Theory of forms

 ( Idealism ) 

A Form is an objective "blueprint" of perfection.For example, Timaeus 28: "The work of the creator, whenever he looks to the unchangeable and fashions the form and nature of his work after an unchangeable pattern, must necessarily be made fair and perfect ...." The Forms are perfect and unchanging representations of objects and qualities. For example, the Form of beauty or the Form of a triangle. For the form of a triangle say there is a triangle drawn on a blackboard. A triangle is a polygon with 3 sides. The triangle as it is on the blackboard is far from perfect. However, it is only the intelligibility of the Form "triangle" that allows us to know the drawing on the chalkboard is a triangle, and the Form "triangle" is perfect and unchanging. It is exactly the same whenever anyone chooses to consider it; however, time only affects the observer and not the triangle. It follows that the same attributes would exist for the Form of beauty and for all Forms.

Plato explains how we are always many steps away from the idea or Form. The idea of a perfect circle can have us defining, speaking, writing, and drawing about particular circles that are always steps away from the actual being. The perfect circle, partly represented by a curved line, and a precise definition, cannot be drawn. The idea of the perfect circle is discovered, not invented.

It would be a mistake to take Plato's imagery as positing the intelligible world as a literal physical space apart from this one."No sensible man would insist that these things are as I have described them..." ( Phd. 114d)."there is no Platonic 'elsewhere', similar to the Christian 'elsewhere'." (Iris Murdoch, "Metaphysics as a Guide to Morals" (London, Chatto & Windus 1992) 399). Plato emphasizes that the Forms are not beings that extend in space (or time), but subsist apart from any physical space whatsoever. Thus we read in the Symposium of the Form of Beauty: "It is not anywhere in another thing, as in an animal, or in earth, or in heaven, or in anything else, but itself by itself with itself," (211b). And in the Timaeus Plato writes: "Since these things are so, we must agree that that which keeps its own form unchangingly, which has not been brought into being and is not destroyed, which neither receives into itself anything else from anywhere else, nor itself enters into anything anywhere, is one thing," (52a, emphasis added).

But if the very nature of knowledge changes, at the time when the change occurs there will be no knowledge, and, according to this view, there will be no one to know and nothing to be known: but if that which knows and that which is known exist ever, and the beautiful and the good and every other thing also exist, then I do not think that they can resemble a process of flux, as we were just now supposing.

Plato believed that long before our bodies ever existed, our souls existed and inhabited heaven, where they became directly acquainted with the forms themselves. Real knowledge, to him, was knowledge of the forms. But knowledge of the forms cannot be gained through sensory experience because the forms are not in the physical world. Therefore, our real knowledge of the forms must be the memory of our initial acquaintance with the forms in heaven. Therefore, what we seem to learn is in fact just remembering.Kidder, D. S. and Oppenheim, N. D, (2006), The Intellectual Devotional, p. 27, Borders Group, Inc, Ann Arbor.

... when a man has discovered the instrument which is naturally adapted to each work, he must express this natural form, and not others which he fancies, in the material ....

Perceived circles or lines are not exactly circular or straight, and true circles and lines could never be detected since by definition they are sets of infinitely small points. But if the perfect ones were not real, how could they direct the manufacturer?

Nay, but the idea may be like the day which is one and the same in many places at once, and yet continuous with itself; in this way each idea may be one and the same in all at the same time.

But exactly how is a Form like the day in being everywhere at once? The solution calls for a distinct form, in which the particular instances, which are not identical to the form, participate; i.e., the form is shared out somehow like the day to many places. The concept of "participate", represented in Greek by more than one word, is as obscure in Greek as it is in English. Plato hypothesized that distinctness meant existence as an independent being, thus opening himself to the famous third man argument of Parmenides,The name is from Aristotle, who says in Metaphysics A.IX.990b.15: "(The argument) they call the third man." A summary of the argument and the quote from Aristotle can be found in the venerable Grote points out that Aristotle lifted this argument from the Parmenides of Plato; certainly, his words indicate the argument was already well-known under that name. which proves that forms cannot independently exist and be participated.Analysis of the argument has been going on for quite a number of centuries now and some analyses are complex, technical and perhaps tedious for the general reader. Those who are interested in the more technical analyses can find more of a presentation in and

