the Rathouse
Series of Very Abbreviated Versions of Classical Philosophical Works for Very Busy People.
Chapter 3: Plato’s Theory of  Forms or Ideas

The theory of Forms or Ideas has at least three different but overlapping functions in Plato’s scheme. First, it is central to his theory of knowledge which depends on gaining access to the “essence of things” in the World of Ideas or Unchanging Forms. Second, it provides the regularities that maintain continuity behind the chaos and confusion of an ever-changing world. Thirdly it provides a rationalization for the quest to achieve the unchanging social order which approximates to the Ideal of the State, as it is apprehended in the World of Ideas by the Philosopher King.

For the purpose of this reading it is not necessary to dwell on the details of Popper’s exegesis of the theory of forms or the way Plato used the theory in his sociological analysis and his political program. However to indicate some of the amazing scholarship that underpins the work I will reproduce one of the footnotes to this chapter at the bottom of this page.  Popper wanted to solve some fundamental problems rather than to popularize them but to help the general reader he relegated a great deal of technical material to the notes in the back the book.  In the Plato volume there are 200 pages of text and 120 pages of footnotes in smaller print. In the second volume he apparently got lazy or he felt that time was running out so he only managed 90 pages of notes to accompany 280 pages of text. Some of the notes are full-blooded essays that run for several pages and could have been published as journal articles. These include a critical acount of the early work of Wittgenstein, a suggestion as to how Germany could have been treated after World War I to minimise inconvenience for the people while rendering the nation incapable of launching another war, his first moves towards the theory of metaphysical research programs and a critical essay on "scientific" moral theories.

The chapter contains a section on social engineering which is a topic that is best treated in the discussion of  Utopianism in Chapter 9.

The chapter also contains a preliminary exposition and some criticism of essentialism (pathological obsession with terms), which it may be recalled was the topic that triggered the shelving of The Poverty of Historicism and the writing of The Open Society and its Enemies.

"I use the name methodological essentialism to characterize the view, held by Plato and many of his followers, that it is the task of pure knowledge or ‘science’ to discover and to describe the true nature of things, i.e. their hidden reality or essence. It was Plato’s peculiar belief that the essence of sensible things can be found in other and more real things—in their primogenitors or Forms. Many of the later methodological essentialists, for instance Aristotle, did not altogether follow him in this; but they all agreed with him in determining the task of pure knowledge as the discovery of the hidden nature or Form or essence of things. All these methodological essentialists also agreed with Plato in holding that these essences may be discovered and discerned with the help of intellectual intuition."

So every essence has a name and a definition. For the essentialist there are three ways of  knowing something: (1) to know or recognise the essence, (2) to know the definition and (3) to know the name.

There is a more detailed account of the Aristotelian method of definition by essences in Chapter 11 and in this essay on Essentialism and the Organic State.  The point of Popper’s criticism is that obsession with terms and definitions is one of the most persistent and debilitating errors of method across large tracts of the humanities and social sciences

"Methodological essentialism, i.e. the theory that it is the aim of science to reveal essences and to describe them by means of definitions, can be better understood when contrasted with its opposite, methodological nominalism. Instead of aiming at finding out what a thing really is, and at defining its true nature, methodological nominalism aims at describing how a thing behaves in various circumstances, and especially, whether there are any regularities in its behaviour. In other words, methodological nominalism sees the aim of science in the description of the things and events of our experience, and in an ‘explanation’ of these events, i.e. their description with the help of universal laws. And it sees in our language, and especially in those of its rules which distinguish properly constructed sentences and inferences from a mere heap of words, the great instrument of scientific description; words it considers rather as subsidiary tools for this task, and not as names of essences. The methodological nominalist will never think that a question like ‘What is energy?’ or ‘What is movement?’ or ‘What is an atom?’ is an important question for physics; but he will attach importance to a question like: ‘How can the energy of the sun be made useful?’ or ‘How does a planet move?’ or ‘Under what condition does an atom radiate light?’ And to those philosophers who tell him that before having answered the ‘what is’ question he cannot hope to give exact answers to any of the ‘how’ questions, he will reply, if at all, by pointing out that he much prefers that modest degree of exactness which he can achieve by his methods to the pretentious muddle which they have achieved by theirs."

A  Note on the Notes

Popper included a lot of scholarly detail in notes, some of which were full-sized essays, in small print at the back of the book. Below is a sample note from this chapter, following a para in the text where Popper wrote about the place where Plato located his ideal forms. First the text, then the note. It is interesting to note the image of the "trilolgy" of mother, father and offspring that he employs!

