Cumulative Record. Chapter 28: The Operational Analysis of Psychological Terms. Quote 5

We are told that a concept is to be defined “in terms of” certain operations, that propositions are to be “based upon” operations, that a term denotes something only when there are “concrete criteria for its applicability,” that operationism consists in “referring any concept for its definition to… concrete operations…,” and so on. We may accept expressions of this sort as outlining a program, but they do not provide a general scheme of definition, much less an explicit statement of the relation between concept and operation. (p. 417).