If universal and particulars – say man or greatness – all exist and are the same then the Form is not one but is multiple. If they are only like each other then they contain a form that is the same and others that are different. Thus if we presume that the Form and a particular are alike then there must be another, or third Form, man or greatness by possession of which they are alike. An would then result; that is, an endless series of third men. The ultimate participant, greatness, rendering the entire series great, is missing. Moreover, any Form is not unitary but is composed of infinite parts, none of which is the proper Form.

The young Socrates did not give up the Theory of Forms over the Third Man but took another tack, that the particulars do not exist as such. Whatever they are, they "mime" the Forms, appearing to be particulars. This is a clear dip into representationalism, that we cannot observe the objects as they are in themselves but only their representations. That view has the weakness that if only the mimes can be observed then the real Forms cannot be known at all and the observer can have no idea of what the representations are supposed to represent or that they are representations.

Socrates' later answer would be that men already know the Forms because they were in the world of Forms before birth. The mimes only recall these Forms to memory.Plato to a large extent identifies what today is called insight with recollection: "whenever on seeing one thing you conceived another whether like or unlike, there must surely have been an act of recollection?" – Phaedo, paragraph 229. Thus geometric reasoning on the part of persons who know no geometry is not insight but is recollection. He does recognize insight: "... with a sudden flash there shines forth understanding about every problem ..." (with regard to "the course of scrutiny") – The Seventh Letter 344b. Unfortunately the hidden world can in no way be verified in this world and its otherworldliness can only be a matter of speculation. Plato was aware of the problem: "How real existence is to be studied or discovered is, I suspect, beyond you and me." – Cratylus, paragraph 439.

Plato distinguished between real and non-real "existing things", where the latter term is used of substance. The figures that the artificer places in the gold are not substance, but gold is. Aristotle stated that, for Plato, all things studied by the sciences have Form and asserted that Plato considered only substance to have Form. Uncharitably, this leads him to something like a contradiction: Forms existing as the objects of science, but not-existing as substance. Scottish philosopher W.D. Ross objects to this as a mischaracterization of Plato.Ross, Chapter XI, initial.

Plato did not claim to know where the line between Form and non-Form is to be drawn. As Cornford points out,Pages 82–83. those things about which the young Socrates (and Plato) asserted "I have often been puzzled about these things" Parmenides, paragraph 130c. (in reference to Man, Fire and Water), appear as Forms in later works. However, others do not, such as Hair, Mud, Dirt. Of these, Socrates is made to assert, "it would be too absurd to suppose that they have a Form."

Ross also objects to Aristotle's criticism that Form Otherness accounts for the differences between Forms and purportedly leads to contradictory forms: the Not-tall, the Not-beautiful, etc. That particulars participate in a Form is for Aristotle much too vague to permit analysis. By one way in which he unpacks the concept, the Forms would cease to be of one essence due to any multiple participation. As Ross indicates, Plato didn't make that leap from "A is not B" to "A is Not-B." Otherness would only apply to its own particulars and not to those of other Forms. For example, there is no Form Not-Greek, only particulars of Form Otherness that somehow suppress Form Greek.

Regardless of whether Socrates meant the particulars of Otherness yield Not-Greek, Not-tall, Not-beautiful, etc., the particulars would operate specifically rather than generally, each somehow yielding only one exclusion.

Plato had postulated that we know Forms through a remembrance of the soul's metempsychosis and Aristotle's arguments against this treatment of epistemology are compelling. For Plato, particulars somehow do not exist, and, on the face of it, "that which is non-existent cannot be known". Posterior Analytics 71b.25. See Metaphysics III 3–4.Book III Chapters 3–4, paragraphs 999a ff.

