of dialogue, except as mere literary device
  • Elaboration of doctrine of Forms
  • Includes: Timaeus, Philebus, Symposium, Phaedo, rest of Republic. Click here for a picture of an old manuscript of the Symposium.
  • Also includes several non-philosophical works: Critias, Phaedrus

4. Late Period

  • More sophisticated, probably written for colleagues in Academy
  • Includes: Theaetetus, Sophist, Politicus, Parmenides, Laws

Doctrine of the Forms

1. Plato on the Heraclitus-Parmenides controversy over Being and Becoming

While Heraclitus insisted that ultimate reality was constantly changing, Parmenides and the Eleatics argued that ultimately, reality was unified and changeless. The argument for this hinges on the contrast between Non-Being and Being: into which category should Becoming be placed? For Parmenides, in accord with the Greek intuition, Becoming couldn’t be Being, so it had to be placed in the Non-Being category, implying, therefore, that the world (of Becoming) was illusory.

This argument was felt to be a first rate paradox, and all of the pre-Socratic philosophers after the Eleatics tried hard to resolve it. Plato comes up with a decisive and truly powerful solution that hinges on the idea of "degrees of intensity of Being." The real world of changeless Being was extremely intense Being, on this view, whereas the changing world of appearances was lesser Being. This solution allows Plato to speak of both Being and Becoming as "real," though in different senses because different degrees of "realness."

2. Plato’s Hierarchy of Being

Degrees of Being is a difficult concept for us Western, pragmatic moderns, who are more accustomed to thinking of Being as a "yes or no" proposition. We think of degrees of goodness, and perhaps even degrees of organization, but not degrees of being. Yet there are lots of points of view from which it is persuasive.

  • It resolves the Eleatic paradox, as just described.
  • It makes sense of the difference between contingency and necessity. The idea of a house survives the destruction of any actual house, so the idea is more powerful than the thing: it is not subject to the contingencies and accidents of the world of appearances.
  • It makes sense of the moral imperative. We have an idea of Goodness that has often seemed to philosophers to be innate, and indeed this is still so, notwithstanding our awareness of culturally variable conceptions of some aspects of morality. We strive to realize this ideal in our lives, because we are ennobled by such a struggle. How are we to think of this idea? It is superior to any actual instance of goodness, for we judge goodness in the light of this idea. It is changeless and beautiful, far more lovely than our concepts and enactments of goodness ever are. As we engage in the struggle to be good, our souls participate in the idea of the Good; our lives and world are illumined so that we see reality more clearly. This idea of the Good has enormous power and liveliness; it is more real than we are, and our quest to realize the good in our lives and in our societies is a quest to participate in the superior reality of the idea of Goodness. It is because of the higher Being of Goodness that it commands us, and so we speak not of a moral option, but of a moral imperative.
  • It explains the fact that we often make mistakes in interpreting our world. This hazy world of appearances is very hard to make out, and the easiest way to understand how this might be so is to suppose that it is secondary in Being to the world of ideas into which, with effort and discipline, we may enter. [Recall the cave story from Republic.]

3. The Forms

Once the idea of a hierarchy of Being has been made plausible, the plausibility of the Doctrine of Forms follows rather easily. What kinds of things have more Being, and what less? Well, the sensible world has less Being, and ideas are the more Real, the more permanent and powerful, the more fundamental, eternal, good, true, and beautiful.

The world of ideas is perfect and changeless; a dynamic array of rational, awe-inspiring beauty; the siren that captures the heart of a person and transforms them into a philosopher, bound to the world of appearances, but struggling to understand, to see, to envision the beauty and power of the world of the Forms.

A world of Forms makes sense out of the fact that we seem to have innate ideas.

  • Consider one of the arguments from Phaedrus: The idea of equality cannot derive from any actual instances of equality, because there are no truly equal things in our world. Moreover, this idea has a kind of definitiveness that surpasses knowledge of the world. The idea of equality is the standard for judging relations of equality; it is superior, and the actual relations of equality inferior, so we need to suppose that there are perfect Forms modeled by our concepts.
  • Consider the mathematical advances of the Pythagoreans. Mathematics has a definitiveness that surpasses the finest knowledge gained from experience. The construction of the Pythagorean theorem, for instance, cannot be realized in the coarse dimensionality of space and time, yet it possesses an amazing profundity and sureness. This can only be accounted for by supposing that it is a concept formed under the impact of a perfect world of geometrical forms. It is the participation of our soul to some extent in that world of Forms that accounts for the fact that we can imagine something so sure and beautiful even though we cannot realize the construction except coarsely in the sensible world.

The Person in the World

1. Soul

For Plato, the soul is the invisible, rational life principle of a human being.

2. Tri-Partite Soul: Intellect, Spirit (Emotion, Will), Appetite

Plato argues that the human soul has three parts: an intellective (rational) part, a spirited part (having to do with emotion and will), and an appetitive part (having to do with drives and basic impulses).

Different kinds of people can be characterized by the relations among these parts, and an ideal arrangement can also be deduced.

