Theory of Forms

  1. Background

    A problem for the Socratic search for definitions: how do you know when a definition is correct? You have to (at least) understand the definition, i.e., you have to understand the terms in the definiens. But how do you do that? By understanding their definitions? This leads to either circularity or an infinite regress.

    The problem arises if we try to give a linguistic account of understanding. The knowledge of a definition according to such an account would have to be propositional knowledge. That is: we explain what X is by offering the definition

    X =df ABC.

    This just invites the question: how do we know that X is ABC? If we answer this by saying that we know what A, B, and C are, and if we have to explain our understanding of A, B, and C in a similar way, there is no way out.

    Plato’s idea: at some point, one must invoke a kind of knowing that is not propositional - i.e., not a matter of knowing that something-or-other - but is more like knowledge by acquaintance. More graphically: one must invoke a kind of knowing that is not a matter of grasping a definition of one term by means of other terms, but of grasping the thing itself.

    This is the way recollection seems to be understood in the Phaedo. Recollection is the epistemological mechanism, and the Forms are the objects to which the mechanism is applied.

    [Plato may be right in rejecting the idea that understanding can be adequately explained in terms of knowing that, but wrong in proposing a kind of knowledge by acquaintance in its place. The proper contrast is not between knowledge by description (knowing that p) and knowledge by acquaintance (knowing x), but between knowing that and knowing how.  That is, having a concept is not a matter of being acquainted with an item available only to the gaze of an intellect, but of having certain abilities and capacities. Cf. Aristotle and Ryle.]

  2. Characteristics of Forms

    1. A general metaphysical and epistemological theory. Central to all of Plato’s thought, but nowhere systematically argued for. Not stated in any one dialogue; we must cull from several (but principally Phaedo and Republic).

    2. A theory of postulated abstract objects, deriving from the Socratic “What is X?” question, which presupposes that there is a single correct answer to the “What is X?” question.

      1. The correct answer is not a matter of convention, of what we all (or most of us) think.
      2. What makes such an answer correct: it is an accurate description of an independent entity, a Form.
      3. Forms are thus mind-independent entities: their existence and nature is independent of our beliefs and judgments about them.

    3. The Phaedo contains an extended description of the characteristics and functions of the forms:

      • Unchangeable (78c10-d9)
      • Eternal (79d2)
      • Intelligible, not perceptible (79a1-5)
      • Divine (80a3, b1)
      • Incorporeal (passim)
      • Causes of being (“The one over the many”) (100c)
      • Are unqualifiedly what their instances are only with qualification (75b)

    4. Other dialogues fill out the picture: non-temporal (Tim. 37e-38a); non-spatial (Phaedr. 247c); they do not become, they simply are (Tim. 27d3-28a3).

    5. Phaedo 80b provides a good summary, listing all the attributes of Forms that souls also have: “divine, deathless, intelligible, uniform, indissoluble, always the same as itself.”

  3. Terminology

    Forms are sometimes called “Ideas” - Plato’s words are eidos and  idea, and the latter suggests the English “idea.” But this gives the wrong idea.

    For Plato’s Forms are not mental entities, nor even mind-dependent. They are independently existing entities whose existence and nature are graspable only by the mind, even though they do not depend on being so grasped in order to exist.

  4. What the Forms do

    The forms are postulated to solve certain philosophical problems:

    1. Epistemological: what are the objects of knowledge? How is knowledge possible? How is knowledge distinguished from (mere) belief or opinion?

      Plato’s objection to the physical universe: it’s Heraclitean (as he conceived Heraclitus’s theory). Objects in flux can’t be known.

    2. Metaphysical: What things are real? Is there a mind-independent reality? Is there anything permanent behind the changing phenomena that can be perceived?

      The two-worlds theory: Cf. the Allegory of the Cave in Republic VII. The intelligible world is Parmenidean, the visible world is Heraclitean. Forms in the intelligible realm are postulated to be the objects of knowledge. The metaphysical theory is thus designed to fit epistemological requirements.

    3. Moral: can there be moral knowledge? Are there objective moral truths? Is morality founded in nature or convention?

      For Plato, goodness and being are intimately connected. Plato’s universe is value-ridden at its very foundations: value is there from the start, not imposed upon an antiseptic, value-neutral reality by the likes of us - external imposers of value on what in itself has no intrinsic value.

      This connection explains why it is a single theory that aims to answer both metaphysical and ethical questions. Understanding how this can be so is one of the hardest - but most important - things to do in understanding Plato.

      The Form of the Good is at the top of the hierarchy of Forms, illuminating all of the others (as the sun illuminates objects in the visible realm, to use Plato’s famous metaphor from the Republic).

      An interpretation of this: knowing what something is can’t be divorced from knowing whether it's good. One can’t know what it is to be an F unless one knows what it is to be a good F: a non-defective example of its kind. Here is one way to see the connection: imagine a good head of lettuce. Now imagine another head of lettuce, but not as good as the first. And so on. There comes a point at which our example becomes so bad that it ceases to be a head of lettuce at all. If there were no connection between goodness and being, there would be no reason to expect this.

    4. Semantical: what do general terms stand for? What is it that we grasp when we understand something? Cf. again the Allegory of the Cave in Republic VII.

  5. Arguments for Existence of Forms

    Plato sometimes writes as if he takes the existence of Forms for granted, as a matter of faith. But sometimes he offers arguments for them. Each argument is connected to a function Plato has in mind for Forms to play. Some of these “reasons” for believing in Forms don’t really add up to arguments, but some do. Plato, in any event, was not very systematic about his arguments.

    1. Forms are objects corresponding to Socratic definitions.
      A Form is supposed to provide an objective basis for moral concepts. A definition is correct just in case it accurately describes a Form. The definition of Justice, e.g., is that statement which correctly tells us What Justice Is.

    2. Forms are objects of recollection.
      The knowledge we get when we are in possession of a Socratic definition is a priori, not empirical. So Forms are the entities for such a priori (= recollectible) truths to be about.

    3. Imperfection argument.
      Forms are the real entities to which the objects of our sensory experience (approximately) correspond. We make judgments about such properties as equal, circular, square, etc., even though we have never actually experienced any of them in perception. Forms are the entities that perfectly embody these characteristics we have in mind even though we have never experienced them perceptually.

    4. Argument from knowledge (“from the sciences”).
      What is our knowledge “about”? When we know something, what is our knowledge knowledge of? Plato supposes that there is a class of stable, permanent, and unchanging objects that warrant our knowledge claims.

    5. One Over Many argument.
      A famous passage in the Republic (596a) suggests a semantic role for the Forms (“there is one Form for each set of many things to which we give the same name”). That is, when you use the word ‘just’ and I use the word ‘just’, what makes it one and the same thing that we’re talking about? Plato’s answer is: the Form of Justice, the “one over the many.”

      Plato believes that there is a non-conventionalist answer to questions of meaning: there is some one thing that is referred to by ‘just’ whenever it is used. Hence, when you talk about justice and I talk about justice, we are talking about the same thing. We belong to the same world, not each of us in his own private world. If we disagree in what we apply the term ‘just’ to, we cannot both be right.

      The last three of these arguments are especially important. They correspond to three of the problems the Forms are supposed to solve. We’ll look at the first of these in the Phaedo, and at the others later.

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Copyright © 2006, S. Marc Cohen