Notes on Operationalism

• A property or thing is said to be observable iff the presence of that thing or quality is detectable without instruments



• An observation term is a term referring to an observable thing or property



• A theoretical term is a non-observation term



• An operational definition is a definition of a theoretical terms in terms of one or more observation terms (but not theoretical terms)



• Operationalism is the doctrine that all theoretical terms must have operational definitions. Prominent advocates: Bridgeman in physics, Skinner and Watson in psychology. Note that operationalism goes far beyond the good advice to carefully specify what your technical terms mean and what criteria you use for them. It requires that theoretical terms are legitimate only if they can be shown not really to be theoretical terms at all.



• Example: Let us try to define "There is an electric field of magnitude q present at point p" in observation terms. Good try:

There is an electric field of magnitude q present at point p iff there is an electric field meter M that is operating correctly and if M were place at p and turned on, then it would read (approximately) q.




• This definition is a failure because 'electric field meter' and 'correctly operating electric field meter' are not observation terms. One can not tell without instruments whether or not something is a correctly operating e. f. m. Worse you can not even determine whether some device normally measures electric fields correctly without some reference to physical theory. To determine that it is operating correctly in a particular setting (no interfering magnetic fields, etc) requires additional reliance on theory.



• Additional problem cited by Boyd: Change in the technology of measurement requires change in the operational definition, hence change in the meaning of the theoretical terms so defined. Instead of "electric field" as or theoretical concept, we will have "Hewlett-Packard Field Meter, model 4578 electric field" and "Techtronix Field Meter, model X50 electric field." Different operational definitions define different concepts of electric field, which can be correlated, but not the same, according to verificationist principles.




Some Positivistic Physicists





"At this stage it becomes important to remember that science is concerned only with observable things and that we can observe an object only by letting it interact with some outside influence."

- Paul Dirac, The Principles of Quantum Mechanics, Oxford, Clarendon Press, 4^th ed., 1958, originally published 1930.

"... it is possible to ask whether there is still concealed behind the statistical universe of perceptions a 'true' universe in which the law of causality would be valid. But such speculation seems to us to be without value and meaningless, for physics must confine itself to the description of the relations between perceptions"-- Werner Heisenberg, "Die Rolle der Unbestimmtheitsrelation in der moderner Physik [The role of the uncertainty principle in modern physics]," Monatshefte für Mathematik und Physik 38 (1931) 365-372