Testing the theory of forms › The largeness regress

The label Third Man appears in Aristotle's criticism of Forms (Metaphysics 990b). In the passage examined here, however, the example is Largeness. Socrates agrees that looking at several large things leads him to recognize one Form through which they are large. Parmenides then asks him to look together at those things and Largeness itself. If the same explanatory procedure applies to that expanded group, a further Largeness appears. Repeating the procedure produces further Forms without end (131e–132b).

We can reconstruct the pressure through three assumptions. Several things that are large call for one Form explaining their largeness. Largeness itself can be included among things that are large. The Form explaining such a collection must be distinct from the members whose shared character it explains. Keeping those assumptions in play generates another explanatory Form each time the previous one joins the collection.

These assumptions should not be compressed into the assertion that the theory is simply inconsistent. Each does a different job. The first demands an explanation of shared character. The second extends a predicate to the explanatory Form itself; we can call this self-predication. The third prevents the same Form from serving as its own explanation within the expanded group. A reader who rejects one premise changes the argument, and must explain why that rejection is available.

The difficulty is also more precise than a fear of infinity. An infinite collection is not contradictory merely because it is infinite. The problem here concerns the intended explanatory role of a unique Form: the procedure repeatedly supplies another Form where Socrates had expected a single unifying explanation. Whether this makes the regress vicious depends on what the explanation was required to accomplish. The text makes the multiplication explicit without offering a completed theory of explanation.

A possible response distinguishes the way a Form is what it is from the way its participants possess a property. Largeness need not be a large object in the same sense as a mountain. That response blocks the easy move to an undifferentiated collection. It also creates a responsibility: explain the difference in predication rather than use a change of meaning only when the objection appears. This is a proposed defense for the reader to assess, not a solution delivered by Socrates at this point.