Purposive qualities should always be explained in terms of more basic properties of behavior. Purpose DOES belong among the descriptive qualities of behavior. Intentional, purposive qualities of behavior can be attributed to organisms on the basis of objective criteria, and therefore allow intersubjective consensus. Purposive qualities are emergent, and therefore cannot be explained in terms of more basic qualities of behavior. Theoretical Concepts Theoretical vocabulary should be restricted to operationally defined concepts.
Theoretical concepts are to be linked to the data language through operational definitions.
BUT operationism does not provide suitable criteria for individuation of concepts. Any two things can be considered similar or different in an infinite variety of ways. One cannot know when to ignore differences and consider two things similar, or ignore similarities and consider two things different. There is no unique shorthand summary of observations. YES, BUT distinctions are actually drawn only after the fact, in such a way as to maximize simplicity and comprehensiveness.