Measurement Theory, Psychology and the Revolution That Cannot Happen

Abstract

Doubt is raised that revolutions in measurement theory, for example conjoint measurement or Rasch measurement, will lead to the quantification of psychological attributes. First, the meaning of measurement is explained. Relying on this, it is demonstrated that in order to attain quantification under causally complex circumstances it is necessary to manipulate the phenomena involved and control systematic disturbances. The construction of experimental apparatus is necessary to accomplish these tasks. The creation of modern quantitative science through the adoption of this method is called the Galilean revolution. Next the Millean quantity objection is formulated. If the Galilean revolution is not possible in psychology, the task of quantification is not solvable. The objection is defended. Psychological phenomena are neither manipulable nor controllable to the required extent. Therefore they are not measurable.