Alexander Nehamas on 'The Imperfection of the Sensible World'

The "approximation" view of Forms is that sensibles are approximations of the Forms. That is, they exhibit approximately the relevant properties which a form exhibits absolutely. I will be calling the "approximation" view of the Forms 'A' for short.

A is a quite common view about forms: Nehamas wants to show why it is wrong and explain a better view.

According to A:

• 1. Plato was prompted by geometry to formulate his theory of Forms. Geometrical objects are intelligible objects: any given instantiation in sensible form is not what geometry is really about.
• 2. Sensible objects approximate intelligible objects like equal, circle, square. The deficiency of the sensible objects lies in the fact that the sensibles can always be made more equal, more circular, etc. Sensible geometrical illustrations are always 'fuzzy' or 'imprecise.'
• 3. Plato applied this same sense of deficiency to ethical and aesthetic objects. So things are never fully just, beautiful, etc. They can always be made more just, beautiful, etc. Thus the Form of beauty, justice, etc. is like the limit of an infinite series.

Note that on A (Approximation view) the sensible beauty is deficient in beauty--there is nothing sensible that is completely beautiful. Another way to put that is that no form is ever fully manifest in a sensible.

Nehamas' view is quite different:

• Instantiations of the Forms in the sensible realm are REALLY equal, beautiful, just, etc.
  
• They possess equality, beauty, justice, etc., however, in only an accidental way. That is why they can be beautiful in one context and ugly in another, for example.
  
• The Form Beauty, however, just is beautiful in any context.

• Things that have Forms are 'incomplete predicates,' which are contrasted with 'complete predicates.'
  
• A complete predicate is something like 'finger,' 'stick,' 'human.' A finger just is a finger in any context, as long as it undergoes no change in itself. A human is a human, fully human.
  
• Incomplete predicates are things like 'just,' 'tall,' 'beautiful,' etc. A thing that is tall in one context is short in another, and yet it underwent no change in itself.
  
• Thus Nehamas also calls incomplete predicates 'accidents': sensible things can only accidentally possess them.
  
• Complete predicates, on the other hand, essentially belong to the objects which possess them.

By introducing Forms for incomplete predicates, Plato solved a problem which Socrates faced: what one thing makes all just or pious things just or pious? He postulated that there are things which are essentially just and essentially pious, and so that it makes sense to call things that instantiate them 'just' or 'pious.'

Problems with A

• it gives us no reason to say that anything sensible is just or pious or equal, for nothing sensible really is just or pious or equal. According to A, things are only more or less just, pious, or equal. If that is so, then we might as well call them unjust, impious, or unequal, because they all fall short of justice, piety, and equality.
• In other words, saying that some particular crooked line is an approximation of straight linearity is just a strange way of talking about a line that is fully and completely whatever crooked line it is. If there are only crooked lines in this world, then why talk of straight at all?
  
• To postulate straightness is just about as justified as postulating the existence of the external world based on sense-experience. Sense-experience just does not give us proof that the external world exists, and neither does crookedness, no matter how close it gets to straight, give us proof that straight exists.

Nehamas' solution allows us to speak of straight lines that are sensible and are straight, and says that we are right to do so.

Also, if Plato meant that the sensible objects resemble the Forms in degrees, why did he never speak of the relationship as one of degree?

(Nehamas has an interpretation of Phaedo 72e-78b. It takes up a large part of the article, and from reading it, I can see that he thinks that the Phaedo supports his view but not A. I think discussing it here would be good, but take too long and not offer any additional payoff. So, if you are curious about Nehamas' full view, as always, go to the source.)

It is clear that he thinks that no earthly equal can appear equal in every relation, and yet Plato wanted to find that one thing that makes every earthly equal equal. That one thing is the Form equality.

• It takes a very strong stand about what there can be Forms of: things that are complete predicates, such as "finger" cannot have a Form, right? Because a finger just is a finger as long as it undergoes no change in itself.
  
• Elsewhere, Plato mentions a lot of things that can have forms, such as mud. Isn't mud a complete predicate?
• Is "table" a complete predicate?
• What about "human"? Is it really 'complete'? Are humans human in any context? There seem to be contexts in which humans are just flesh and bones. Surely the human eating lion just sees a human as food. Even if that's not a perfect example for the point, the question remains: Is the idea of "complete predicates" really coherent?