Encyclopedia of Philosophy: THE THEORY OF IDEAS of PLATO

« THE THEORY OF IDEAS of PLATO Plato's theory arises as follows.

Socrates, Simmias, and Cebes are all called ‘men'; they have it in common that they are all men.

Now when we say ‘Simmias is a man' does the word ‘man' stand for something in the way that the word ‘Simmias' stands for the individual man Simmias? If so, what? Is it the same thing as the word ‘man' stands for in the sentence ‘Cebes is a man'? Plato's answer is yes: in each case in which such an expression occurs it stands for the same thing, namely, that which makes Simmias, Cebes, and Socrates all men.

This is given by Plato various designations, Greek phrases corresponding for instance to ‘the man himself', or ‘that very thing which is man'. Because, in calling Socrates a man, Plato meant not that he was male, but that he was human, the common thing meant by ‘man' can be called – by analogy with Plato's use in other cases – ‘humanity'.

But its best known designation is ‘The Idea (or Form) of Man'. Generalizing, in any case where A,B,C, are all F, Plato is likely to say that they are related to a single Idea of F. Sometimes he states the principle universally, sometimes, in particular cases, he hesitates about applying it.

In various places he lists Ideas of many different types, such as the Idea of Good, the Idea of Bad, the Idea of Circle, the Idea of Being, the Idea of Sameness.

And as long as he held the theory at all Plato seems to have continued to believe in the Ideas of Good and Beauty and Being.

But he seems to have been unsure whether there was an Idea of Mud. If we search through the Platonic texts, we discover a number of theses about Ideas and their relations to ordinary things in the world. (1) Wherever several things are F, this is because they participate or imitate a single Idea of F. (2) No Idea is a participant or imitator of itself. (3) (a) The Idea of F is F.

(b) The Idea of F is nothing but F. (4) Nothing but the Idea of F is really and truly altogether F. (5) Ideas are not in space or time, they have no parts and do not change, they are not perceptible to the senses. Theses (1), (2) and (3) make up an inconsistent triad.

The difficulty to which they lead was first expounded by Plato himself in the Parmenides.

Let us suppose we have a number of individuals each of which is F.

Then, by (1), there is an Idea of F.

This, by (3), is itself F.

But now the Idea of F and the original F things make up a new collection of F things.

By (1) again, this must be because they participate in an Idea of F.

But, by (2), this cannot be the Idea first postulated.

So there must be another Idea of F; but this in its turn, by (3), will be F; and so on ad infinitum.

So, against (1), there will be not a single Idea but infinitely many. The problem can be illustrated by substituting ‘Man' for ‘F' in the above pattern of argument.

If there are a number of men, then, by (1) there is an Idea of Man.

But this, by (3) is itself man.

The Idea of Man, plus the original men, therefore form a new collection of men.

By (1), therefore, there must be an Idea of Man to correspond to this collection.

But, by (2) this cannot be the Idea we have already met; so it must be a new Idea.

But this, in its turn, will be another man; and so on ad infinitum; we cannot stop just with one or two Ideas of Man.

Aristotle was to call this refutation of the Theory of Ideas ‘The Third Man argument'.

The problem was never resolved by Plato; and, as already said, it is a matter of dispute between scholars whether he shrugged the objection off or abandoned all or part of his theory as a consequence. The problem to which Plato's theory is an inadequate solution is sometimes called ‘the problem of universals'.

In modern discussions of this problem, four notions can be discerned which bear some resemblance to Plato's Ideas. (A) Concrete Universals.

In a sentence such as ‘water is fluid' the word ‘water' is treated by some philosophers as the name of a single scattered object, the aqueous part of the world, made up of puddles, rivers, lakes and so on. Such a concrete universal would have a certain similarity with Plato's Ideas.

It would explain Plato's preference (not always shared by his commentators) for referring to his Ideas by a concrete mode of speech (e.g.

‘the beautiful') rather than an abstract one (‘beauty').

It would give a clear sense to his theory that particulars participate in Ideas: this particular bottle of water is quite literally a part of all-thewater-in-the-world.

Theses (2), (3a) and (4) are easily shown to be true.

However, a concrete universal is very unlike a Platonic Idea in respect of (3b) and (5) – the water in the universe can be located and can change in quantity and distribution, it can be seen and touched, and has many other properties besides that of being water. (B) Paradigms.

It has more than once been suggested that Platonic forms might be looked on as paradigms or standards: the relation between individuals and Ideas may be thought to be similar to that between particular metre-long objects and the Standard Metre in Paris by which the metre length was formerly defined.

This brings out well the imitation and resemblance aspect of Plato's theory: to be a metre long is, precisely, to resemble in length the Standard Metre; and if two things are each a metre long it is in virtue of this common resemblance to the paradigm.

Like a concrete universal, a paradigm object fits those aspects of Plato's ideas which make them seem substantial entities; like a concrete universal, it fails to have the properties by which Platonic Ideas transcend the sensible world.

The Standard Metre is not in heaven, but in Paris, and is discerned not by intellectual vision but by the eyes in one's head. (C) Attributes and Properties.

Logicians sometimes talk of attributes, such as humanity, or the property of being divisible by seven.

These abstract entities share the more transcendental aspects of Plato's ideas; humanity does not grow or die as human beings do, and nowhere in the world could one view or handle divisibility by seven.

All men, we might say, are human by virtue of sharing a common humanity; this humanity, we might say, is the attribute for which the predicate ‘.

.

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is a man' stands in the sentences ‘Peter is a man' and ‘John is a man'.

But if we think of Platonic ideas in this way as attributes, it is very hard to see how Plato could ever have thought that humanity itself, and only humanity itself, was really a human being.

Is it not clear that humanity is an abstraction,. »