What's Wrong with Mud, Dirt, and Hair?

Socratic Virtue Reconsidered

There has been a good deal of scholarly effort devoted to the question: just how fine-grained, exactly, did Socrates, and then Plato, and, later still, the various figures we call ‘Platonists’, mean for their respective conceptions of ‘Form’ to be?  At the one extreme, characteristic of the neoplatonists, there is only one Form, that of the Good or, tellingly, the One.  At the other extreme, we have reason to think that at least mathematical entities and moral concepts, and perhaps even natural kinds and animal species, deserve their own Form. 

In the Parmenides Plato has Socrates make a rare statement concerning what certainly does not qualify for membership in the realm of the Forms:

Are you also puzzled, Socrates, about cases that might be thought absurd, such as hair or mud or dirt     or any other trivial and undignified objects?... Not at all, said Socrates.  In these cases the things are     just the things we see; it would surely be too absurd to suppose that they have a form (Parmenides  130d).

Why is Socrates less than enthusiastic about the suggestion that mud, dirt, and hair might deserve their own Forms?  And why not a form for excrement?  Fingernails?  One could argue that hairiness is always already taken care of by the form of whatever hirsute creature we may consider; thus a Form of hair is unnecessary just because there are forms for each and every kind of hairy thing.  But what about dirt?  Dirt is not a feature of some other thing, like hair is of hairy creatures.  Dirt is one of the basic ingredients of the world.  Perhaps, one might suggest, the reason why there is not a Form of dirt is the same as the reason why there is not a Form of ugliness: ugliness is not a thing itself, just a deprivation of beauty.  But dirt and ugliness, even if we disdain them equally, are not alike ontologically, in this respect.  For if anything, cleanliness is the member in the ‘dirtiness-cleanliness’ opposition that we obtain through deprivation, i.e., through the removal of dirt.