Cumulative Record. Chapter 28: The Operational Analysis of Psychological Terms. Quote 42

To be consistent the psychologist must deal with his own verbal practices by developing an empirical science of verbal behavior. He cannot, unfortunately, join the logician in defining a definition, for example, as a “rule for the use of a term” (Feigl); he must turn instead to the contingencies of reinforcement which account for the functional relation between a term, as a verbal response, and a given stimulus. This is the “operational basis” for his use of terms; and it is not logic but science. (p. 426)