The Definition Problem Given: an abstraction knowledge. Problems: 1. develop the facility to accept and store a definition for the abstraction. 2. Given an instance, use the learned definition to determine if the given instance satisfy the definition of a specific abstraction. In other words, answer the question: "Is the given instance the specific abstraction?". e.g., An abstraction knowledge: greatest common factor Problems: 1. Develop an internal "definition" class to allow its definition to be taught and stored. 2. Answer the question, given a reference collection of input and a target, is the target the greatest common factor of the reference collection? Goal: Develop theory and program to teach the definitions of all kinds of knowledge, not just one specific piece of knowledge.