I'm reading about the third man argument here:


One of the properties of forms that's given is "self-predication". I'm having trouble understanding what it is even saying. What does it mean to say that the form of blue-ness is itself blue?

To me the natural solution to the third man argument is throwing out self-predication as a principle of forms.

What were Plato's reasons for having self-predication in the theory of forms? And what is the view of philosophers since on self-predication?

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    It seems dispensable enough, but alas, throwing it out creates another problem: if F is devoid of what imparts things with F-ness then how exactly does it do the imparting? This seems counterintuitive to us mainly because of modern nominalsitic stereotypes, where "blueness" is but a label. But the whole point of Plato's forms was to explain identical F-ness in different things. If F is not responsible for it, what good is it? There is a whole book on the subject, Apolloni, The Self-Predication Assumption in Plato.
    – Conifold
    Commented May 1, 2020 at 5:50
  • When you say explain do you mean a 'causal' explanation? ie: Plato was saying that forms cause objects to have certain properties? So would this issue remain for any type of existence of universals... or is it specific to Plato's forms? Commented May 1, 2020 at 6:43
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    In Partmenides Plato's keyword is "partake", sensibles partake in the forms, he does not operate with modern notions like causality. Other verbs used are "participate" and "imitate" if that helps. I think deep down platonists' paradigm of a form is some sort of "ideal image" purified of contingent imperfections, to this day. Even though modern ones might add "up to isomorphism". In Aristotelian theories forms (common natures) are not detached from their matter in substances, so the linkage is not an issue, and modern theories of abstracta are borderline nominalist in their thin realism.
    – Conifold
    Commented May 1, 2020 at 7:42
  • Platonistic form realm is non spatial-temporal-causal posited to exist independent of our causal physical world (if our world ontically exists at all). At the tip of a cone there may be infinitely such forms right now. Self-predication is simply expressed axiomatically as F(G)=G, where F(g)=G without TMA issue. Regarding what really imparts things with greatness from the form of greatness, it's not really the case here since the form of greatness is not the ultimate ideal form, only up to the math-like ideal form we can measure and thus impart (as forcing) greatness in terms of quantity... Commented Apr 25, 2021 at 23:42

4 Answers 4


The Parmenides section says something about that, i will make a little example Think of all things red, they all share that in common, redness, now, that redness shares something in common with all things red, so a new kind of redness arises, and so on, ad infinitum.

when would you end? will you have the correct definition of redness that makes all thing red red?

  • "redness shares something in common with all things red"... But is that sufficient to say that they have a form in common? Commented May 1, 2020 at 3:57
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    separate both red that participates and the abstract red, then if you make the latter the red that makes all things red red, it participates, and it is of the former kind, you need another red Commented May 1, 2020 at 4:06

Though any general predicate might correspond to a Form (according to Plato's view at one stage or another), and the question of self-predication might be approached in general, Plato more specifically needs to uphold his view that the Form of the Good is itself good, is "greater in dignity and might" than all other Forms. If he wants to say this, he has to then confront the consequences of such self-predication more broadly.

Down the line, one approach to resolving the issue arose in theology, in the notion of analogical predication. Allow (loosely or not) that God is the Form of the Good, but that God is essentially different from creatures. So the goodness of a creature comes from participating in the will of God (in the appropriate way), but the "goodness" of God is actually something like "supergoodness," an internally different predicate. From the SEP article on medieval theories of analogy (sec. 6):

Despite the vast modern literature devoted to Aquinas’s theory of analogy, he has very little to say about analogy as such. He uses a general division into equivocal, univocal, and analogical uses of terms, and he presents both of the threefold divisions of analogy mentioned in the previous section, but he offers no prolonged discussion, and he writes as if he is simply using the divisions, definitions, and examples with which everyone is familiar. His importance lies in the way he used this standard material to present an account of the divine names, or how it is we can meaningfully use such words as ‘good’ and ‘wise’ of God.

The background to this account has to be understood in terms of Aquinas’s theology and metaphysics. Three doctrines are particularly important. First, there is the distinction between being existent, good, wise, and so on, essentially, and being existent, good, wise, and so on, by participation. God is whatever he is essentially, and as a result he is existence itself, goodness itself, wisdom itself. Creatures are existent, good, wise, only by sharing in God’s existence, goodness, and wisdom, and this sharing has three features. It involves a separation between the creature and what the creature has; it involves a deficient similarity to God; and it is based on a causal relation. What is essentially existent or good is the cause of what has existence or goodness by participation. Second, there is the general doctrine of causality according to which every agent produces something like itself. Agent causality and similarity cannot be separated. Third, there is Aquinas’s belief that we are indeed entitled to claim that God is existent, good, wise, and so on, even though we cannot know his essence.

Against this background, Aquinas asks how we are to interpret the divine names. He argues that they cannot be purely equivocal, for we could not then make intelligible claims about God. Nor can they be purely univocal, for God’s manner of existence and his relationship to his properties are sufficiently different from ours that the words must be used in somewhat different senses. Hence, the words we use of God must be analogical, used in different but related senses. To be more precise, it seems that such words as ‘good’ and ‘wise’ must involve a relationship to one prior reality, and they must be predicated in a prior and a posterior sense, for these are the marks of analogical terms.

Nonetheless, the divine names do not function exactly like ordinary analogical terms such as ‘healthy’. We need to begin by making use of the distinction between the thing signified (a nature or property) and the mode of signifying. All the words we use have a creaturely mode of signifying in that they imply time and composition, neither of which can pertain to God. When speaking of God, we must recognize this fact, and attempt to discount it. To say “God is good” is not to imply that God has a separable property, goodness, and that he has it in a temporally limited way. God is eternally identical to goodness itself. But even when we have discounted the creaturely mode of signifying, we are left with the fact that God’s goodness is not like our goodness. This is where the analogy of attribution enters the picture.


The whole discussion about self predication is annihilated when one pauses to reflect that Form is a replacement for the Greek word Idea. Modern philosophy put extra emphasis that Ideas are a whole world different from ordinary things. It took "Idea" to be close enough to "notion" or "concept".

Rep. Bk VI. 507c

"And the one class of things we say can be seen but not thought, while the ideas can be thought but not seen.

So, Ideas are aniconic signs that do not have anything in common with the things that fall within their designation, just as the word "man" has nothing in common with the featherless bipeds meant by it.

Obviously the thought about largeness is not large and more generally ideas derived from sensible qualities would not bear meaningful self predication. So the problem about self-predication is a typical regressive development such as scholasticism exhibited when it speculated on faulty translations. People like Harold Cherniss or Sir W.D. Ross have kept the original Greek word Idea in their studies.

  • Hmmm... in the modern sense we take "Form" to mean "concept" or "notion"... but Plato meant something else by it? Commented Mar 24, 2021 at 23:23

I'm guessing he's saying that you can't know what the truth is because your part of the equation by default, because it's what aristotle says when he throws in 2 cents, says plato expressed greatness, so I guess again that he also pretends or feigns to have have different opinions than his own by impersonating someone for example or proof of greatness via "I'm one way your another" enter aristotle's opinion which leaves u in awe reinforcing and preserving the weight of positive over negative life by making your opinion matter because it's an endless loop of if u or someone else is or isn't there an leaving that life is mysterious an worthwhile with or without u as a theme.

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