Definitions demand completeness while indicators reward redundancy

Evidence

The multilevel character of concepts in contrast has received almost no explicit attention. As discussed in the next chapter, the logic varies as one moves up and down the different levels. The logic of definitions is one of completeness and nonredundancy. Going back to Aristotle—and in philosophy in general—a good definition gives the set of necessary and jointly sufficient conditions for a concept. The logic of the data level is usually multiple indicators of one defining dimension. This is a logic of redundancy with no real need for completeness. One wants many—or enough—indicators of a one-dimensional concept: indicators are good when they are redundant. — Gary Goertz, Social Science Concepts and Measurement, 42

Categorization

• DEFINE: Distinguishes two levels of concept logic: definitional (necessary and jointly sufficient conditions) versus data (multiple redundant indicators of one dimension).
• SEED: Angle: why the ‘good indicator’ and ‘good definition’ criteria are opposites — a piece on how the index boom quietly abandoned Aristotelian definitions.