The comparison between the Form or Idea of a class of sensible things and the father of a family of children is developed by Plato in the Timaeus, one of his latest dialogues. It is in close agreement14 with much of his earlier writing, on which it throws considerable light. But in the Timaeus, Plato goes one step beyond his earlier teaching when he represents the contact of the Form or Idea with the world of space and time by an extension of his simile. He describes the abstract ‘space’ in which the sensible things move (originally the space or gap between heaven and earth) as a receptacle, and compares it with the mother of things, in which at the beginning of time the sensible things are created by the Forms which stamp or impress themselves upon pure space, and thereby give the offspring their shape. ‘We must conceive’, writes Plato, ‘three kinds of things: first, those which undergo generation; secondly, that in which generation takes place; and thirdly, the model in whose likeness the generated things are born. And we may compare the receiving principle to a mother, and the model to a father, and their product to a child.’ And he goes on to describe first more fully the models—the fathers, the unchanging Forms or Ideas: ‘There is first the unchanging Form which is uncreated and indestructible,.. invisible and imperceptible by any sense, and which can be contemplated only by pure thought.’ To any single one of these Forms or Ideas belongs its offspring or race of sensible things, ‘another kind of things, bearing the name of their Form and resembling it, but perceptible to sense, created, always in flux, generated in a place and again vanishing from that place, and apprehended by opinion based upon perception’. And the abstract space, which is likened to the mother, is described thus: ‘There is a third kind, which is space, and is eternal, and cannot be destroyed, and which provides a home for all generated things ...’15

