From the Beginning to Plato

338 PLATO: METAPHYSICS AND EPISTEMOLOGY
Form of Beauty—‘the beautiful’ and ‘beautiful’—as describing and not
merely naming the Form.
4 The definition
(D) The triangle is a three-sided plane figure
specifies the condition an individual must satisfy to be a triangle. But
even if ‘the triangle’ in (D) names a universal, the rest of the sentence does
not describe the universal. That is, (D)—however it should be construed—
does not say that the universal triangle is a three-sided plane figure, is a
triangle, in the way an individual triangle is. But that is just how Plato
understands (D).
This connects with a failure to distinguish different types of general
predication. Supposing there is a Form of Man we could say that
(a) Man is eternal, changeless, etc.
Here properties are attributed to the Form just as they are attributed to
Socrates when I say he is white, henpecked, etc. Man is an entity that is an
eternal thing, etc. But
(b) Man is an animal, mortal, etc.
makes a different sort of claim. Thus, whereas there may be some
plausibility in proposing that (b) means
(c) Every man is an animal, mortal, etc.,
(a) certainly does not mean
(d) Every man is a universal, eternal, etc.
The predications in (a) are true because they are about a Form: all Forms
have those properties. The predications in (b) are true because they are about
the specific concept Man. If the two types of predication are not
distinguished, one might understand the predications in (b) in the same way
as those in (a). Then definitions such as
Man is a rational animal
may make it seem obvious that Man is a man, Triangularity is a triangle,
etc.