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A Novel Interpretation of Plato’s Theory of Forms


In several recent issues of this journal, I argued for an account of property possession as strict, numerical identity. While this account has stuck some as being highly idiosyncratic in nature, it is not entirely something new under the sun, since as I will argue in this paper, it turns out to have a historic precedent in Plato’s theory of forms. Indeed, the purpose of this paper is twofold. The first is to show that my account of property possession can be utilized to provide a novel interpretation of Plato’s theory of forms. And the second is to show that once it has been divorced from a variety of implausible doctrines with which it has historically been wedded, Plato’s central insight that all properties possess themselves, far from being of mere historical interest, is independently plausible, ironically enough, even from an empirical point of view.

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  1. See my (2005) and (2007). References omitted from the works cited page for the sake of blind review.

  2. In this essay, I will use the term “entity” technically in such a way that an entity is any existing thing, regardless of the ontological category to which it belongs, and I will use the variables “x,” “y,” and “z” to quantify overall entities.

  3. See Dufour (2005). This reference has also been omitted.

  4. The mereological relations of parthood and proper parthood will be defined below.

  5. I do not presuppose that Platonic transcendent realism is equivalent to Plato’s own view. Obviously, I will have more to say about the latter below.

  6. Armstrong attributes this view to John Searle. See Armstrong (1978a, p. 14).

  7. For more on this view, see Armstrong (1978a, pp. 25–27).

  8. Rodriguez-Pereyra attributes this view to David Lewis. See Rodriguez-Pereyra (2002, p. 25, n. 4). Obviously, to avoid the charge of circularity, the class nominalist must insist that this class be “given in extension.” Similar remarks apply to resemblance nominalism.

  9. For a recent defense of resemblance nominalism, see Rodriguez-Pereyra (2002).

  10. For a recent defense of this view, see Bacon (1995).

  11. See my (2007).

  12. Below I will explain why I do not claim that property possession is the relation that x bears to y just in case y is a property that can be truly predicated of x, though probably it is clear enough already.

  13. As I understand the notions, relation R is transitive just in case, for all x, y, and z, if x bears R to y and y bears R to z, then x bears R to z. R is non-transitive just in case, for some but not all x, y, and z, x bears R to y, y bears R to z, and x bears R to z. And R is anti-transitive just in case for all x, y, and z, if x bears R to y, and y bears R to z, then x does not bear R to z. Similar remarks apply with the appropriate changes made to reflexive and symmetrical relations.

  14. This standard interpretation is usually referred to as classical extensional mereology. For more on this interpretation, see Simons (1987).

  15. For example, see Paul (2002).

  16. This is not to say that the nature of this property does not have other properties as proper parts, such as a hue, a shade, etc.

  17. As I explained in my (2007), my account is compatible both with trope theory and with realism about universals, as long as that view is construed in a certain way.

  18. The possession of properties by entities is mind-dependent precisely in those cases in which those properties are possessed by minds.

  19. See also the Phaedo 100c-d, where Plato seems to suggest that the form of beauty is itself beautiful.

  20. I speak to the issue of exactly how to explicate this notion of phenomenon below.

  21. For more on these views, see Rodriguez-Pereyra (2002).

  22. For a discussion of this regress in terms of the form of the Large, see the Parmenides 132a-b.

  23. See the Parmenides 135c, where it seems to be suggested that discourse will be meaningful only if the full plurality of forms exist.

  24. For a discussion semantic relations that obtain between predicates and properties with which I largely agree, see Armstrong (1978b).

  25. See Aristotle’s (1966) Metaphysics book I, chapter 6.

  26. See Timaeus 27d.

  27. For a discussion of this issue that makes Aristotle’s view out to be similar (though not equivalent) to my own, see Spellman (1995).

  28. See Fales (1990, pp. 189–190).

  29. This is what is implied by the claim that properties are shared in common.

  30. See Ehring (2002).

  31. See Fales (1990, p. 191).

  32. As far as I am able to determine, this sentiment can be traced back to Aristotle’s insistence in the Categories that everything other than primary substance can be said of or is present in such substance.


  • Aristotle (translated by Apostle): (1966) Metaphysics, Peripatetic Press

  • Armstrong, David: (1978a) Nominalism and Realism, Cambridge University Press.

  • Armstrong, David: (1978b) A Theory of Universals, Cambridge University Press.

  • Bacon, John: (1995) Universals and Property Instances, Blackwell Press.

  • Ehring, Douglas: (2002) “Spatially Related Universals,” in the Australasian Journal of Philosophy.

  • Fales, Evan: (1990) Causation and Universals, Routledge Press.

  • Paul, L.A. (2002):“Logical Parts” in Nous 36:4 (2002) pp. 578–596.

  • Plato (translated by Hamilton and Cairns): (1961) The Complete Dialogues of Plato, Random House.

  • Rodriguez-Pereyra, Gonzalo (2002): Resemblance Nominalism, Oxford University Press.

  • Simons, Peter: (1987) Parts, Oxford University Press.

  • Spellman, Lynne (1995): Substance and Separation in Aristotle, Cambridge University Press.

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Correspondence to P. X. Monaghan.

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Monaghan, P.X. A Novel Interpretation of Plato’s Theory of Forms. Int Ontology Metaphysics 11, 63–78 (2010).

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  • Proper Part
  • Property Possession
  • Numerical Identity
  • Empirical Point
  • Category Mistake