15 The quotations are from the Timaeus, 50c/d and 51e-52b. The simile which describes the Forms or Ideas as the fathers, and Space as the mother, of the sensible things, is important and has far-reaching connections. Cp. also notes 17 and 19 to this chapter, and note 59 to chapter 10.
(1) It resembles Hesiod’s myth of chaos, the yawning gap (space; receptacle) which corresponds to the mother, and the God Eros, who corresponds to the father or to the Ideas. Chaos is the origin, and the question of the causal explanation (chaos = cause) remains for a long time one of origin (archē) or birth or generation.
(2) The mother or space corresponds to the indefinite or boundless of Anaximander and of the Pythagoreans. The Idea, which is male, must therefore correspond to the definite (or limited) of the Pythagoreans. For the definite, as opposed to the boundless, the male, as opposed to the female, the light, as opposed to the dark, and the good, as opposed to the bad, all belong to the same side in the Pythagorean table of opposites. (Cp. Aristotle’s Metaphysics, 96a22 f.) We also can therefore expect to see the Ideas associated with light and goodness. (Cp. end of note 32 to chapter 8.)
(3) The Ideas are boundaries or limits, they are definite, as opposed to indefinite Space, and impress or imprint (cp. note 17 (2) to this chapter) themselves like rubber-stamps, or better, like moulds, upon Space (which is not only space but at the same time Anaximander’s unformed matter—stuff without property), thus generating sensible things. * J. D. Mabbott has kindly drawn my attention to the fact that the Forms or Ideas, according to Plato, do not impress themselves upon Space but are, rather, impressed or imprinted upon it by the Demiurge. Traces of the theory that the Forms are ‘causes both of being and of generation (or becoming)’ can be found already in the Phaedo (100d), as Aristotle points out (in Metaphysics 1080a2).*
(4) In consequence of the act of generation, Space, i.e. the receptacle, begins to labour, so that all things are set in motion, in a Heraclitean or Empedoclean flux which is really universal in so far as the movement or flux extends even to the framework, i.e. (boundless) space itself. (For the late Heraclitean idea of the receptacle, cp. the Cratylus, 412d.)
(5) This description is also reminiscent of Parmenides’ ‘Way of Delusive Opinion’, in which the world of experience and of flux is created by the mingling of two opposites, the light (or hot or fire) and the dark (or cold or earth). It is clear that Plato’s Forms or Ideas would correspond to the former, and space or what is boundless to the latter; especially if we consider that Plato’s pure space is closely akin to indeterminate matter.
(6) The opposition between the determinate and indeterminate seems also to correspond, especially after the all-important discovery of the irrationality of the square root of two, to the opposition between the rational and the irrational. But since Parmenides identifies the rational with being, this would lead to an interpretation of space or the irrational as non-being. In other words, the Pythagorean table of opposites is to be extended to cover rationality, as opposed to irrationality, and being, as opposed to non-being. (This agrees with Metaphysics, 1004b27, where Aristotle says that ‘all the contraries are reducible to being and non-being’; 1072a31, where one side of the table—that of being—is described as the object of (rational) thought; and 1093b13, where the powers of certain numbers—presumably in opposition to their roots—are added to this side. This would further explain Aristotle’s remark in Metaphysics, 986b27; and it would perhaps not be necessary to assume, as F. M. Cornford does in his excellent article ‘Parmenides’ Two Ways’, Class. Quart., XVII, 1933, p. 108, that Parmenides, fr. 8, 53/54, ‘has been misinterpreted by Aristotle and Theophrastus’; for if we expand the table of opposites in this way, Cornford’s most convincing interpretation of the crucial passage of fr. 8 becomes compatible with Aristotle’s remark.)
(7) Cornford has explained (op. cit., 100) that there are three ‘ways’ in Parmenides, the way of Truth, the way of Not-being, and the way of Seeming (or, if I may call it so, of delusive opinion). He shows (101) that they correspond to three regions discussed in the Republic, the perfectly real and rational world of the Ideas, the perfectly unreal, and the world of opinion (based on the perception of things in flux). He has also shown (102) that in the Sophist, Plato modifies his position. To this, some comments may be added from the point of view of the passages in the Timaeus to which this note is appended.
(8) The main difference between the Forms or Ideas of the Republic and those of the Timaeus is that in the former, the Forms (and also God; cp. Rep., 380d) are petrified, so to speak, while in the latter, they are deified. In the former, they bear a much closer resemblance to the Parmenidean One (cp. Adam’s note to Rep., 380d28, 31), than in the latter. This development leads to the Laws, where the Ideas are largely replaced by souls. The decisive difference is that the Ideas become more and more the starting points of motion and causes of generation, or as the Timaeus puts it, fathers of the moving things. The greatest contrast is perhaps between the Phaedo, 79e: ‘The soul is infinitely more like the unchangeable; even the most stupid person would not deny that’ (cp. also Rep., 585c, 609b f.), and the Laws, 895e/896a (cp. Phaedrus, 245c ff.): ‘What is the definition of that which is named “soul”? Can we imagine any other definition than .. “The motion that moves itself”?’ The transition between these two positions is, perhaps, provided by the Sophist (which introduces the Form or Idea of motion itself) and by the Timaeus, 353, which describes the ‘divine and unchanging Forms and the changing and corruptible bodies. This seems to explain why, in the Laws (cp. 894d/e), the motion of the soul is said to be ‘first in origin and power’ and why the soul is described (966e) as ‘the most ancient and divine of all things whose motion is an ever-flowing source of real existence’. (Since, according to Plato, all living things have souls, it may be claimed that he admitted the presence of an at least partly formal principle in things; a point of view which is very close to Aristotelianism, especially in the presence of the primitive and widespread belief that all things are alive.) (Cp. also note 7 to chapter 4.) (a) In this development of Plato’s thought, a development whose driving force is to explain the world of flux with the help of the Ideas, i.e. to make the break between the world of reason and the world of opinion at least understandable, even though it cannot be bridged, the Sophist seems to play a decisive role. Apart from making room, as Cornford mentions (op. cit., 102), for the plurality of Ideas, it presents them, in an argument against Plato’s own earlier position (248a ff.): (a) as active causes, which may interact, for example, with mind; (b) as unchanging in spite of that, although there is now an Idea of motion in which all moving things participate and which is not at rest; (c) as capable of mingling with one another. It further introduces ‘Not-being’, identified in the Timaeus with Space (cp. Cornford, Plato’s Theory of Knowledge, 1935, note to 247), and thus makes it possible for the Ideas to mingle with it (cp. also Philolaus, fr. 2, 3, 5, Diels5), and to produce the world of flux with its characteristic intermediate position between the being of Ideas and the not-being of Space or matter.
(10) Ultimately, I wish to defend my contention in the text that the Ideas are not only outside space, but also outside time, though they are in contact with the world at the beginning of time. This, I believe, makes it easier to understand how they act without being in motion; for all motion or flux is in space and time. Plato, I believe, assumes that time has a beginning. I think that this is the most direct interpretation of Laws, 721c: ‘the race of man is twin-born with all time’, considering the many indications that Plato believed man to be created as one of the first creatures. (In this point, I disagree slightly with Cornford, Plato’s Cosmology, 1937, p. 145, and pp. 26 ff.)
(11) To sum up, the Ideas are earlier and better than their changing and decaying copies, and arc themselves not in flux. (See also note 3 to chapter 4.)

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