  • Tyrannical Soul: Appetite rules Spirit rules Intellect
  • Democratic Soul: Intellect, Spirit, Appetite have equal influence and importance
  • Oligarchic Soul: Intellect and Appetite influence and are submitted to Spirit (Will)
  • Timocratic (one who grasps for honor) Soul: Appetite for love and recognition influences Spirit and Intellect
  • Philosophical Soul is the ideal: Intellect rules over Spirit, and these two together subdue Appetite. A good image is the soul as chariot: the chariot rider is Intellect (Reason), which directs two horses: Spirit (Will) is the lead horse and Appetite is the off horse.

Knowledge and World: The Divided Line

1. Definitions

Epistemology is the theory of knowledge. (Leading questions are What can we know? and How do we know?)

Ontology is the theory of being. (Leading questions are What exists? and How—in what manner or mode—do things exist?)

2. The Divided Line

Plato had a fairly well developed epistemology and ontology. In fact, his ontology and epistemology are intimately linked. His image of the "Divided Line" expresses both and illustrates the way they are connected.

Object of knowledge

Faculty of knowledge

Form of the Good

Things that simply are and do not change

Value structures (e.g. coherence, elegance)

Dialectic (argument aimed at justifying)

Certain knowledge

Structural forms (independent of world)

Theoretical speculation (logical deduction)

Things that appear and change

Concrete world (contextualized things)

Belief (based on experience)

Probable Belief

Images (including abstracted things)

Imagination (abstracting, integrating faculty)

3. Dualism: Mind and Matter, Non-Sensible and Sensible

The divided line makes very clear the distinction between the sensible and the non-sensible, and expresses Plato's clear valuational preference for the non-sensible. In that realm is to be found the unchanging, ever-being, eternal forms, the things we love in the shadows around us. Matter, it follows, is a lesser stuff that is subdued and elevated by form. This results in a sharp form of dualism that looks down on things material and looks up to things spiritual and rational. The conflict of this idea with the Jewish idea that material creation was declared "good" by God was to prove interesting within Christianity.


1. The Three Waves

Plato advocates three waves of socio-political change in the Republic:

  • Rulers should be intelligent, with soul; no other criteria should be allowed to interfere (eg. sex, money, family, etc.).
  • Rulers should live communally; they should hold no property and no family in private, though the larger population should have both families and property.
  • Rulers, having to be intelligent, should be chosen on the basis of their expertise in philosophy, demonstrated through education; philosophers should rule, and rulers should be philosophers.

2. The Philosopher Monarchs: A Limited Aristocracy of Education

Democracy is inefficient, and wrong-headed. But aristocracies of wealth and lineage are dangerous because of the propensity to corruption. The solution is a limited aristocracy of education. Those that are best educated are best able to lead society.

3. Training to Rule: The Curriculum of the Academy

The curriculum of the Academy is indirectly summarized in the Republic.

  • age 1-10: physical education; utopia begins in the body
  • age 10: rescue children from their families and place them in schools
  • age 11-16: music education to balance and complement physical emphasis; refines character and increases sensitivity to feelings
  • age 16-20: moral training introduced to complement previous studies, which themselves are now greatly intensified
  • age 20: Big Test—practical and theoretical; those that fail go into economic positions such as business, farming, trades, etc.
  • age 20-30: another decade of physical, intellectual, moral education
  • age 30: Bigger Test—those who fail become executives and military leaders
  • age 30-35: only now is philosophy taught, i.e. the disciplined seeing of the forms (generalizations, regularities, ideals, laws)
  • age 35-50: Bigest Test—rejoin the world and survive and thrive there; those who fail stay there; those who pass…
  • age 50: …automatically become rulers

4. Social Organization

System of communism among the philosopher rulers, to guard against corruption

  • no private property, no money
  • provisions for living come from the state
  • communism of men and women (no marriage); some women wooed from other classes, others earn their way in through education—there is no sex barrier
  • sharing of children, to the point that no parent in the ruling class knows precisely who his or her children are, and no one (in theory) cares
  • pacifist in orientation
  1. Other members of the state (those outside of the ruling class) marry and have families in the conventional way.
  2. Military protection is necessary, especially to defend the state from outside interference.

Influence on Christianity

It is arguable that Plato is the most influential of philosophers on Christianity, and especially Christian theology. There are two caveats to bear in mind, however.

  • Plato’s influence was almost always indirect, having been mediated by neo-Platonism, to which we will come when we have studied Aristotle.
  • Plato was adapted and subdued as much as he was accepted and used. The Jewish tradition had many ideas of its own, some of which overcame Plato’s in the development of Christian thought, some of which were overcome, and some of which combined in fascinating ways with Plato’s.

With these qualifications in mind, here are some of the areas of influence.

  • The Apologists: Christian Doctrine as Purified, Definitive Greek Philosophy
  • God as Immutable: Forsaking Hebrew Ideas
  • The (Eventual) Triumph of Dualism: Nature vs. Spirit, Body vs. Mind
  • Creation: Forms are the Creative Thoughts of God; Prepares way for Ex Nihilo; Inspires Neo-Platonic Hierarchy of Being
  • Incarnation: Jesus Christ as Perfect Instantiation of The Logos
  • Society: The Great Accidental Social Experiment Based on the Republic
  • Mysticism: The Beatific Vision (of the Forms)

The information on this page is copyright 1994-2011, Wesley Wildman (basic information here), unless otherwise noted. If you want to use ideas that you find here, please be careful to acknowledge this site as your source, and remember also to credit the original author of what you use, where that is applicable. If you want to use text or stories from these pages, please contact me at the feedback address for permission.