Scholasticism was a highly multinational, polyglottal school of philosophy, and the nominalist argument may be more obvious if an example is given in more than one language. For instance, are strongly variable by language; some languages consider blue and green the same colour, others have monolexemic terms for several shades of blue, which are considered different; other languages, like the Mandarin qing denote both blue and black. The German word "Stift" means a pen or a pencil, and also anything of the same shape. The English "pencil" originally meant "small paintbrush"; the term later included the silver rod used for silverpoint. The German "Bleistift" and "Silverstift" can both be called "Stift", but this term also includes felt-tip pens, which are clearly not pencils.

The shifting and overlapping nature of these concepts makes it easy to imagine them as mere names, with meanings not rigidly defined, but specific enough to be useful for communication. Given a group of objects, how is one to decide if it contains only instances of a single Form, or several mutually exclusive Forms?

• Archetype
• Divided line
• Divine embodiment
• Dmuta in Mandaeism
• Exaggerated realism
• Form of the Good
• Hyperuranion
• Idealism
• Jungian archetypes
• Map–territory relation
• Nominalism
• Plotinus
• Problem of universals
• Substantial form
• Platonic solid
• Plato's unwritten doctrines, for debates over Forms and Plato's higher, esoteric theories
• Realism (disambiguation)
• True form (Taoism)

• Meno: 71–81, 85–86: The discovery (or "recollection") of knowledge as latent in the soul, pointing forward to the theory of Forms
• Phaedo

73–80: The theory of recollection restated as knowledge of the Forms in soul before birth in the body,109–111: The myth of the afterlife, 100c: The theory of absolute beauty

• Symposium: 210–211: The archetype of Beauty.
• Phaedrus: 248–250: Reincarnation according to knowledge of the true, 265–266: The unity problem in thought and nature.
• Cratylus: 389–390: The archetype as used by craftsmen, 439–440: The problem of knowing the Forms.
• Theaetetus: 184–186: Universals understood by mind and not perceived by senses.
• Sophist: 246–259: True essence a Form. Effective solution to participation problem. The problem with being as a Form; if it is participatory then non-being must exist and be being.
• Parmenides: 129–135: Participatory solution of unity problem. Things partake of archetypal like and unlike, one and many, etc. The nature of the participation (Third man argument). Forms not actually in the thing. The problem of their unknowability.
• Republic

* Book III: 402–403: Education the pursuit of the Forms.

* Book V: 472–483: Philosophy the love of the Forms. The philosopher-king must rule.

* Books VI–VII: 500–517: Philosopher-guardians as students of the Beautiful and Just implement archetypical order, Metaphor of the Sun: The sun is to sight as Good is to understanding, Allegory of the Cave: The struggle to understand forms like men in cave guessing at shadows in firelight.

* Books IX–X, 589–599: The ideal state and its citizens. Extensive treatise covering citizenship, government and society with suggestions for imitating the Good, Truth, Justice, etc. Metaphor of the three beds.

• Timaeus: 27–52: The design of the universe, including numbers and physics. Some of its patterns. Definition of matter.
• Philebus: 14–18: Unity problem: one and many, parts and whole.
• Seventh Letter: 342–345: The epistemology of Forms. The Seventh Letter is possibly spurious.

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• Gail Fine (1993). 9780198235491, Oxford: Oxford University Press. ISBN 9780198235491
  Reviewed by
• Gail Fine (2025). 9780199245598, Oxford: Clarendon Press. ISBN 9780199245598
• Matía Cubillo, Gerardo Óscar (2021). " Suggestions on How to Combine the Platonic Forms to Overcome the Interpretative Difficulties of the Parmenides Dialogue", Revista de Filosofía de la Universidad de Costa Rica, vol. 60, 156: 157–171.
• Richard Patterson (1985). 9780915145720, Indianapolis: Hackett Publishing Company. ISBN 9780915145720
• William David Ross (2025). 9780837186351, Oxford: Clarendon Press. ISBN 9780837186351
• Holger Thesleff (2025). 9781930972292, Las Vegas: Parmenides Publishing. ISBN 9781930972292
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